Immunity and Infections in Medicine

Acquired Immunity

• An individual develops naturally acquired active immunity through exposure to organisms that cause a disease.
• This type of immunity is not obtained through immunization with antibodies or administration of a vaccine.

Spleen Function and Removal

• The spleen plays a vital role in the body, and its removal may lead to health problems.
• The liver can take over some of the spleen's functions, but not all.
• The best response to a patient's question about spleen removal is to acknowledge the potential risks and explain the liver's role in compensation.

Nonspecific Body Defenses

• Enzymes in body fluids can destroy pathogens through chemical barriers.
• Inflammation is a nonspecific body defense that involves the movement of neutrophils and monocytes from the bloodstream to attack pathogens in other tissues.
• Phagocytosis is a type of nonspecific body defense that involves the engulfing and destruction of pathogens by cells such as neutrophils and monocytes.

Interferon and Nonspecific Body Defenses

• Interferon in the blood acts as a chemical barrier, providing a nonspecific defense against pathogens.
• Interferon is not a mechanical barrier, fever, inflammation, or phagocytosis.

Nonspecific Body Defenses

• In response to an injury, inflammation occurs.
• Mechanical barriers, such as mucous membranes and skin, provide a physical defense against pathogens.
• Inflammation is a nonspecific defense that activates cells in the body to attack pathogens.
• During inflammation, blood vessels dilate, bringing more blood to the area, which in turn brings:
  • Phagocytic white blood cells to attack the pathogen.
  • Proteins to replace injured tissues.
  • Clotting factors to stop any bleeding.

Lymphocytes

• Most lymphocytes in the blood are B cells.
• B cells become plasma cells in response to an antigen and make antibodies against the specific antigen.
• T cells are a type of lymphocyte, but they do not produce antibodies.
• Natural killer (NK) cells are a type of lymphocyte that do not respond to specific antigens.

Immune Response Mechanisms

• Macrophages and lymphocytes are involved in specific defenses against pathogens.
• T cells are responsible for binding to antigens on cells and attacking them directly.

Cell Functions

• B cells produce antibodies that target specific antigens.
• Natural killer (NK) cells target and destroy cancer cells and virally infected cells.
• T cells produce memory cells that trigger a strong response to future exposures to the same antigen.

Signaling and Activation

• Monokines increase B cell production and stimulate red bone marrow to produce more WBCs.
• T cells secrete lymphokines, which are signaling molecules that activate immune responses.

Cytokines and Immune Response

• Cytokines are signaling molecules that facilitate communication between immune cells.
• Haptens are small molecules that can elicit an immune response when attached to a carrier protein.

Key Players in Immune Response

• Macrophages and lymphocytes work together to provide specific defenses against pathogens.
• Natural killer (NK) cells are key players in targeting cancer cells.

Immune System Components

• Major histocompatibility complex (MHC) is unique to an individual, present on every cell in that person's body, and activates T cells.

Cell Functions

• Natural killer (NK) cells secrete chemicals that produce holes in the membranes of harmful cells, and do not require recognition of a specific antigen to start destroying pathogens.

Activated T Cells

Cytotoxic T Cells

• Active against viruses and protects the body against cancer.

Helper T Cells

• Increase phagocytosis and antibody formation.

Memory T Cells

• Prevent a person from having the same disease twice.

Immunoglobulins and their Functions

• IgA primarily binds to antigens on food, bacteria, or incompatible blood cells.
• IgA is found in secretions of the body and prevents pathogens from entering the body.
• IgM recognizes bacteria, viruses, and toxins.
• IgE triggers an allergic reaction.
• IgD is thought to control the activity of B cells.

Secondary Immune Response

• A secondary immune response is very rapid.
• It causes memory cells to develop.
• It is carried out by memory cells.
• It requires re-exposure to an antigen.
• It does not prevent a person from developing a disease from the antigen.

Immune Responses

• Primary immune response: takes several weeks, describes the initial response to an antigen.

Types of Immunity

• Naturally acquired active immunity: results from exposure to an antigen, such as having an infectious disease.
• Naturally acquired passive immunity: crosses the placenta and passes through breast milk.
• Artificially acquired active immunity: results from vaccination or immunization.
• Artificially acquired passive immunity: requires injection with an antibody.
• Species resistance: type of immunity that results simply from being human, as opposed to being another species.

