Chapter 45: The Immune System

1.

Question: What is Immunology? Answer: study of the immune system, immune response, molecular mechanisms that help defend against microbial attacks or other foreign antigens.

2.

Question: What is the definition of immune response? Answer: Collective and coordinated response to the introduction of foreign substances.

3.

Question: What is the immune system? Answer: A system of cells, tissues, and their soluble products.

4.

Question: Define antigen, epitope, and paratope. Answer: An antigen is any foreign molecule that triggers an adaptive immune response.

5.

Question: Define epitope. Answer: The small specific part of the antigen that the antibody molecules bind to is called an antigenic determinant or an epitope.

6.

Question: Define paratope. Answer: The corresponding site on the antibody that binds to an epitope is called a paratope.

7.

Question: What are the three ways antibody-bound antigens are processed to protect the host from infection? Answer: a. Neutralization. b. Opsonization. c. Complement activation.

8.

Question: Describe the structure of antibody and T-Cell receptor. Answer: Understand the different polypeptide chains in antibody and TCRs as.

9.

Question: What are the five classes (Isotypes) of antibodies? Answer: IgM, IgG, IgD, IgA, and IgE.

10.

Question: How is IgM secreted? Answer: IgM is secreted as a pentamer of immunoglobulin monomers.

11.

Question: What is the role of IgD? Answer: IgD occurs with IgM as a receptor on the surfaces of B cells, its function is uncertain.

12.

Question: What is the function of IgE related to mast cells and basophils? Answer: IgE secreted by plasma cells of the skin and linings of the gastrointestinal and respiratory tract binds to basophils and mast cells, triggering release of histamine.

13.

Question: How is IgA secreted? Answer: IgA is secreted as a dimer.

14.

Question: What is IgG? Answer: IgG(γ) is the most abundant antibody circulating in the blood and lymphatic system – produced in large amounts when the body is exposed a second time to the same antigen.

15.

Question: What stimuli produce IgE antibodies? Answer: IgE antibodies are produced in response to parasites and, in genetically susceptible individuals, to otherwise harmless environmental antigens (allergens), such as pollen, foods, and drugs.

16.

Question: What are the steps of antibody-mediated immunity? Answer: Refer to lecture slides for detailed explanation for each step.

17.

Question: What is Passive immunity? Answer: Acquisition of antibodies from another person – including antibodies passed from mother to child through the placenta or in breast milk.

18.

Question: How are antibodies used in research? Answer: a. Immunohistochemistry techniques – ELISA, Immunoblotting. b. Monoclonal antibody production – Hybridoma technology.

19.

Question: What constitutes immune system malfunctioning? Answer: a. Allergies and hypersensitivity. b. Autoimmune disorders.

20.

Question: What are the steps of cell-mediated immunity? Answer: A. Presentation of antigens on cell surface. Viral proteins are degraded into fragments that act as antigens. The antigens are displayed on the cell surface bound to class I MHC proteins, making.

21.

Question: What happens to infected cells in cell-mediated immunity? Answer: apoptosis and die.

22.

Question: What is the difference between immunoglobulins and antibodies? Answer: Immunoglobulins are cell surface bound, whereas antibodies are secreted by plasma B cells.

23.

Question: What are immunoglobulin domain-like molecules? Answer: A large class of molecules including antibodies, sharing similar protein folding domains.

24.

Question: What activates a naive B cell? Answer: Binding to a foreign antigen.

25.

Question: What is the function of a plasma B cell? Answer: Secretes antibodies.

26.

Question: Describe the basic structure of an antibody molecule. Answer: Two identical heavy chains and two identical light chains.

27.

Question: What are the main regions of heavy and light chains? Answer: Variable region and constant region.

28.

Question: What is the function of the variable region? Answer: Contains the antigen binding site, contributes to high specificity.

29.

Question: What is the function of the constant region? Answer: In membrane-bound immunoglobulins (BCRs), it contains the transmembrane domain that anchors to the plasma membrane. Determines antibody isotype.

30.

Question: Are antibodies soluble or membrane-bound? Answer: Antibodies are soluble, lacking the membrane anchoring domain.

31.

Question: What are epitopes? Answer: Small, specific parts of antigens that antibodies bind to.

32.

Question: What kind of chemical structures can epitopes have? Answer: Diverse, including carbohydrate residues, amino acid residues, toxin molecules.

