Lecture 23: Precipitation and Agglutination Reactions PDF

Lecture 23 Rest of Chapter 18- Precipitation Reactions (1 of 2) Is common in diagnostic settings, we are looking at a soluble antigen (an antigen in solution not attached to a cell) and we are going to expose it to an to antibody and if the antibody can recognize the antigen there’s a precipitat...

Lecture 23 Rest of Chapter 18- Precipitation Reactions (1 of 2) Is common in diagnostic settings, we are looking at a soluble antigen (an antigen in solution not attached to a cell) and we are going to expose it to an to antibody and if the antibody can recognize the antigen there’s a precipitation reaction, its basically the antibody coming tg with the antigen and it can physically be seen this happening. Precipitation reactions involve the reaction of soluble antigens with IgG or IgM antibodies and within seconds, the antigens and antibodies rapidly form small antigen–antibody complexes and over the course of minutes or hours the antigen- antibody complexes form larger, interlocking aggregates called lattices that precipitate from solution ◦Precipitin reactions only form where the ratio of antigen to antibody is optimal ◦Precipitin ring test: a cloudy line forms where there is the optimal ratio of antigen and antibody. Described as a ring, can see in the test tube and it looks like ring. Figure 18-3 A Precipitation Curve The figure shows that no visible precipitate forms when either component is in excess. Figure- The curve is based on the ratio of antigen to antibody. The maximum amount of precipitate forms in the zone of equivalence, where the ratio is roughly equivalent. looking for zone of equivalence and you have correct amount of antibody and antigen to allow you to see the structure, in the test tube you’ll see it in figure 18-4 Figure 18-4 The Precipitin Ring Test The optimal ratio can be achieved when separate solutions of antigen and antibody are placed adjacent to each other in agar gel (immunodiffusion test) or in solution (precipitin test) If they are allowed to diffuse together, a cloudy line of precipitation will appear in the area in which the optimal ratio has been reached (the zone of equivalence). (a) This drawing shows the diffusion of antigens and antibodies toward each other in a small-diameter test tube. Where they reach equal proportions, in the zone of equivalence, a visible line or ring of precipitate is formed. B- in the test tube shows ring of precipitation. Looks like dust in the liquid. Its a percepetation because the antigen is soluble its not attached to a cell. In the test, a solution containing the antibody is placed at the bottom of a small tube, and the antigen solution is carefully added on top. The two solutions slowly move toward each other. When they meet in the right amounts, they react and form a cloudy ring in the tube. This ring is called the "precipitin ring," and it shows that the antigen and antibody are present and reacting. Figure 18-5 An Agglutination Reaction Agglutination reactions involve either particulate antigens (particles such as cells that carry antigenic molecules) or soluble antigens adhering to particles. These antigens can be linked together by antibodies to form visible aggregates, a reaction called agglutination. Figure- When antibodies react with epitopes on antigens carried on neighboring cells, such as these bacteria, the particulate antigens (cells) agglutinate. IgM, the most efficient immunoglobulin for agglutination, is shown here, but IgG also participates in agglutination reactions. Antibody attaching to the antigen on a cell is agglutination. Is talking about an antigen being part of the cell. IgM can bind 10 different cells or 1 igm can be attaching at different points on 1 cell. Precipitation is talking about a soluble antigen. The Agglutination Reaction Test is a simple lab test to check if specific antigens or antibodies are present in a sample. It works by mixing a sample with antibodies or antigens. If they match, they stick together and form visible clumps. Figure 18-6 Measuring Antibody Titer with the Direct Agglutination Test Direct agglutination tests detect antibodies against relatively large cellular antigens, such as those on red blood cells, bacteria, and fungi. They are usually done in plastic microtiter plates that contain many shallow wells. The amount of particulate antigen in each well is the same, but the amount of serum that contains antibodies is diluted, so that each successive well has half the antibodies of the previous well. The more antibody we start with, the more dilutions it will take to lower the amount to the point where there is not enough antibody for the antigen to react with. For infectious diseases in general, the higher the serum antibody titer, the greater the immunity to the disease. Can use agglutination reaction to get a number of what the concentration of antibody in a persons serum (fluid part of blood, cells are removed), if you wanted to find the concentration of an antibody to an antigen is you can find this out by doing a dilution series of the antibody using wells and do different dilutions of the serum and the antibody is slowly being reduced in concentration and look in the well to see what dilution where you could see the percepetation. You can get an idea than what the concentration of the antibody is. Figure 18-7 Reactions in Indirect Agglutination Tests In indirect (passive) agglutination tests, the antibody reacts with the attached antigen or in reverse