Note: These study notes focus on the key concepts and facts, avoiding repetition and providing context for each type of immunity.

Immunity and Vaccines

• Artificially acquired active immunity results from a vaccine.

Allergy Treatment

• Antihistamines are over-the-counter medications that can effectively treat allergies.

Allergies and Immune Response

• Allergy is an excessive immune response that involves IgE antibodies.
• Anaphylaxis is a life-threatening event that causes a rapid drop in blood pressure.

Anaphylaxis Treatment

• Epinephrine is used to rescue a person experiencing anaphylaxis.

Cancer Diagnosis

• Staging is the process that identifies how far cancer cells have spread.

Breast Cancer Diagnosis

• Elisa is diagnosed with stage II breast cancer, which means the cancer has not spread beyond the breast.
• The medical assistant should respond to Elisa's concern by saying: "All cancers are potentially serious, but your cancer has not spread beyond the breast."

Carcinogens and Cancer

• A carcinogen is a factor that causes the formation of cancer.

Systemic Lupus Erythematosus (SLE)

• SLE is characterized by symptoms including:
  • "Butterfly" rash
  • Tender lymph nodes in the neck
  • Renal failure
• Headaches are not a symptom of SLE.

Chronic Fatigue Syndrome

• Symptoms of chronic fatigue syndrome include:
  • Joint pain
  • Tender lymph nodes
  • Fever (not listed as an option)
• Numbness of fingers and toes is not a symptom of chronic fatigue syndrome.

Lymphatic System

• The contraction of skeletal muscles causes lymph to flow through the lymphatic vessels.
• If lymph cannot be pushed through the vessels, edema develops.

Spleen Function

• Removes aged RBCs from circulation
• Located in the abdomen, not in the thorax above the heart
• Does not produce T-lymphocytes
• Does not produce thymosin
• Does not decrease in size as a person ages

Thymus Function

• Decreases in size as a person ages
• Produces T-lymphocytes
• Not the largest lymphatic organ
• Not filled with blood and macrophages
• If removed, the liver does not take over its functions

Immune System Disorders

• AIDS (Acquired Immune Deficiency Syndrome) is a possible diagnosis for a patient with a low T-cell count, high temperature, and low blood pressure
• Systemic lupus erythematosus, chronic fatigue syndrome, lymphedema, and mononucleosis are other possible diagnoses to rule out

Mononucleosis

• Can be spread through contact with saliva, not just kissing
• Precautions to take when working with a patient suspected to have mononucleosis include wearing a mask while in the exam room and using full PPE (personal protective equipment)

Patient's Condition

• Ted experiences weakness and significant weight loss recently.
• His blood tests reveal a low T-cell count of 178.

Vital Signs

• His temperature is elevated at 102.4°F.
• His blood pressure is 100/62 mmHg.

Potential Diagnosis

• The practitioner may investigate further to rule out AIDS based on Ted's symptoms.

Immunity and Immune System

• Naturally acquired active immunity develops from exposure to an antigen, such as getting a disease and then becoming immune to it.
• Artificially acquired active immunity results from a vaccine, which introduces a weakened or killed pathogen to the body, triggering an immune response.
• Naturally acquired passive immunity occurs when antibodies are passed from mother to fetus during pregnancy or through breast milk.
• Artificially acquired passive immunity results from injection with an antibody, providing immediate but temporary protection.

Immune Response

• Primary immune response: The first exposure to an antigen, which triggers an immune response, but takes time to develop.
• Secondary immune response: A rapid and strong response to a second exposure to the same antigen, carried out by memory cells.

Types of Immunity

• Species resistance: A natural defense against certain diseases, unique to a species.
• Naturally acquired active immunity: Results from exposure to an antigen.
• Artificially acquired active immunity: Results from a vaccine.
• Naturally acquired passive immunity: Results from antibodies passed from mother to fetus or through breast milk.
• Artificially acquired passive immunity: Results from injection with an antibody.

Immune System Cells

• B cells: Produce antibodies against specific antigens.
• T cells: Directly attack infected cells or produce chemical signals that activate other immune responses.
• Natural killer (NK) cells: Attack cancer cells and cells infected with viruses.
• Macrophages: Engulf and digest foreign substances and cellular debris.
• Lymphocytes: Produce antibodies or directly attack infected cells.