33.

Question: How do T-cell receptors recognize antigens? Answer: They bind to peptides that are processed by antigen-presenting cells (APCs) and presented in the context of MHC molecules.

34.

Question: What are professional antigen presenting cells (APCs)? Answer: Cells that process and present antigens to T cells, including dendritic cells, macrophages, and B cells.

35.

Question: What are MHC molecules? Answer: Major Histocompatibility Complex molecules, self-identifying proteins on cell surfaces. T cells recognize antigens only in the presence of MHC.

36.

Question: What are the five major isotypes of immunoglobulin molecules? Answer: IgG, IgM, IgD, IgA, IgE.

37.

Question: What determines the isotype of an immunoglobulin? Answer: Differences in the heavy chain constant region.

38.

Question: What are the Greek letters for the heavy chains of each isotype? Answer: Gamma (γ) for IgG, Mu (μ) for IgM, Delta (δ) for IgD, Alpha (α) for IgA, Epsilon (ε) for IgE.

39.

Question: What are the light chain isotypes (classes)? Answer: Kappa (κ) and Lambda (λ) chains.

40.

Question: Is there a functional difference between Kappa and Lambda light chains? Answer: No functional difference found.

41.

Question: In humans, what is the proportion of antibody molecules carrying Kappa vs Lambda chains? Answer: Two-thirds carry Kappa, one-third carry Lambda.

42.

Question: What structural differences exist between antibody isotypes? Answer: Differences in heavy chain C region length, disulfide bond locations, hinge regions, and glycosylation.

43.

Question: Which isotypes have a hinge region? Answer: IgG, IgA, IgD.

44.

Question: Which isotypes lack a hinge region? Answer: IgM, IgE.

45.

Question: How do secreted IgD, IgE, and IgG exist? Answer: Always as monomers.

46.

Question: How does secreted IgA exist? Answer: Forms monomers and dimers.

47.

Question: How does secreted IgM exist? Answer: Forms only pentamers.

48.

Question: What joins the antibody molecules in IgA dimers and IgM pentamers? Answer: A joining chain or J chain.

49.

Question: What antibody isotypes are antigen receptors on circulating B cells? Answer: IgM and IgD.

50.

Question: What is the first antibody class secreted in any immune response? Answer: IgM.

51.

Question: What are the main antibodies found in blood, lymph, and connective tissues? Answer: IgM, IgA, and IgG.

52.

Question: Which immunoglobulin isotypes provide bulk of specific adaptive immunity against bacteria and viruses in ECF? Answer: IgM and IgG.

53.

Question: Where is secreted IgA found? Answer: Lining GI, respiratory, GU tracts, in tears, saliva, breast milk.

54.

Question: What is the function of IgA in saliva? Answer: Keeps the mouth free of pathogens.

55.

Question: What kind of immunity does IgA in mother's milk provide? Answer: Passive immunity to babies.

56.

Question: What is IgE important for? Answer: Responding to parasites and mediating allergic responses.

57.

Question: How does IgE mediate allergic responses? Answer: Binds receptors on mast cells and basophils, sensitizing them to allergens and triggering histamine release.

58.

Question: What is the function of IgD? Answer: Occurs with IgM on B cell surface, may be important for B cell activation; exact role is still unclear.

59.

Question: What is somatic gene recombination (or rearrangement)? Answer: A process where DNA segments encoding antibody (and TCR) regions are recombined in different ways to generate diversity. Occurs in somatic cells (lymphocytes) during maturation.

60.

Question: What is VDJ recombination? Answer: The basic process of somatic recombination that generates antibody and T cell receptor diversity. Involves V, D, J gene segments for heavy chains and V, J segments for light chains.

61.

Question: Who discovered the process of VDJ recombination? Answer: Susumu Tonegawa, awarded the 1987 Nobel Prize in Physiology or Medicine.

62.

Question: What enzyme catalyzes VDJ recombination? Answer: VDJ recombinase.

63.

Question: VDJ recombination process (Heavy chain)? Answer: First, a D segment joins a J segment (DJ recombination). Second, a V segment joins the combined DJ segment (V-DJ recombination).

64.

Question: VDJ recombination process (Light chain)? Answer: A V segment joins a J segment (VJ recombination); no D segment is involved.

