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Questions and Answers
What is a common skin manifestation associated with systemic lupus erythematosus (SLE)?
What is a common skin manifestation associated with systemic lupus erythematosus (SLE)?
Which of the following is a major cause of death in patients with SLE?
Which of the following is a major cause of death in patients with SLE?
What type of arthritis is characterized by a nonsuppurative proliferative synovitis?
What type of arthritis is characterized by a nonsuppurative proliferative synovitis?
Which statement about the prevalence of rheumatoid arthritis is true?
Which statement about the prevalence of rheumatoid arthritis is true?
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What is typically used to control acute flare-ups in conditions like SLE?
What is typically used to control acute flare-ups in conditions like SLE?
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What characterizes Type I hypersensitivity reactions?
What characterizes Type I hypersensitivity reactions?
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Which of the following is a prototype disorder of Type I hypersensitivity?
Which of the following is a prototype disorder of Type I hypersensitivity?
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What occurs during the initial response of a localized Type I hypersensitivity reaction?
What occurs during the initial response of a localized Type I hypersensitivity reaction?
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Which of the following symptoms is NOT associated with systemic anaphylaxis?
Which of the following symptoms is NOT associated with systemic anaphylaxis?
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What distinguishes Type II hypersensitivity reactions from other types?
What distinguishes Type II hypersensitivity reactions from other types?
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Type IV hypersensitivity is characterized by which mechanism?
Type IV hypersensitivity is characterized by which mechanism?
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Which cells play a central role in the development of Type I hypersensitivity?
Which cells play a central role in the development of Type I hypersensitivity?
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What is a common consequence of systemic anaphylaxis if immediate intervention is not taken?
What is a common consequence of systemic anaphylaxis if immediate intervention is not taken?
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What is a potential consequence of anaphylactic shock?
What is a potential consequence of anaphylactic shock?
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Which of the following is a common form of localized anaphylactic reaction?
Which of the following is a common form of localized anaphylactic reaction?
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What role do IgE antibodies play in hypersensitivity reactions?
What role do IgE antibodies play in hypersensitivity reactions?
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What triggers airway hyperresponsiveness in asthma patients?
What triggers airway hyperresponsiveness in asthma patients?
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What is a definitive characteristic of type II hypersensitivity?
What is a definitive characteristic of type II hypersensitivity?
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What is a characteristic of mucous plugs associated with asthma?
What is a characteristic of mucous plugs associated with asthma?
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What condition arises due to rhesus antigen incompatibility between mother and fetus?
What condition arises due to rhesus antigen incompatibility between mother and fetus?
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How do antibodies contribute to autoimmune conditions in type II hypersensitivity?
How do antibodies contribute to autoimmune conditions in type II hypersensitivity?
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What is the primary function of B lymphocytes in the immune system?
What is the primary function of B lymphocytes in the immune system?
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Which immunoglobulin is known for its role in mucosal immunity?
Which immunoglobulin is known for its role in mucosal immunity?
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What type of immunity is primarily mediated by T lymphocytes?
What type of immunity is primarily mediated by T lymphocytes?
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Which cell type is responsible for phagocytizing and killing microbes in humoral immunity?
Which cell type is responsible for phagocytizing and killing microbes in humoral immunity?
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Which immunoglobulin is responsible for triggering allergic reactions and protecting against parasitic worms?
Which immunoglobulin is responsible for triggering allergic reactions and protecting against parasitic worms?
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What role do helper T cells play in cellular immunity?
What role do helper T cells play in cellular immunity?
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What is a distinguishing feature of natural killer (NK) cells?
What is a distinguishing feature of natural killer (NK) cells?
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Which cells assist both humoral immunity and cellular immunity?
Which cells assist both humoral immunity and cellular immunity?
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Which immunoglobulin is secreted in the early stages of immune response?
Which immunoglobulin is secreted in the early stages of immune response?
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What is the end product of humoral immunity?
What is the end product of humoral immunity?
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Which of the following routes does not contribute to mother-to-infant transmission of HIV?
Which of the following routes does not contribute to mother-to-infant transmission of HIV?
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What characterizes the acute phase of HIV infection?
What characterizes the acute phase of HIV infection?
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Which of the following statements is true regarding the chronic phase of HIV infection?
Which of the following statements is true regarding the chronic phase of HIV infection?
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Amyloidosis is characterized by the deposition of which type of protein?
Amyloidosis is characterized by the deposition of which type of protein?
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What is a key feature of the crisis phase of HIV infection?
What is a key feature of the crisis phase of HIV infection?
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How can amyloid be detected in biopsy specimens?
How can amyloid be detected in biopsy specimens?
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What is NOT a potential outcome in the crisis phase of HIV infection?
What is NOT a potential outcome in the crisis phase of HIV infection?
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Which statement accurately describes the natural history of HIV infection?