by using particles coated with antibodies to detect the antigens against which they are specific. The particles then agglutinate with one another, much as particles do in the direct agglutination tests. Figure- These tests are performed using antigens or antibodies coated onto particles such as minute latex spheres. A- We can do an indirect agglutination test, and instead of having cell with natural antigen, we can physically attach an antigen to in this case a latex bead, the latex bead is taking the place of the cell and its in direct because your making the latex bead hold an antigen, and we can put antibody to see if the antibody can recognize antigen. Can still see agglutination reaction, only thing different is you created the cell by replacing it with the latex bead B- can also reverse it and on the latex bead have the antibody and now were looking for a reaction with an antigen. The Indirect Agglutination Test is a lab technique used to detect antigens or antibodies indirectly by attaching them to tiny particles like beads or red blood cells. These particles make it easier to see the clumping (agglutination) reaction. For example, if testing for a disease, latex beads coated with a specific antigen can be mixed with a sample. If antibodies for that disease are present, the beads will clump together, showing a positive result. Hemagglutination When agglutination reactions involve the clumping of red blood cells, the reaction is called hemagglutination. These reactions involve red blood cell surface antigens and their complementary antibodies. They are used routinely in blood typing and in the diagnosis of infectious mononucleosis. Figure 18-8a Reactions in Neutralization Tests Neutralization is an antigen–antibody reaction in which antibodies block the harmful effects of a bacterial exotoxin or block viruses from infecting cells Such a neutralizing substance, originally called an antitoxin, is a specific antibody produced by the host as it responds to a bacterial infection. The antitoxin binds to the exotoxin and blocks its toxic effect Would like to pull out toxin with the antibody before it attaches to whole cells and destroy it. We make antibodies to toxins to hopefully neutralize the toxin before it attaches to our cells. Neutralization Reactions (2 of 2) Viral hemagglutination occurs when viruses agglutinate R B Cs without an antigen-antibody reaction. Viruses can naturally bind to RBC. It non specifically binds to something on our RBC, we can prevent the hemagglutination by using antibodies that are specific to virus ◦Mumps, measles, influenza does this Viral hemagglutination inhibition test is used for subtyping viruses ◦Is a neutralization test in which antibodies against particular viruses prevent the viruses from clumping red blood cells in vitro. Certain viruses, such as those causing mumps, measles, and influenza, can agglutinate red blood cells without an antigen–antibody reaction—a process called viral hemagglutination ◦Viruses and R B Cs are mixed with the patient's serum ‣ If the serum contains antibodies to a virus, they neutralize the virus and inhibit hemagglutination ‣ If a person’s serum contains antibodies against these viruses, these antibodies will react with the viruses and neutralize them. For example, if hemagglutination occurs in a mixture of measles virus and red blood cells but does not occur when the patient’s serum is added to the mixture, this result indicates that the serum contains antibodies that have bound to and neutralized the measles virus. Figure 18-8 (b) and (c) Reactions in Neutralization and Hemagglutination if we think of this as the influenza virus, the h protein non specifically will see a receptor on our RBC and cause an agglutination and can see this in the test tube. If you know the patients serum has a good chance of being positive for antibodies because it looks like they just recovered from influenza, the antibody taken from patients serum will hopefully grab onto the virus before the virus has a chance to grab onto RBC. This is a test looking for inhibition of normal hemagglutination or neutralization test. Antibodies are specific and you can identify the strain of the influenza virus, since your making antibodies to certain antigens. Complement-Fixation Reactions Complement fixation test shows how complement works and is used to identify a low serum concentration of an antibody. During most antigen–antibody reactions, a complement serum protein binds to (is fixed to) the antigen–antibody complex. This process of complement fixation can be used to detect very small amounts of antibody. Complement fixation: complement serum protein binds to and is fixed to the antigen–antibody complex ◦Detects small amount of antibody. Sensitive and can pick up small amounts of antibodies. ◦Works for antibodies that do not work with precipitation or agglutination reactions ◦Use to diagnose certain viral, fungal, and rickettsial diseases and pathogens. The test is performed in two stages: complement fixation and indicator. Figure 18-9 The Complement-Fixation Test Figure- This test indicates the presence of antibodies to a known antigen. Complement will combine (be fixed) with an antibody that is reacting with an antigen. If all the complement is fixed in the complement-fixation stage, then none remains to cause hemolysis of the red blood cells in the indicator stage. With the complement fixation test, have serum from patient and look to see if they have the antibody for hepatitis virus for