السلام عليكم ورحمة الله وبركاته
اقدم اليكم هذا الرابط عسى الله ان ينفعنا وايكم





مع خالـــــــــــــــــــــــــــــــص تحياتي
السنوسي احموده احمد
اخصائي تحاليل طبيه
سبها //// ليبيا


sonuci_2010 libya --- sebha

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Question 1 A bacterial infection would be expected to result in the production of IgG antibodies to the protein components, IgM antibodies to the polysaccharide components and IgG antibodies to the lipid components of the bacteria
• True
• (X)(*)False
(X) Your Answer.(*) Correct Answer.

Explanation: IgG antibodies would be expected to be made to the protein components, since proteins are usually T-dependent antigens and class switching will occur. IgM antibodies would be expected to be made to the polysaccharide components, since polysaccharides are usually T-independent antigens and class switching will not occur. Antibodies would not be expected to be made to lipids since they are usually very poor immunogens

Question 2 Antibodies and B cells can recognize both conformational and sequence determinants
• (X)(*)True
• False
(X) Your Answer.(*) Correct Answer.

Explanation: B cells and the antibodies produced by them will recognize sequence and conformational determinants, whereas T cells only recognize sequence determinants on proteins

Question 3 Administration of a hapten will not result in the production of anti-hapten antibodies but administration of a mixture of a hapten and a protein would
• (X)True
• (*)False
(X) Your Answer.(*) Correct Answer.

Explanation: The hapten must be covalently coupled to the protein to create hapteneic determinants that will be immunogenic. Simple mixing the hapten and protein will not elicit an immune response to the hapten

Question 4 IgE is important in protection from helminthic (worm) infections due to its ability to participate in complement-mediated lysis of the parasites
• (X)True
• (*)False
(X) Your Answer.(*) Correct Answer.

Explanation: IgE is not a complement fixing antibody. IgE does, however, participate in protection from worm infections because it binds to Fc receptors on eosinophils, which results in the release of granules, which are toxic to worms

Question 5 Fab fragments lack isotypic determinants
• (X)True
• (*)False
(X) Your Answer.(*) Correct Answer.

Explanation: There are isotypic determinnats on the constant region of the light chains, which are part of the Fab fragment

Question 6 F(ab’)2 fragments can be used as the antibody in an agglutination test but Fab fragments cannot
• (X)(*)True
• False
(X) Your Answer.(*) Correct Answer.

Explanation: True since F(ab’)2 fragments are divalent whereas Fab fragments are not. Both the antigen and the antibody must be multivalent for lattice formation (agglutinantioin) to occu

Question 7 Immunoglobulin classes are determined by the constant region of the heavy chain and the subclasses are determined by the constant region of the light chain
• True
• (X)(*)False
(X) Your Answer.(*) Correct Answer.

Explanation: Immunoglobulin classes and subclasses are both determined by the constant region of the heavy chain

Question 8 An IgG molecule may be composed of two identical heavy chains and a kappa and lambda light chain with identical variable regions
• True
• (X)(*)False
(X) Your Answer.(*) Correct Answer.

Explanation: All IgG molecules are composed of two identical heavy and two identical light chains, since the B cell that makes the immunoglobulin only expresses one heavy and one light chain. Thus, an IgG could not have both a kappa and a lambda chain

Question 9 The specificity of the immunoglobulin is determined by the constant regions of heavy and light chains
• True
• (X)(*)False
(X) Your Answer.(*) Correct Answer.

Explanation: The specificity is determined by the heavy and light chain hypervariable regions, which are located in the variable region of the molecule. The constant regions determine the effector function

Question 11 A Km1/Km1 mother gives birth to a Km1/Km3 child and claims that the father is her live-in boyfriend who is Km1/Km1. She is correct in her assertion that her boyfriend is the father
• (X)True
• (*)False
(X) Your Answer.(*) Correct Answer.

Explanation: Since the mother is homogygous Km1 and the child is heterogygous Km1/Km3, the child’s father must have the Km3 allele. Since the live-in boy friend does not have a Km3 allele he is not the fathe

Question 12 The heavy and light chain hypervariable regions determine the affinity, specificity, and idiotype of the immunoglobulin
• (X)(*)True
• False
(X) Your Answer.(*) Correct Answer.

Explanation: The heavy and light chain hypervariable regions determine: (1) which antigen will bind to the antibody (specificity); (2) how tightly the antigen will bind to the antibody (affinity); and (3) the antigenic determinants that are unique to that particular antibody (idiotype

Question 13 The equilibrium constant calculated for the reaction of a hapten and a Fab fragment is a measure of antibody avidity
• True
• (X)(*)False
(X) Your Answer.(*) Correct Answer.

Explanation: Avidity is the overall strength of binding between a multivalent antigen and a multivalent antibody. Since both haptens and Fab fragments are monovalent, the equilibrium constant for the reaction would be a measure of the affinity not the avidity

Question 14 A positive direct Coomb’s test indicates that a patient has antibodies on his/her erythrocytes
• (*)True
• (X)False
(X) Your Answer.(*) Correct Answer.

Explanation: The direct Coomb’s test evaluates whether a patient’s erythrocytes are coated with antibody whereas the indirect Coomb’s test evaluates whether a patient’s serum has antibodies to a particular erythrocyte

Question 15 The hemagglutination inhibition, immunoelectrophoresis and complement fixation tests depend on lattice formation
• True
• (X)(*)False
(X) Your Answer.(*) Correct Answer.