Which statement accurately describes the natural history of HIV infection?
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Study Notes
Cells and Tissues of the Immune System
- B lymphocytes participate in immunity by directly neutralizing extracellular microbes, by activating complement, or by activating effector cells like neutrophils and macrophages which then kill microorganisms
- B lymphocytes make up 10% to 20% of the circulating peripheral lymphocyte population
- B lymphocytes can be found in bone marrow, peripheral lymphoid tissues (lymph nodes, spleen, tonsils, and the gastrointestinal tract)
- B lymphocytes are stimulated to form plasma cells which then secrete immunoglobulins, the mediators of humoral immunity
- The five basic immunoglobulin isotypes are IgG, IgM, IgA, IgD, and IgE
- IgG, IgM, and IgA make up more than 95% of circulating antibodies
- IgA is an important mediator of mucosal immunity
- IgE is important for helminth infections
- T lymphocytes (T cells) can either directly lyse targets by cytotoxic T cells, or produce soluble protein mediators called cytokines (made by Helper T cells) to orchestrate the antimicrobial immune response
- T lymphocytes make up 60% to 70% of lymphocytes found in circulating blood
- T lymphocytes can be found in the splenic periarteriolar sheaths and lymph node interfollicular zones
- Macrophages phagocytize and kill microbes coated by antibodies and/or complement
- Macrophages are important effectors of humoral immunity
- Macrophages produce cytokines
- Dendritic cells are cells with dendritic morphology (with fine dendritic cytoplasmic processes) that occur as one of two types: Interdigitating dendritic cells and follicular dendritic cells
- Interdigitating dendritic cells occur in lymphoid tissues, the interstitium of the heart, and the lungs
- Follicular dendritic cells are located in the germinal centers of lymphoid follicles in the spleen and lymph nodes
- Natural killer (NK) cells comprise 10% to 15% of peripheral blood lymphocytes
- NK cells contain azurophilic granules and are able to lyse a variety of tumor cells, virally infected cells, and some normal cells
Humoral vs. Cellular Immunity
- The principal cell in humoral immunity is the B lymphocyte
- The principal cell in cellular immunity is the T lymphocyte
- Humoral immunity relies on macrophages for assistance
- Cellular immunity relies on macrophages and T helper cells for assistance
- The end result of humoral immunity is immunoglobulin
- The end result of cellular immunity is lymphokines and cytotoxic cells
- Humoral immunity is effective against bacteria and toxins
- Cellular immunity is effective against viruses, fungi, transplants, and tumor cells
Hypersensitivity Reactions
- Hypersensitivity reactions are abnormal or excessive sensitivities to an antigen
- Hypersensitivity reactions are classified based on the immunologic mechanism that initiates the disease
- Type I hypersensitivity arises from IgE antibodies adsorbed on mast cells or basophils
- Type II hypersensitivity is caused by humoral antibodies that bind to fixed tissue or cell surface antigens
- Type III hypersensitivity is called “immune complex disease” and occurs when antibodies bind antigens to form large antigen-antibody complexes that precipitate in various vascular beds
- Type IV hypersensitivity is also called “delayed-type hypersensitivity” and are cell-mediated immune responses where antigen-specific T lymphocytes are the ultimate cause of the damage
Type I Hypersensitivity
- Type I hypersensitivity, also known as allergy or anaphylaxis, is a rapid tissue response occurring within minutes due to the interaction of an allergen and IgE antibody bound to mast cells or basophils in a sensitized host
- Two well-defined phases of localized type I reactions are the initial response and the late-phase reaction
- The initial response to Type I hypersensitivity is characterized by vasodilation, vascular leakage, and smooth muscle spasm that usually develops within 5 to 30 minutes after exposure to an allergen and subsides within 60 minutes
- The late-phase reaction to Type I hypersensitivity sets in 2 to 8 hours later and lasts for several days
- Mast cells and basophils are central to the development of Type I hypersensitivity
- Systemic anaphylaxis results from systemic (parenteral) administration of protein antigens or drugs (e.g. bee venom or penicillin)
- Anaphylaxis can present with itching, urticaria, skin erythema, respiratory difficulty (caused by pulmonary bronchoconstriction), upper airway obstruction caused by laryngeal edema, vomiting, abdominal cramps, diarrhea, anaphylactic shock, circulatory collapse and death
- Localized Type I hypersensitivity reactions occur when the antigen is confined to a particular site due to the route of exposure: skin (contact, causing urticaria), GIT (ingestiion, causing diarrhea), Lung (inhalation, causing bronchoconstriction)
- Common forms of skin and food allergies, hay fever and asthma are examples of localized anaphylactic reactions
- Atopy is used to imply a familial predisposition to localized type I reactions
- Type I hypersensitivity plays an important role in parasitic infections
- IgE antibodies are produced in response to many helminthic infections
Type II Hypersensitivity (Antibody Dependent)