65.

Question: Number of combinations for Kappa light chain VJ recombination? Answer: Approx. 40 Vκ segments and 5 Jκ segments recombine in ~200 ways.

66.

Question: Number of combinations for Lambda light chain VJ recombination? Answer: Approx. 30 Vλ segments and 4 Jλ segments recombine in ~120 ways.

67.

Question: Number of combinations for Heavy chain VDJ recombination? Answer: Approx. 65 VH, 27 D, and 6 JH segments can produce 10,530 combinations.

68.

Question: Light Chain Gene Rearrangement and Expression Process? Answer: Random V and J segments recombine. The VJ segment recombines with the C segment. DNA is transcribed to pre-mRNA. RNA processing (splicing, etc.) produces mature mRNA. mRNA is translated to the light chain polypeptide.

69.

Question: Antigen Presentation Process? Answer: APC engulfs pathogen/antigen. Antigen is degraded into peptides. Peptides bind to MHC molecule (Class I or II). Peptide-MHC complex moves to cell surface and is displayed.

70.

Question: What is MHC Class I? Answer: MHC molecules that present peptides from intracellular pathogens to cytotoxic T cells (CD8+). Found on most nucleated cells.

71.

Question: What is MHC Class II? Answer: MHC molecules that present peptides from extracellular pathogens to helper T cells (CD4+). Found on professional APCs.

72.

Question: What are CD4+ T cells? Answer: Helper T cells, recognize antigens presented by MHC Class II, activate macrophages and B cells.

73.

Question: What are CD8+ T cells? Answer: Cytotoxic T cells, recognize antigens presented by MHC Class I, kill infected cells.

74.

Question: What happens during a primary immune response? Answer: First exposure to antigen. Naive lymphocytes activated. Clonal expansion. Differentiation into plasma cells and memory cells. Antibodies appear in blood in 3-14 days. Response ends by week 4.

75.

Question: What happens during a secondary immune response? Answer: Second exposure to the same antigen. Rapid activation of memory cells. Faster and stronger response than primary. Less antigen needed. Many more antibodies produced.

76.

Question: What is Immunological Memory? Answer: The adaptive immune system remembers prior exposure to an antigen, allowing for a faster and stronger response upon re-exposure.

77.

Question: What is Active Immunity? Answer: Immunity acquired by exposing an individual to antigens, generating an adaptive immune response and immunological memory.

78.

Question: What is Passive Immunity? Answer: Acquisition of antibodies from another person or animal (e.g., maternal antibodies, antitoxins). It is short-lived and produces no memory.

79.

Question: What is the complement system? Answer: A group of blood proteins that aid the innate immune response, can be activated by antibodies, form membrane attack complexes (MAC) to lyse cells.

80.

Question: Complement Activation Process leading to lysis? Answer: Complement proteins activated (e.g., by antibody binding). Subunits assemble on pathogen surface. Form pores (MAC) in membrane. Cell lysis and death.

81.

Question: How do antibodies neutralize pathogens? Answer: By binding to them, inhibiting their toxic effects or infectivity.

82.

Question: How do antibodies opsonize pathogens? Answer: By coating pathogens, making them easier for phagocytic cells to ingest and kill.

83.

Question: What are the two types of adaptive immune responses? Answer: Humoral immunity and Cell-mediated immunity.

84.

Question: What is Humoral Immunity mediated by? Answer: B lymphocytes secreting antibodies, primarily eliminates extracellular microbes.

85.

Question: What is Cell-Mediated Immunity mediated by? Answer: Different types of T lymphocytes (Helper and Cytotoxic), recruits phagocytes, kills infected cells, primarily eliminates intracellular pathogens.

86.

Question: What is Clonal Selection? Answer: The process where a specific lymphocyte (B or T cell) with a receptor that recognizes a foreign antigen is selected from a diverse pool and proliferates.

87.

Question: Clonal Expansion Process? Answer: Selected lymphocytes undergo multiple cycles of cell division to produce a clone of cells with the same specificity.

88.

Question: Simplified Antibody-Mediated Immune Response Process? Answer: Naive B cell recognizes antigen via surface Ig (BCR). B cell processes antigen and presents on MHC II. Helper T cell recognizes antigen on B cell. Helper T cell activates B cell. Activated B cell proliferates (clonal expansion). B cells differentiate into plasma cells and memory cells. Plasma cells secrete antibodies. Antibodies clear antigen by neutralization, opsonization, or complement activation.