Explanation: The hemagglutination inhibition and immunoelectrophoresis tests do depend upon lattice formation but the complement fixation test does not

Question 17 VJ and VDJ rearrangement, combinatorial association and somatic mutation all contribute to the generation of antibody diversity
• (*)True
• False
(X) Your Answer.(*) Correct Answer.

Explanation: Antibody diversity refers to the total of all the different antibody specificities that and organism can make. VJ and VDJ rearrangement of the light and heavy chains, respectively, contribute to generation diversity as does combinatorial association of heavy and light chains. In addition, in B cells somatic mutation also contributes to generating diversity

Question 18 Production of a mature light chain requires DNA rearrangement, RNA processing (splicing) and proteolytic cleavage
• (*)True
• (X)False
(X) Your Answer.(*) Correct Answer.

Explanation: True, DNA rearrangement of the light chain genes, RNA processing during expression of the genes and proteolytic cleavage during transport of the nacent light chain into the lumen of the endoplasmic reticulum

Question 19 A defect in the Rag-1 or Rag-2 genes would result in B cells that can only make IgM antibodies
• True
• (X)(*)False
(X) Your Answer.(*) Correct Answer.

Explanation: A defect in the Rag genes would result in the inability to express an antigen receptor. Thus there would be no mature B cells and no antibodies made. In addition, there would be no T cells since the Rag genes are also used to rearrange the T cell receptor for antigen

Question 20 After class switching has occurred, B cells will make antibodies with the same specificity but different effector functions
• (X)(*)True
• False
(X) Your Answer.(*) Correct Answer.

Explanation: True, because the same VDJ region is used after class switching has occurred. Thus, the specificity of the antibody will not change. However the effector functions may change since a different constant region is present on the antibody after class switching

Question 21 Characteristics of a primary immune response to a T-dependent antigen include:
1) the production of primarily IgM antibodies,
2) the generation of memory B cells and T cells, and
3) sustained production of antibodies during the decline phase
• (X)True
• (*)False
(X) Your Answer.(*) Correct Answer.

Explanation: During the primary response there is production of primarily IgM antibodies and the generation of memory T and B cells but there is not sustained production of antibody in the decline phase. Sustained production of antibody during the decline phase is characteristic of the secondary response

Question 22 TOLL-like receptors are protein molecules on T-lymphocytes by which they interact with bacterial antigens
• True
• (X)(*)False
(X) Your Answer.(*) Correct Answer.

Explanation: Toll-like receptors are molecules on phagocytic and dendritic cells which recognize ligands on pathogens and the receptor-ligand interaction leads to activation of these cells leading to increased phagocytosis, intracellular killing and antigen processing and presentation

Question 23 Viruses that compromise tracheal mucociliary cell functions increase susceptibility to other pulmonary infections
• (*)True
• (X)False
(X) Your Answer.(*) Correct Answer.

Explanation: Many viruses retard muco-ciliary escalator movement and hence infections with these viruses is accompanied by secondary bacterial infections

Question 24 A defect in NADPH oxidase (cytochromb-558) impairs the chemotactic response and phagocytic activity of neutrophils
• (X)True
• (*)False
(X) Your Answer.(*) Correct Answer.

Explanation: Chronic granulomatous disease patients have defects in their NADPH oxidase genes. This results in various degrees of compromise of their ability to produce free radicals and hydrogen peroxide. Consequently, they are also incapable of producing myeloperoxidase-dependent antimicrobial molecules. Thus, intracellular microbicidal activity of their phagocytes is severely compromised, although their ability to respond to chemotactic stimuli and phagocytic function are normal. Due to persistence of organism in their system, these patients have dramatically increased number of circulating neutrophils

Question 25 C5a is one of the peptides that causes migration of phagocytic cells to the site of infection
• (X)(*)True
• False
(X) Your Answer.(*) Correct Answer.

Explanation: C5a is the most inflammatory molecule generated during C-activation. It is chemotactic and anaphylotoxic. It activates phagocytes, increasing their phagocytic activity, respiratory burst and intracellular killing function

Question 26 Bacteria that have certain mannose residues on their surface can cause the generation of C5-convertase (C4b2aC3b) in the absense of antibody
• (X)(*)True
• False
(X) Your Answer.(*) Correct Answer.

Explanation: Certain terminal mannose residues present on some bacterial surfaces can activate the complement cascade by binding MASP1 and MASP2. The activated mannose-MASP1-Masp2 complex serves as C4-C2 esterase, similar to Ag-Ab-C1qrs complex of the classical pathway, and leads to the lytic complex formation. Thus bacteria can be lysed by complement in the absence of antibody response

Question 27 The serum from an individual with defects in factor-I or factor-H will have a reduced CH50 level and increased susceptibility to many bacterial infections
• (*)True
• (X)False
(X) Your Answer.(*) Correct Answer.

Explanation: A defect in factor-I or factor-H can impair the degradation of spontaneously generated C3b. This will result in an uncontrolled consumption of C3, resulting in C3 depletion. Patients who have defect in these factors are extremely susceptible to infections since, in the absence of C3, they cannot produce any C5a that has crucial for an inflammatory response and progression of the lytic pathway
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