example, take the persons serum and add to test tube the antigen of the virus and complement factors and if the antibody is really present for the hepatitis virus we’ll see a complex of the antigen antibody and complment factors, unfortunately when you look at test tube you can’t see the complex, don’t know if you have positive or negative so you have to add a reagent that’s an indicator of a positive or negative result, the indicator is RBC and there’s antibody made to the RBC, you put complex in the test tube, if complment was freely available and wasn’t bound to an antigen and an antibody than the RBC will lyse because you’ll go down the complement cascade and the complement factor will punch holes through a membrane. In this case the RBC stay intact so we must’ve made a complex of the antigens of the virus with the antibody for the patients serum and they tied up all the complement so it wasn’t free to lyse the RBC. Positve result- the patient had hepatitis antibodies so they were recovering and mena the RBC don’t lyse Negative result- if the patient doesnt have antibodies even though there is hepatitis virus with complement there’s is no antibody to make complex so the RBC will be lysed, complement was not tied up with the patients antibody attached to antigen and the RBC lyse. A sample (like blood) is mixed with a known antigen that matches the disease being tested for. If the sample has antibodies for that antigen, they bind together and "fix" the complement, meaning the complement gets used up in this reaction. If no antibodies are present, the complement remains free. To see if the complement was fixed, a second step is done. A mixture of red blood cells and antibodies that cause them to break apart is added. If the complement was used up in the first step, the red blood cells stay intact. If the complement wasn’t used, it will break apart the red blood cells, which is a negative result. Figure 18-10 Fluorescent-Antibody (F A) Techniques Fluorescent-antibody (FA) techniques can identify microorganisms in clinical specimens and can detect the presence of a specific antibody in serum. These techniques combine fluorescent dyes such as fluorescein isothiocyanate (FITC) with antibodies that fluoresce (shine or glow) when exposed to ultraviolet light Can detect antigen a pathogen in someone’s blood, can use fluorescent antibody, Expose sample to fluorescent antibody, the light passing up through your specimen is at a range that excites the floresent dye and lights it up and if its attached to the cells under microscope you’ll see chain of streptococcal organisms light up with the fluorescence coming from the dye that the antibody is attached. It excites the floursent dye. If you don’t have enough antibodies in the serum you can enhance it by adding a second antibody that will recognize any antibody attached or sometimes referred to as anti antibodies. The organism will light up.  Figure- The reaction is viewed through a fluorescence microscope, and the antigen with which the dye-tagged antibody has reacted fluoresces (glows) in the ultraviolet illumination. (a) A direct FA test to identify group A streptococci. (b) In an indirect FA test used in the diagnosis of syphilis, the fluorescent dye is attached to anti-human immune serum globulin, which reacts with any human immunoglobulin (such as the Treponema pallidum–specific antibody) that has previously reacted with the antigen. Direct fluorescent-antibody (FA) tests are usually used to identify a microorganism in a clinical specimen. During this procedure, the specimen containing the antigen to be identified is fixed onto a slide. Fluorescein-labeled antibodies are then added, incubated briefly, and washed to remove any antibody not bound to antigen. Yellow-green fluorescence under the fluorescence microscope from the bound antibody will be visible even if the antigen, such as a virus, is submicroscopic in size. Indirect fluorescent-antibody (FA) tests are used to detect the presence of a specific antibody in serum following exposure to a microorganism (Figure 18.10b). They are often more sensitive than direct tests. A known antigen is fixed onto a slide, and then the test serum added. If antibody that is specific to that microbe is present, it reacts with the antigen to form a bound complex. Enzyme-Linked Immunosorbent Assay (E L I S A) Enzyme immunoassay (E I A)- developed in 1970s There are two basic methods: ◦Direct E L I S A ‣ Can detect antigens or antibodies Sample containing antigens is mixed with antibody ‣ For these tests, antibodies specific for the drug are attached to a well of the microtiter plate. When the patient’s urine sample is added to the well, any of the drug that it contained would bind to the antibody and is captured. The well is rinsed to remove any unbound drug. To make a visible test, more antibodies specific to the drug are now added (these antibodies have an enzyme attached to them—therefore, the term enzyme-linked) and will react with the already-captured drug, forming a “sandwich” of antibody/drug/enzyme-linked antibody. This positive test can be detected by adding a substrate for the linked enzyme; a visible color is produced by the enzyme reacting with its substrate. Used in the detection of the presence of drugs in urine. Enzyme-linked antibodies react with the antigen. Can detect antigens of even antibody’s, can use enzyme linked to it and determine if the antibody ever bound with antigens by seeing if a color is produced. Detected by adding a substrate