89.

Question: Simplified Cell-Mediated Immune Response Process? Answer: Infected host cell degrades intracellular pathogen into antigens. Antigen fragments bind to MHC Class I. Peptide-MHC I complex presented on cell surface. Cytotoxic T cell recognizes complex. Cytotoxic T cell activated and kills infected cell (e.g., by inducing apoptosis).

90.

Question: What is the defining feature of adaptive immunity created by V(D)J recombination? Answer: Antibody and TCR diversity.

91.

Question: Where does V(D)J recombination occur? Answer: In developing lymphocytes during T- and B-cell maturation in primary lymphoid organs (bone marrow and thymus).

92.

Question: What are lymphocytes? Answer: Cells involved in adaptive immunity (B cells, T cells) and some innate immunity (NK cells), derived from lymphoid lineage stem cells.

93.

Question: What are the primary lymphoid organs? Answer: Bone marrow and thymus.

94.

Question: What are the secondary lymphoid organs? Answer: Lymph nodes, spleen, mucosal-associated lymphoid tissue (MALT).

95.

Question: What kind of immunity is provided by IgG in mammals? Answer: Provides bulk of specific adaptive immunity against bacteria and viruses in ECF.

96.

Question: What kind of immunity is provided by IgA in secretions? Answer: Protects mucosal surfaces by binding to antigens and blocking attachment of pathogens.

97.

Question: What kind of immunity is provided by IgA in breast milk and IgG across the placenta? Answer: Passive immunity to the baby.

98.

Question: How is passive immunity different from active immunity? Answer: Passive immunity is short-lived with no memory, while active immunity generates immunological memory.

99.

Question: What are common immunohistochemistry techniques using antibodies? Answer: ELISA and Immunoblotting.

100.

Question: What technology is used for monoclonal antibody production? Answer: Hybridoma technology.

101.

Question: What is a hybridoma? Answer: A composite cell formed by fusing an activated B cell with a cancerous myeloma cell, capable of producing monoclonal antibodies. They are immortalized.

102.

Question: What are monoclonal antibodies? Answer: Highly specific antibodies produced by a single clone of hybridoma cells, specific for a single epitope.

103.

Question: What are polyclonal antibodies? Answer: Antibodies produced by multiple B cell clones, recognizing multiple epitopes on an antigen.

104.

Question: What is an autoimmune disease? Answer: A malfunction where the immune system reacts against the body's own proteins or cells.

105.

Question: Examples of autoimmune diseases? Answer: Type 1 diabetes, Lupus, Rheumatoid arthritis, Multiple sclerosis.

106.

Question: What is an allergic reaction? Answer: An immune system malfunction involving a severe inflammatory response to normally harmless antigens (allergens), often mediated by IgE antibodies and histamine release from mast cells/basophils.

107.

Question: What are allergens? Answer: Substances that trigger allergic reactions.

108.

Question: What do mast cells and basophils release in allergic reactions? Answer: Histamine.

109.

Question: What is anaphylactic shock? Answer: A severe, life-threatening allergic reaction involving airway constriction and a drop in blood pressure.

110.

Question: What are the three lines of defense in mammals against pathogens? Answer: Anatomical barriers, Innate immunity, Adaptive immunity.

111.

Question: Examples of anatomical barriers? Answer: Skin, epithelial barrier, antimicrobial peptides (lysozymes, defensins), biological microbiome.

112.

Question: What is the microbiome? Answer: Normal array of microorganisms in the body that inhibit colonization by pathogens.

113.

Question: What is Innate Immunity? Answer: Nonspecific defenses present from birth that combat pathogens. Responds rapidly. Does not have memory.

114.

Question: What are the main strategies of the innate immune system against viral pathogens? Answer: Interferon and Natural killer cells.

115.

Question: What are Natural Killer (NK) cells? Answer: Lymphoid lineage cells of the innate immune system that kill virus-infected cells and cancer cells.

116.

Question: How do NK cells distinguish normal cells from infected cells? Answer: They monitor the level of MHC proteins; low MHC targets the cell for destruction, high MHC inhibits killing.

117.

