Unit 2: Antigens; Immunoglobulins (Antibodies) - Practice Quiz

1 What is an antigen?

2 Which term describes a substance capable of inducing an immune response on its own?

3 Which statement about immunogens and antigens is correct?

4 Which property generally makes a molecule more immunogenic?

5 Which factor increases the immunogenicity of a substance?

6 Which class of molecules is typically the most immunogenic?

7 What is an epitope?

8 An epitope that is formed by amino acids brought together by protein folding is called a:

9 What is a hapten?

10 To make a hapten immunogenic, it must be attached to a:

11 A typical antibody monomer is composed of how many polypeptide chains?

12 Which region of the antibody is responsible for binding to the antigen?

13 The two types of light chains found in antibodies are:

14 Which immunoglobulin is the most abundant in human serum?

15 Which immunoglobulin is the first to be produced during a primary immune response?

16 Which immunoglobulin is mainly associated with allergic reactions and defense against parasites?

17 Which immunoglobulin is the predominant antibody found in mucosal secretions such as saliva and tears?

18 Which immunoglobulin can cross the placenta to provide passive immunity to the fetus?

19 The term antigenic determinant is another name for:

20 Which process is a major source of antibody diversity?

21 A researcher injects a small chemical group coupled to a large protein into a mouse and detects antibodies against the small chemical group. When the small chemical group is injected alone, no antibodies are produced. Which statement best explains this observation?

22 Two proteins of similar molecular weight are compared. Protein X is highly identical to a mouse self-protein, while Protein Y differs substantially from any mouse protein. When both are injected into mice, which is expected to be more immunogenic and why?

23 Penicillin can trigger allergic reactions in some patients even though it is a small molecule. Which mechanism best explains how penicillin becomes immunogenic in the body?

24 An antibody recognizes a region of a folded protein formed by amino acids that are far apart in the primary sequence but close together in 3D space. What type of epitope is this?

25 A protein antigen is treated with a denaturing agent that unfolds it. After denaturation, an antibody that previously bound the native protein no longer binds. This antibody most likely recognized a:

26 Treating an IgG molecule with the enzyme papain yields how many and what type of fragments?

27 Pepsin digestion of IgG differs from papain digestion. What is the main product of pepsin cleavage?

28 During a secondary immune response, which immunoglobulin class predominates and reflects immunological memory?

29 A nursing infant receives protection at mucosal surfaces through breast milk. Which immunoglobulin is primarily responsible for this passive mucosal immunity?

30 A patient shows elevated levels of an antibody bound to mast cells and involved in a hypersensitivity reaction to pollen. Which immunoglobulin is most likely elevated?

31 Which immunoglobulin is the most efficient at activating the classical complement pathway due to its pentameric structure?

32 Which immunoglobulin can cross the human placenta to provide passive immunity to the fetus?

33 Which process rearranges separate gene segments to create a functional variable region and is a major source of antibody diversity before antigen exposure?

34 After antigen exposure in the germinal center, point mutations accumulate in the variable regions of antibody genes, improving antigen binding. This process is known as:

35 The imprecise addition or removal of nucleotides at the joints between recombined V, D, and J segments contributes to which type of diversity?

36 A large protein antigen can stimulate the production of many different antibodies simultaneously. What term best describes this property?

37 Why are large proteins generally more immunogenic than small polypeptides of the same chemical nature?

38 A substance binds specifically to a T-cell receptor or antibody but requires processing and MHC presentation to activate T cells. Which term best describes a molecule recognized specifically by the adaptive immune system?

39 In a classic hapten-carrier experiment, mice are immunized with hapten A coupled to carrier P. A strong secondary response to hapten A requires that the animal is re-challenged with:

40 In an immunoglobulin monomer, where is the antigen-binding specificity primarily determined?

41 A synthetic polymer of 8 amino acids is injected into a mouse and fails to elicit any antibody response, yet when preformed antibodies against this polymer are added in vitro, they bind it specifically with high affinity. Which conclusion is most accurate?

42 In Landsteiner's classic hapten-carrier experiments, dinitrophenol (DNP) coupled to bovine serum albumin (BSA) elicits anti-DNP antibodies. If a mouse is primed with DNP-BSA and later boosted with DNP conjugated to ovalbumin (OVA), the secondary anti-DNP response is weak. What explains this?

43 Consider a hypothetical Ig heavy chain locus with 40 V, 25 D, and 6 J segments. Ignoring junctional diversity and heavy-light pairing, how many distinct VDJ combinations are possible, and which mechanism adds the most diversity beyond this figure?

44 A patient with a selective IgA deficiency is generally protected against many mucosal pathogens. Which compensatory mechanism most plausibly accounts for retained mucosal immunity?

45 Papain and pepsin cleave IgG at different sites relative to the hinge disulfide bonds. Which statement correctly contrasts the functional fragments produced?

46 An antibody binds a native protein but loses all reactivity after the protein is boiled and reduced. A second antibody binds equally well to the native and denatured forms. What is the best interpretation?

47 Two proteins of identical molecular weight are injected into genetically identical mice with the same adjuvant and dose. Protein X is a highly conserved mammalian housekeeping enzyme; protein Y is a bacterial toxin. Protein Y is far more immunogenic. Which factor best explains the difference?

48 The RAG1/RAG2 complex introduces double-strand breaks at recombination signal sequences (RSS). Efficient recombination requires the '12/23 rule.' What does this rule enforce?

49 During a secondary immune response, class switch recombination (CSR) alters the antibody isotype but preserves antigen specificity. Which molecular feature guarantees that specificity is retained after switching from IgM to IgG?

50 Isotypic, allotypic, and idiotypic determinants distinguish immunoglobulin variants. An anti-idiotypic antibody raised against one monoclonal antibody's variable region can sometimes act as an 'internal image' of the original antigen. Which principle underlies this?

51 For a globular protein antigen, the number of epitopes recognized by antibodies (the antigenic 'valence') is often much lower than the theoretical number of surface patches. Which factor most limits the functional epitope number?

52 IgG affinity for antigen depends on the intrinsic binding of a single Fab, whereas avidity depends on multivalent binding. If a monovalent Fab has M and the intact bivalent IgG shows an apparent M for a multivalent antigen, which term best describes this -fold enhancement?

53 IgE is present in serum at the lowest concentration of all isotypes yet mediates potent immediate hypersensitivity. Which structural/receptor feature best accounts for its disproportionate biological effect?

54 Somatic hypermutation (SHM) and class switch recombination (CSR) both require activation-induced cytidine deaminase (AID). What is AID's direct enzymatic action, and why do both processes depend on it?

55 Penicillin causes drug allergy because its reactive β-lactam ring covalently modifies host proteins. In immunological terms, penicillin acts as which entity, and what is the role of the host protein?

56 A very high dose of a soluble protein antigen given without adjuvant induces a state of specific unresponsiveness rather than immunity. This phenomenon is best described as:

57 T-independent type 2 (TI-2) antigens such as bacterial polysaccharides can activate B cells without cognate T-cell help. Which property of these antigens enables this, and what is a typical consequence for the response?

58 Allotypic determinants of immunoglobulins are used in paternity and forensic studies. Which statement correctly characterizes allotypes?

59 Adjuvants are frequently required to convert a purified protein into an effective vaccine immunogen. Which best explains why the same protein may be antigenic without an adjuvant yet only weakly immunogenic?

60 The hinge region of IgG confers segmental flexibility but is absent in IgM. Which functional consequence best follows from IgM lacking a classical hinge yet still binding multivalent antigen effectively?