for the linked enzyme; a color is produced ◦Indirect E L I S A ‣ Detects antibodies  ‣ detects antibodies in a patient’s sample rather than an antigen such as a drug ‣ Indirect ELISA tests are used, for example, to screen blood for antibodies to HIV. ‣ For such a purpose, the microtiter wells contain antigens, such as the inactivated virus that causes the disease the test is designed to diagnose. A sample of the patient’s serum is added to the well; if it contains antibodies against the virus, they will bind the antigen. The well is rinsed to remove unbound antibodies. If antibodies in the serum and the virus in the well have attached to each other, they will remain in the well—a positive test. To make a positive test visible, some anti-HISG (which, again, will attach to any antibody) is added. The anti-HISG is linked to an enzyme. A positive test consists of a “sandwich” of a virus/antibody/enzyme-linked-anti-HISG. At this point, the substrate for the enzyme is added, and a positive test is detected by the color change caused by the enzyme linked to the anti-HISG. A microtiter plate with numerous shallow wells is used in both procedures. Figure 18-12 The E L I S A Method Figure- The components are usually contained in small wells of a microtiter plate We have antibody attached to well, we put in sample and see if antibody that can attach to what it should be recognizing. We have to put in secondary antibody that has an enzyme linked to it. Kinda like a sand witch, 2 antibodies and in between is antigen. Need to add liquid compound that has no color but if the enzyme sees the colorless substrate it it will clip it and is purple solution and is purple and is positive. If the antibody is washed away or not present than the antibody is attached to antigen and there’s no secondary antibody and no color compound so the antigen isn’t present or attached to antibody. B- instead of attaching antibody you can add antigen first People used to use radioactive molecules Rapid Antigen Tests- can be looking for pathogen S A R S-C o V-2 rapid antigen test is also known as lateral flow assay, this allows for the detection of viral antigens by their binding to labeled antibodies, which are in turn attached to a paper strip Nasal swab sample and the swab is then soaked in a solution that disrupts the virus to release its antigens. The extract is applied to the strip, where it migrates by capillary action (lateral flow) through the paper strip. If SARS-CoV-2 antigens are present in the sample, they will be captured by the antigen-specific antibodies and seen as a colored line on the strip, indicating a positive test for COVID-19. ◦If S A R S-C o V-2 antigens are present, as they flow through the strip by capillary action they will be captured by labeled antibody—forming a colored line on the strip Can do for pregnancy Or screening for drugs Figure 10-13 A Rapid At-Home E L I S A Test for S A R S-C o V-2 Is modified Elisa, take sample from nasal swab if you suspect someone has covid for example and have antibodies in there to the antigen on the virus and also have antibody that will have a dye attached so instead of an enzyme we have a dye attached to the antibody. The idea is the antibody with the dye will attach to the virus if present and the liquid works up the strip and waiting at the test line is another antibody that will recognize the virus and if the virus is present than the virus with the dye and antigen will accumulate at the test line and you’ll see the red line, no virus than the liquid will pass test line. Need controlled line to verify that all the reagents are there to make sure theres not a false reading. Big Picture: Vaccine-Preventable Diseases (2 of 5) vaccination increase our life span by a lot because before in the 1900s ppl died of infectious diseases in there 40s. Chapter 19- disorders associated with the immune system talks about hyper sensitivity , when things go wrong what is happening. Big Picture: The Hygiene Hypothesis Allergies and asthma are hypersensitivity’s ◦Observation that there are fewer allergies in tribal populations and children growing up on farms compared to the number of allergies in children in urban settings ◦Possibly due to wider range of microbial exposures in farm setting; also led to lower asthma rates Inflammatory bowel diseases ◦Possible link of lack of normal microbiota metabolic products leading to chronic inflammatory state People that are exposed to more organisms aren’t prone to as much allergies. Growing up in a clean environment your more prone to allergies. Our immune system is educated by our normal flora and early exposure. Kids that are sick early in life and get a lot of antibiotics usually have a lot of allergies and complications due to there immune system was not seeing early on normal flora development. Hypersensitivity Hypersensitivity- is an antigenic response that results in undesirable effects and not normal. It doesn’t really make sense. ◦Example- allergies Hypersensitivity responses occur in individuals who have been sensitized by previous exposure to an antigen (allergen). When a sensitized individual is exposed to that antigen again, the body’s immune system reacts to it in a damaging manner. Four types of hypersensitivity: anaphylactic, cytotoxic, immune complex, delayed cell-mediated ◦These are serious and people can go into anaphylactic shock if not treated immediately because there allergic to something that doesn’t really make sense. ◦Study of hypersensitivity reactions