- Type II hypersensitivity is mediated by antibodies directed against target antigens on the surface of cells or other tissue components
- The antigens in Type II hypersensitivity can be normal molecules intrinsic to cell membranes or extracellular matrices
- Type II hypersensitivity can occur during situations like: transfusion reactions, erythroblastosis fetalis due to rhesus antigen incompatibility, autoimmune hemolytic anemia, agranulocytosis, thrombocytopenia, drug reactions, certain hematological and immunological disorders
- In transfusion reactions, red cells from an incompatible donor are destroyed after being coated with recipient antibodies directed against donor blood group antigens
- In erythroblastosis fetalis, antibodies generated by the mother against fetal red cell antigens cross the placenta and destroy fetal red blood cells
- Autoimmune hemolytic anemia, agranulocytosis, or thrombocytopenia occur when an individual generates antibodies against their own blood cells
- In drug reactions, antibodies are directed against a particular drug that has nonspecifically adsorbed to a cell surface
Lupus Erythematosus
- Lupus erythematosus (SLE) is an autoimmune disorder where immune complexes deposit within various tissues
- SLE has a wide range of manifestations with diverse and often nonspecific symptoms that can affect any part of the body
- The symptoms of SLE can wax and wane, making diagnosis difficult
- SLE has a variable course and can range from mild skin manifestations to severe multi-system involvement
- SLE is characterized by remissions and relapses that span years to decades
- SLE can be fatal, but with current therapies 90% 5-year and 80% 10-year survival can be expected
Rheumatoid Arthritis
- Rheumatoid arthritis is a systemic, chronic inflammatory disease that affects multiple tissues, primarily attacking joints, causing a nonsuppurative proliferative synovitis that frequently progresses to destroy articular cartilage and underlying bone with resulting disabling arthritis
- Destroyed articular cartilage is replaced by chronic inflammatory pannus
- Rheumatoid arthritis has a prevalence of approximately 1%
- Rheumatoid arthritis is 3-5 times more common in women than in men
- The peak incidence of rheumatoid arthritis occurs in adults 20-40 years old
- Though there is a genetic predisposition to rheumatoid arthritis, the cause or causes of the disease remain unknown
HIV Infection
- HIV (Human Immunodeficiency Virus) is a retrovirus that is responsible for AIDS (Acquired Immunodeficiency Syndrome)
- HIV has two major targets: the immune system and the central nervous system
- There are three phases to HIV Infection: an early, acute phase, a middle, chronic phase, and a final crisis phase
- The acute phase of HIV infection is a self-limited illness that develops in 50% to 70% of adults 3 to 6 weeks after infection
- The acute phase of HIV infection is characterized by nonspecific symptoms like sore throat, myalgia, fever, rash, and sometimes aseptic meningitis
- The acute phase of HIV infection is also characterized by high levels of virus production, viremia, and widespread seeding of the peripheral lymphoid tissues
- The chronic phase of HIV infection represents a stage where the virus is relatively contained
- During the chronic phase of HIV infection the immune system is intact, but HIV continues to replicate for several years
- During the chronic phase of HIV infection, patients may be asymptomatic or develop persistent lymphadenopathy
- The crisis phase of HIV infection is characterized by a catastrophic breakdown of host defenses, a marked increase in viremia, and clinical disease
- Patients in the crisis phase of HIV infection present with fever of more than 1 month’s duration, fatigue, weight loss, and diarrhea
- After a variable interval, patients in the crisis phase of HIV infection will develop serious opportunistic infections, secondary neoplasms and/or neurologic manifestations and are said to have developed full-blown AIDS
- Mother-to-infant transmission (vertical transmission) is the major cause of pediatric AIDS
- The three routes for mother-to-infant transmission include: in utero, transplacental spread, intrapartum during delivery, and ingestion of HIV-contaminated milk
- HIV infection cannot be transmitted by casual personal contact in the home, workplace, or school, and there is no convincing evidence for spread by insect bites
Amyloidosis
- Amyloidosis is characterized by the deposition of an abnormal extracellular fibrillar protein (amyloid) in many tissues
- Amyloid is derived from many different precursor peptides
- Amyloid is deposited in the form of a meshwork of rigid, straight fibrils
- Amyloid fibrils are 10-15 nm in diameter and have a beta-pleated configuration
- Amyloid can be recognized by light microscopy in biopsy specimens
- Amyloid is detected by the Congo Red test giving an orange color
- Other stains used to identify amyloid include: Sirius red, methyl violet, and Iodine
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Description
Explore the vital roles of B and T lymphocytes in immunity with this quiz. Understand how B lymphocytes neutralize microbes, secrete antibodies, and how T cells respond to infections. Test your knowledge on immunoglobulin isotypes and the mechanics of the immune response.