Question: What are interferons? Answer: Cytokines (signaling proteins) produced by cells in defense against viruses, interfere with viral replication.

118.

Question: What is Adaptive Immunity? Answer: Specific defenses developed after exposure to pathogens or foreign substances. Characterized by specificity, diversity, and memory.

119.

Question: What is specificity in adaptive immunity? Answer: The ability to recognize and respond to a particular antigen or epitope.

120.

Question: What is diversity in adaptive immunity? Answer: The ability to recognize an enormous range of antigens, generated primarily by V(D)J recombination.

121.

Question: What is a pathogen? Answer: A disease-causing virus, bacteria, protist, fungi, or parasite.

122.

Question: What is immunology the study of? Answer: The immune system, immune response, cellular and molecular events that ensues a microbial attack or other foreign macromolecules.

123.

Question: How do anatomical barriers help prevent infection? Answer: By providing a physical barrier and producing antimicrobial substances.

124.

Question: How does innate immunity combat cellular pathogens? Answer: By using nonspecific defenses such as phagocytosis and the complement system, often recognizing pathogen-associated molecular patterns (PAMPs).

125.

Question: Why is innate immunity considered a nonspecific defense? Answer: It combats pathogens generally rather than targeting a specific antigen.

126.

Question: What are cytokines? Answer: Proteins that coordinate many activities of immune cells, small signaling molecules.

127.

Question: All types of formed elements of the blood develop from what cell type? Answer: A single cell type — stem cell (pluripotent stem cells or hemocytoblasts).

128.

Question: What are macrophages? Answer: Phagocytic cells derived from monocytes that ingest and kill microbes, ingest dead cells, secrete cytokines, and serve as antigen presenting cells (APCs).

129.

Question: What is the major function of macrophages? Answer: To ingest and kill microbes by generation of reactive oxygen species (ROS) and proteolytic digestion.

130.

Question: What do activated macrophages secrete? Answer: Cytokines which instruct other cells that contribute to host defense.

131.

Question: How are T cells different from B cells in antigen recognition? Answer: T cells require antigens to be processed and presented on the surface of APCs in the context of MHC molecules, whereas B cells can bind directly to free antigens via their surface antibodies (BCRs).

132.

Question: Where are B cells and T cells matured respectively? Answer: B cells mature in the bone marrow, and T cells mature in the thymus.

133.

Question: What are CD markers (CD4, CD8)? Answer: Glycoproteins present on the cell surface of T cells, used to classify them.

134.

Question: What types of pathogens does MHC Class I presentation help eliminate? Answer: Intracellular pathogens like viruses and some bacteria.

135.

Question: What types of pathogens does MHC Class II presentation help eliminate? Answer: Extracellular pathogens.

136.

Question: How are extracellular pathogens taken up for MHC Class II presentation? Answer: By endocytic process by phagocytic cells.

137.

Question: What happens within the phagosome during antigen processing? Answer: Antigens are degraded.

138.

Question: Where does the assembly of the peptide-MHC complex take place? Answer: In the cell where the antigen is processed.

139.

Question: What happens once the peptide-MHC complex is formed? Answer: It is transported to the cell surface and accessible to TCRs on T cells.

140.

Question: What are cells carrying antigen-MHC complexes known as? Answer: Antigen presenting cells (APCs).

141.

Question: Do any two individuals have the same combination of MHC proteins on their body cells (except identical siblings)? Answer: No.

142.

Question: What induces a B cell to proliferate and differentiate into a plasma cell? Answer: Signals from the bound antigen and from the helper T cell.

143.

Question: How long does it typically take for the first antibodies to appear in the blood during a primary immune response? Answer: 3 to 14 days.

144.

Question: Compared with active immunity, how long does passive immunity typically last? Answer: A short-lived phenomenon, antibodies typically break down within a month.

145.

Question: How do Natural Killer cells distinguish normal cells from infected cells? Answer: A high level of "self" tags (MHC proteins) on normal cells inhibits killing, while a low level (as on virus-infected or cancer cells) targets the cell for destruction.

146.

Question: What process generates the diversity of antibody molecules and T cell receptors? Answer: Somatic gene recombination (VDJ recombination).

147.

Question: What are the gene segments involved in antibody diversity generation? Answer: V (variable), D (diversity - heavy chain only), and J (joining) segments.