is called immunopathology. Hygiene hypothesis suggests that limiting exposure to pathogens may lower immune tolerance and the ability to cope with harmless antigens. Is better to be exposed to organism early in life so immune system is educated. Table 19-1 Types of Hypersensitivity First 3 all have to due with response to an antibody Type 1 anaphylactic- ige response Type 4 delayed cell hypersensitivity- is only involving our T cells, antibodies don’t have to due with those types of hypersensitivity’s Type 1 1(Anaphylactic) Reactions ◦Type 1 occurs 2 to 30 minutes after a sensitized person is re exposed to an allergen. Serious when the reaction is systemic and it involves the cardiovascular and respiratory system and producing shock and breathing difficulties that are sometimes fatal, or localized, involving limited body regions. Anaphylaxis means the opposite of protected. Antigens combine with IgE antibodies that are attached to mast cells and basophils and these are the cells that are secreting things seen in an inflammatory response. Mast cells and basophils undergo degranulation (The release of contents of secretory granules from mast cells or basophils during anaphylaxis., which releases mediators. Happens when’s IgE antibodies bind to these cells, because mast cells and basophils can bind to the constant region of IgE. ◦Histamine: is stored in the granules and increases blood flow and increases the permeability of blood capillaries resulting in edema (swelling) and erythema (redness). ‣ Other effects include increased mucus secretion (a runny nose, for example) and smooth muscle contraction, which in the respiratory bronchi results in breathing difficulty. ◦Leukotrienes: synthesized by the allergen triggered cell and cause prolonged contraction of smooth muscles. Released which cause contraction of smooth muscle, which can be like asthma attacks. ◦Prostaglandins: synthesized by the allergen triggered cell and affect smooth muscle and increase mucus secretion. ◦These mediators cause the unpleasant and damaging effects of an allergic reaction. These mediators serve as chemotactic agents that, in a few hours, attract neutrophils and eosinophils to the site of the degranulated cell.  The IgE antibodies produced in response to an antigen (such as insect venom or plant pollen) bind by their tails (Fc regions) to Fc receptors on the surfaces of mast cells and basophils, cells of innate immunity Mast cells are especially prevalent in the mucosal and connective tissue of the skin and respiratory tract and in surrounding blood vessels. Basophils in the bloodstream are recruited to the tissues during the allergic response. Localized reactions include common allergic conditions such as hay fever, allergic asthma, and hives (slightly raised, often itchy and reddened areas of the skin). Figure 19-1 The Mechanism of Anaphylaxis IgE can pick up 2 identical antigens and when the IgE molecules are sitting on mast cells and basophils as long as the antigen is in the way there’s no problem, as soon as the antigen attaches to the IgE all of a sudden the receptors start coming together on the surface of the mast cells and the basophils and they’re programmed to degranulate and they start releasing things like leukotrienes and prostaglandins and this causes the inflammatory response. Can have something more localized like hay fever or something more systemic. Type 1 I 1(Anaphylactic) Reactions (2 of 4) Results when release of mediators causes peripheral blood vessels throughout the body to dilate, resulting in a drop in blood pressure (shock) Systemic anaphylaxis (anaphylactic shock)- have all of the blood vessels dilating and complete reduction in blood pressure and having problems breathing due to smooth muscle contracting all due to degranuation. This hypersensitivity is caused by an abnormal release of the factors because you’ve come in contact with something your allergic too. ◦Results when an individual sensitized to an antigen is exposed to it again ◦Involves cardiovascular and respiratory systems causing shock and breathing difficulties or death ◦Allergic mediators cause dilation of peripheral blood vessels resulting in plummeting blood pressure (shock) ◦Injected antigens or bee stings may produce more dramatic responses. Small bee sting can result in shock if not treated right away. ◦Treated with epinephrine which constricts blood vessels and increases blood pressure. Little time to act with this. ◦Other signs and symptoms include narrowing of airway passages, causing respiratory distress, flush or skin rash, tingling sensations, and nausea. Even a small dose of the antigen in question may cause a systemic reaction in someone who is sensitized to it. Type 1 I 1(Anaphylactic) Reactions (3 of 4) Localized anaphylaxis- is things like hay fever and not life threatening ◦Ige is needed for normal immune responses like worm infections which the level of IgE come up in ppl. It creates allergic response which helps break up the worm. In some ppl the IgE creates hyper sensitivity, which can be annoying. ◦Usually associated with limited body regions  ◦Is immediate, temporary, less severe than systemic anaphylaxis. ◦Associated with ingested antigens (food), inhaled antigens (pollen), contact antigens ‣ Pollen, fungal spores, dust mites, animal dander (small flakes of old skin cells from animals), nuts, seafood ◦Symptoms depend on the route of entry ‣ Hay fever: upper respiratory symptoms. In allergies involving the upper respiratory system (such as hay