Immune System Functions

• Phagocytosis: Engulfment and digestion of foreign substances and cellular debris.
• Inflammation: A response to tissue damage, characterized by increased blood flow, swelling, and pain.
• Fever: A response to infection, causing body temperature to rise.

Immune System Organs

• Spleen: Removes aged red blood cells from circulation and stores platelets and white blood cells.
• Thymus: Produces thymosin, which aids in T-cell development.
• Lymph nodes: Filter lymph fluid and trap pathogens and cellular waste.

Immune System Disorders

• Allergy: An excessive immune response to a harmless substance, involving IgE antibodies.
• Anaphylaxis: A severe, life-threatening allergic reaction, characterized by a rapid drop in blood pressure.
• Autoimmune disorders: The immune system attacks healthy cells and tissues, such as in lupus or rheumatoid arthritis.
• Immunodeficiency disorders: The immune system is weakened, making it difficult to fight infections, as in AIDS.

Cancer

• Carcinogen: Any factor that causes the formation of cancer.
• Staging: A system to describe the extent of cancer spread.

Lymphatic System

• Lymphatic vessels: Transport lymph fluid, which contains immune cells and proteins.
• Lymph nodes: Filter lymph fluid and trap pathogens and cellular waste.
• Skeletal muscles: Help to push lymph through vessels by contracting and relaxing.

Phagocytic Cells

• Large phagocytic cells that produce monokines and digest pathogens in the lymph are macrophages.
• Neutrophils and macrophages are the most active phagocytes in the blood.
• Macrophages are a type of white blood cell that engulf and destroy pathogens and unwanted debris in the body.

Autoimmune Diseases

• In an autoimmune disease, the body begins to attack its own antigens.

Serum Proteins

• Major proteins in serum that attack pathogens and can also attract macrophages to pathogens and stimulate inflammation are called antibodies.

T Cell Response

• T cells respond to antigens by secreting cytokines that increase T cell production and directly kill cells that have antigens.

Tears and Immune Defense

• Lysozymes act as a chemical barrier and destroy pathogens on the surface of the eye in tears.

Cytokines and Immune Response

• Cytokines known as interleukins assist in regulation of the immune response by increasing B cell production and stimulating red bone marrow to produce more white blood cells.

Infectious Diseases

• Mononucleosis is a highly contagious viral infection spread through the saliva of the infected person and frequently affects teenagers.

Nonspecific Body Defense

• Diapedesis is the nonspecific body defense mechanism in which monocytes leave the bloodstream and become macrophages to attack pathogens in other tissues.

Allergy and Immune Response

• A substance that triggers an allergic response is called an allergen.
• When an area of the body becomes injured or infected with a pathogen, inflammation can result, causing blood vessels in the injured area to dilate and become leaky.
• The presence of a pathogen in or on the body is known as an infection.
• A foreign substance in the body is called an antigen.
• Lymphocytes known as cytotoxic cells primarily target cancer cells, killing these harmful cells on contact by secreting chemicals that produce holes in the membranes, causing them to burst.

Digestive System Disorders

• Celiac disease is an immune reaction linked to eating gluten that triggers a reaction causing the body to attack the small intestinal mucosa.

Lymphoid Tissue

• Masses of lymphoid tissue not surrounded by a capsule that are distributed in the connective tissue of mucosa are known as lymphoid tissue.

Palate Function

• The palate's main function is to separate oral and nasal cavities during swallowing.

Enzymes in Saliva

• Saliva contains the enzyme amylase, which breaks down carbohydrates.

Epiglottis Function

• The main function of the epiglottis is to cover the opening of the larynx during swallowing.

Gluten-Related Disorder

• Celiac disease is an immune reaction linked to eating gluten that triggers a reaction causing the body to attack the small intestinal mucosa.

Lymphoid Tissue

• Masses of lymphoid tissue not surrounded by a capsule that are distributed in the connective tissue of mucosa are known as lymphoid tissue.
• Lymphoid tissue is not the same as lymphocytes, macrophages, lymph nodes, thymus, or spleen.