148.

Question: How does RNA processing contribute after VDJ recombination? Answer: Transcription creates pre-mRNA, which undergoes processing (removal of introns, etc.) to produce functional mRNA that is translated into polypeptide chains.

149.

Question: Where are IgM and IgD typically found? Answer: As cell surface antigen receptors on circulating B cells.

150.

Question: What is the most abundant antibody circulating in the blood and lymphatic system? Answer: IgG.

151.

Question: What is IgG also known as? Answer: The gamma globulin fraction of plasma.

152.

Question: What are the cardinal signs of inflammation? Answer: Redness (Rubor), Swelling (Tumor), Heat (Calor), Pain (Dolor).

153.

Question: What mediates the signs of inflammation? Answer: Chemical mediators, cytokines, etc.

154.

Question: What are Pattern Recognition Receptors (PRRs)? Answer: Receptors on innate immune cells that recognize conserved molecular patterns (PAMPs) on pathogens.

155.

Question: What are Pathogen-Associated Molecular Patterns (PAMPs)? Answer: Conserved molecules or structures present on pathogens that are recognized by PRRs on innate immune cells.

156.

Question: Examples of PRRs? Answer: Toll-like receptors, Mannose receptors, Scavenger receptors.

157.

Question: What is Hematopoiesis? Answer: The process by which all formed elements of the blood develop from pluripotent stem cells.

158.

Question: What are the two main lineages of blood cells? Answer: Myeloid lineage and Lymphoid lineage.

159.

Question: What cells come from the Myeloid lineage? Answer: Erythrocytes, Platelets, Granulocytes (Neutrophils, Eosinophils, Basophils), Monocytes.

160.

Question: What cells come from the Lymphoid lineage? Answer: B cells, T cells, Natural Killer (NK) cells.

161.

Question: What are monocytes? Answer: Myeloid lineage cells that circulate in the blood and differentiate into macrophages in tissues.

162.

Question: What are granulocytes? Answer: Myeloid lineage cells containing cytoplasmic granules (e.g., neutrophils, eosinophils, basophils).

163.

Question: What is the nucleus shape of neutrophils? Answer: Lobed, multi-lobed (polymorphonuclear).

164.

Question: What is the nucleus shape of monocytes? Answer: Kidney-shaped or horseshoe-shaped.

165.

Question: What is the nucleus shape of lymphocytes? Answer: Large, round nucleus with scant cytoplasm.

166.

Question: What is phagocytosis? Answer: The process by which a cell engulfs and ingests particles or microbes ("cell eating").

167.

Question: What are phagocytic cells? Answer: Cells that perform phagocytosis, including macrophages, dendritic cells, neutrophils.

168.

Question: What are osteoclasts? Answer: Bone-resorbing cells derived from monocytes/macrophages.

169.

Question: What are tissue-specific macrophages? Answer: Macrophages in different tissues with specific names (e.g., microglia in CNS, Kupffer cells in liver, alveolar macrophages in lungs).

170.

Question: What is the major function of IgE against parasites? Answer: Binds to parasite antigens, then binds to receptors on mast cells and eosinophils, triggering release of mediators that damage parasites.

171.

Question: What is the typical secreted form of IgG? Answer: Monomer.

172.

Question: What is the typical secreted form of IgD? Answer: Monomer.

173.

Question: Are B cell receptors (BCRs) soluble or membrane-bound? Answer: Membrane-bound immunoglobulins.

174.

Question: Do T cell receptors (TCRs) bind directly to soluble antigens? Answer: No, they require processed antigens presented on MHC molecules.

175.

Question: What happens to plasma cells after an infection is cleared? Answer: They typically die.

176.

Question: What happens to memory cells after an infection is cleared? Answer: They remain in the body, providing immunological memory.

177.

Question: Can non-infectious substances trigger immune responses? Answer: Yes, such as proteins, lipids, polysaccharides, or artificially synthesized molecules.

178.

Question: What is immunodeficiency? Answer: Results from failure or absence of elements of the immune system.

179.

Question: What is the primary line of defense against pathogens? Answer: Anatomical barriers like skin and mucus membranes.

180.

Question: What kind of immunity provides the bulk of immunity against bacteria and viruses in extracellular fluid? Answer: Specific adaptive immunity, primarily mediated by IgM and IgG.