fever), sensitization and production of IgE subsequently involves mast cells that release histamine in the mucous membrane of the upper respiratory tract. ‣ Asthma: affects lower respiratory tract Symptoms such as wheezing and shortness of breath are caused by the constriction of smooth muscles and accumulation of mucus in the bronchial tubes ◦The typical symptoms are itchy and teary eyes, congested nasal passages, coughing, and sneezing ◦Treatment: bronchodilators, leukotriene blockers ◦Proteins in foods can act as antigens and sensitize an individual. There are nine foods that together are responsible for 97% of food allergies: eggs, peanuts, tree-grown nuts, milk, soy, fish, wheat, sesame, and peas. Hives are a characteristic sign of a localized anaphylactic reaction to a food allergen. However, ingestion of food allergens can also trigger systemic anaphylaxis Preventing Anaphylactic Reactions Allergy testing: ◦Antigens are inoculated beneath the epidermis to test for a rapid inflammatory reaction (wheal) that produces redness, swelling, and itching at the inoculation site which is a skin test. Desensitization (or subcutaneous allergen-specific immunotherapy): ◦This procedure consists of increasing dosages of antigen injected beneath the skin. ◦The objective is to cause the production of IgG rather than IgE antibodies, in the hope that the circulating IgG antibodies will act as blocking antibodies to intercept and neutralize the antigens before they can react with cell-bound IgE. ◦Produces IgG, which act as blocking antibodies to intercept and neutralize antigens ◦Desensitization is being used more, you are given the antigen your allergic too and denature it and put in up under neath skin so that the body can see denatured antigen in another format so not breathing it in and its in the skin instead, going to have a response but its going to be an IgG response and the IgG is going to hopefully grab out the pollen before it ever attaches to the IgE, it acts as a blocking antibody, IgG is going to grab the pollen that you breathed in and not let the pollen see the IgG attached to the basophils and mast cells, this is successful. I ◦It’s hoped when they do this when they do this that the T regulatory cells are stimulated a little and suppressing IgE response. Type II2 (Cytotoxic) Reactions We make antibodies to a whole cell. The cells will be lysed. Type II immune reactions are directed against antigens located on cell or tissue surfaces Activation of complement by the combination of I g G or I g M antibodies with an antigenic cell. Generally involve the activation of complement by the combination of IgG or IgM antibodies with an antigenic cell. ◦Causes cell lysis or damage by macrophages. This activation stimulates complement to lyse the affected cell, which might be either a foreign cell or a host cell that carries a foreign antigenic determinant (such as a drug) on its surface ABO blood group system- ◦On our red blood cells there is carbohydrate, A or B, or we don’t have a carbohydrate.  Antibodies form against certain carbohydrate antigens on R B Cs ◦A antigens, B antigens, or both ◦Type O R B Cs: lack both A and B antigens A person’s ABO blood type depends on the presence or absence of carbohydrate antigens located on the cell membranes of red blood cells (RBCs). ABO involves three carbohydrate antigens on the surfaces of cells: A, B, and H. ◦The H gene encodes the H antigen, which is modified by enzymes encoded by the A and B genes, if they are present. Thus a type O person expresses only the H antigen, and type A and B individuals convert the H antigen to the A or B antigens, respectively. Table 19-2 The A B O Blood Group System A- have A carbohydrate B- have B carbohydrate AB- have both carbohydrates O- have nether carbohydrates In ppls plasma (fluid part of they’re blood) they have antibodies to the opposite antigen, so a person who’s type a has anti b antibodies, a person that’s type B has anti A, AB person doesn’t have either, O has both. A type has anti b antibodies because the carb is a repetitive structure so we have anti b antibodies because we’ve seen some pathogen that has the b carbohydrate on it, the person who has a B type blood has seen a pathogen with A carbohydrate. AB- can’t make an antibody to it or else it’ll they have an auto immune disease. Universal recipient. These individuals produce neither anti-A nor anti-B antibodies, so can receive packed cells of the types A, B, AB or O. O- can make antibodies to A or B, they are the universal donor and can donate blood to any type. The cells have neither A nor B antigens that would induce an immune response in a person with type B or A blood, respectively. But the plasma from the type O donor contains antibodies to A and B antigens. If whole blood from a type O donor were given to a type B recipient, the anti-B antibodies in the donor sample would immediately react with the recipient cells, causing agglutination and activating complement, which in turn would cause lysis of the donor’s RBCs as they enter the recipient’s system. The antibody that is made is IgM and theres no class switching so during pregnancy the mother wont reject the baby based on the carb on the babies blood. Type 2 II (Cytotoxic) Reactions (2 of 3) Rh protein is found on RBC. Rh blood group system ◦Rh factor antigen is found on R B Cs of 85% of the population. Majority have it some don’t. ◦blood given to an recipient will stimulate the production of anti-Rh antibodies in the recipient. If blood from an Rh+ donor is given to an Rh- recipient, the donor’s RBCs will stimulate the production of anti-Rh antibodies in the recipient. If the recipient then receives Rh+ red blood cells in a second transfusion, a rapid, serious hemolytic reaction will develop. ◦Hemolytic disease of the newborn (H D N B) ‣ mother with an fetus may produce anti-Rh antibodies if sensitized during pregnancy or birth. If the fetus is Rh+, a mother who is Rh- can become sensitized to the Rh + antigen during pregnancy and birth if fetal RBCs enter her circulation. Her primary antibody response will consist of IgM, which does not cross the placenta. But, the response will also yield memory B cells specific for the Rh factor that have switched to IgG. If the fetus in a second pregnancy is Rh+, those memory B cells will be activated and anti-Rh IgG antibodies will cross the placenta and destroy the fetal RBCs. The fetal body responds to this immune attack by producing large numbers of immature RBCs called erythroblasts. ‣ subsequent antibodies (produced by maternal memory B cells) which damage fetal R B Cs ‣ Prevention: Rho G A M® shots to mother at 28 weeks and shortly after delivery. These are IgM antibodies that cannot cross the placenta and harm the fetus. RhoGAM® is administered via intramuscular or intravenous injection at 28 weeks of pregnancy and soon after delivery. These anti-Rh antibodies combine with any fetal RBCs that have entered the mother’s circulation, reducing the risk of sensitization to the Rh antigen. Basically grab positive baby cells so her immune system doesn’t see it an make an immune response. Figure 19-5 Hemolytic Disease of the Newborn If a women is rh- and the baby is rh+, during the first pregnancy there is no problem, but the mother sees the babies blood and the rh- women will see rh+ blood cells and she will respond and make an immune response to the babies cells problem is if the women has another baby that is rh postive and it will be hemolytic disease of the new born, the mother will see blood of the second baby and since she has memory of it than she would be making an immune response and it an IgG response and this antibody crosses the placenta. Second baby will be attacked by mothers antibodies. Now they give rh- women Rho GAM which is antibody to the rh protein so it will grab babies blood cells she might be exposed to so she doesn’t mount an immune response. Rho GAM shots- grab positive baby cells from her system so she doesn’t make an immune response. Type 3 (Immune Complex) Reactions (1 of 2) Type 3 involve antibodies against soluble antigens circulating in the serum. The antigen–antibody complexes are deposited in organs and cause inflammatory damage. Involves when you have abnormal immune complex that aren’t taken out of circulation through phagocytosis, seen in cases where someone has auto immune disease. Antibodies form against and react with soluble antigens in the serum Form immune complexes only when certain ratios of antigen and antibody occur, they lodge in the basement membranes beneath the cells ◦The antibodies involved are usually IgG ◦A significant excess of antibody leads to the formation of complement-fixing complexes that are rapidly removed from the body by phagocytosis. When there is a significant excess of antigen, soluble complexes form that do not fix complement and do not cause inflammation. ◦However, when a certain antigen–antibody ratio exists, usually with a slight excess of antigen, the soluble complexes that form are small and escape phagocytosis ◦Activate complement, causing inflammation ◦Immune complexes form only when there is a certain ratio of antigen and antibody Figure 19-7 Immune Complex-Mediated Hypersensitivity These complexes circulate in the blood, pass between endothelial cells of the blood vessels, and become trapped in the basement membrane beneath the cells. In this location, they may activate complement and cause a transient inflammatory reaction, attracting neutrophils that release enzymes. Repeated introduction of the same antigen can lead to more serious inflammatory reactions, causing damage to the basement membrane’s endothelial cells within 2 to 8 hours. The complexes start sitting down in vessel lining or kidneys, and the antibodies and antigens when they bind can set up complement cascade and attract macrophages and you start having abnormal immune response in blood vessels or kidneys, this is immune complex, bc your making complexes and not taken out of circulation fast enough because the reaction is to own cells and auto immune reaction. Reaction against ones own cells Type IV4 (Delayed Cell-Mediated) Reactions (1 of 2) Type IV reactions involve cell-mediated immune responses caused by T cells (t helper 1 that help macrophages digest better) ◦Delayed hypersensitivity (delayed cell-mediated reactions)- might take 24 hours to see symptoms and involves T cells. A major factor in the delay is the time required for the participating T cells and macrophages to migrate to and accumulate near the foreign antigens. ‣ Sensitization for delayed hypersensitivity reactions occurs when certain foreign antigens, particularly those that bind to tissue cells, are phagocytized by macrophages, fragmented, and then presented by MHC molecules to antigen receptors on T helper cells.  ‣ Specific binding between the MHC-peptide complex and the Th cell causes the cell to proliferate and develop into memory T cells with the same specificity, as well as cytokine-secreting Th1 cells. Upon initial exposure, and the process of sensitization, no reaction is apparent. On first exposure, antigens are phagocytized and presented to receptors on T cells, causing sensitization ◦No obvious reaction on this exposure Reexposure to antigen causes memory cells to release destructive cytokines Reaction takes a day or more to develop after antigen exposure ◦The delay represents the time for participating T cells and macrophages to migrate and accumulate Transplant rejection is most commonly mediated by cytotoxic T lymphocytes (CTLs), but other mechanisms are by antibody-dependent cell-mediated cytotoxicity or complement-mediated lysis Type IV4 (Delayed Cell-Mediated) Reactions (2 of 2) Delayed cell-mediated hypersensitivity reactions on the skin- ◦Skin test for tuberculosis- if exposed to tuberculosis and you mounted an immune response than you’ll have T cells that will resposne to the mycobacterium tuberculosis, they put protein on skin and in 24 hours if you’ve been expose to tuberculosis and you have memory and T cells resposned, the protein than will wake up memory cells and t helper cells and now macrophages are heading to the site because the T helper cells are secreting factors that attract macrophages and starts inflammatory cascade. ◦There will be swelling, redness, and even pain due to positive reaction to tuberculosis antigen at the site of infection because there is a postive reaction to the tuberculosis antigen. Allergic contact dermatitis- just touching it ◦Haptens combine with proteins in the skin do some people to produce an immune response. Antibodies act as an allergen when its attached to a protein and this is a hapten. ◦Allergic response to poison ivy, cosmetics, metals, and latex are familiar examples of these allergies.. First time exposed to it your fine but you’ve sensitized yourself and memory was created and if you see it again theres a reaction. Figure 19-8 The Development of an Allergy (Allergic Contact Dermatitis) to Catechols from the Poison Ivy Plant First time contact with poison ivy is fine, but second time T helper cells are called from memory and macrophages come in and set up for inflammatory response. Figure- Pentadecacatechol is a mixture of catechols, oils secreted by the plant that dissolve easily in skin oils and penetrate the skin. In the skin, the catechols function as haptens—they combine with skin proteins to become antigenic and provoke an immune response. The first contact with poison ivy sensitizes the susceptible person, and subsequent exposure results in contact dermatitis. The Immune System and Cancer Like an infectious disease, cancer represents a failure of the body’s defenses, including the immune system. Cancer cells arise frequently and are removed by immune surveillane. A cell becomes cancerous when it undergoes transformation and begins to proliferate without control. Cancer cells have tumor-associated antigens that mark them as non self to the immune system. They light themselves up because they have unusual antigens on there surface, sometimes can be fetal antigens we had during fetal development and this is how our CTL’s find them. CTLs, activated macrophages, and N K cells can destroy cancer cells. They find them from the antigens on the surface of the cancer cell. ◦Nk cells can see abberant things on the surface and go to cells and inject them with peferoin or release toxic things and macrophages will start to engulf them to get rid of the cells before they develop into a tumor Limitations in our immune system, maybe our cells don’t see something that lets us see its a cancer cells ◦In some cases there’s no antigenic epitope for the immune system to target ◦Tumor cells reproduce too rapidly, immune system might not keep up with it ◦Some cancerous cells from a metastatic tumor may be transported or reside in a separate location without forming new tumors, in a phenomenon called latent metastasis that allows the cancer to become invisible to the immune system. Tumor becomes invisible to the immune system. Tumor cells secrete factors that inhibit our immune cells, release things so our immune cells can’t get to tumors cells. Figure 19-12 The Interaction between Cytotoxic T Lymphocyte (C T Ls) and Cancer Cells We have cells, NK cells, or CTL that can recognize things on abnormal cancer cell and hopefully destroy before theres is a tumor. Figure- The lymphocytes cause apoptosis (self-destruction) of the cancer cell. Immunotherapy for Cancer Some people recovering from infection had tumor shrinkage because factors like endotoxins in the pathogen cause cells to release TNF by macrophages which shrink tumors Endotoxins from bacteria (Coley’s toxins) stimulate TNF- a that interferes with the blood supply of cancers Vaccines used for prophylaxis (to prevent development of cancers) ◦Cervical, anal, and throat cancer (H P V), liver cancer (hepatitis B). Are part of the recommended child vaccines. Monoclonal antibodies are a promising tool for delivering cancer treatment. Can make a supply of monoclonal antibodies ◦Can treat things like breast cancer and leave our cells alone ◦Mabs may also be used to boost immune response by marking cancer cells as something to attack ◦Combine a Mab with a toxic agent, forming an immunotoxin. An immunotoxin might be used to specifically target and kill cells of a tumor with little damage to healthy cells. ‣ Targets and kills a tumor without damage to healthy cells. Directly targets cancer cells and leaves ours alone. With chemo therapy its toxic to our cells.