1 Which of the following does not protect body surfaces:
C Gastric acid.
D Salivary amylase
E Gut microflora.
Correct. The enzyme splits starch and is of importance for digestion but not for protection.
2 Pattern recognition receptors (PRR) include:
C Lipoteichoic acid.
D Lectin-like molecules.
E Unmethylated CpG sequences.
Correct. Many PRR are lectin-like in that they recognize exposed microbial sugars.
3 The mononuclear phagocyte system does not include:
B Kupffer cells.
C Kidney mesangial cells.
D Lymph node medullary macrophages.
E Endothelial cells.
Correct. Endothelial cells are not essentially phagocytic although they do contribute by the production of mediators of the inflammatory process, particularly acute inflammation and were previously lumped together with the mononuclear phagocyte system in what was known as the reticuloendothelial system (RES).
4 A polymorphonuclear neutrophil (PMN):
A Is a bone marrow stem cell.
B Is closely similar to a mast cell.
C Contains microbicidal cytoplasmic granules.
D Is not a professional phagocytic cell.
E Has granules which stain with eosin.
Correct. The granules contain a wide spectrum of microbicidal agents.
5 Which of the following is not produced following activation of the NADPH oxidase microbicidal pathway
A O2 –
Correct. NO is produced following the induction of nitric oxide synthase.
8 Complement component C3 is cleaved by:
C Factor B
D Factor D
E Factor H
Correct. This is the C3 convertase enzyme generated in the alternative complement pathway and is responsible for splitting off the small peptide C3a leaving C3b as a residue.
1 The basic Ig unit is composed of:
A 2 identical heavy and 2 identical light chains.
B 2 identical heavy and 2 different light chains.
C 2 different heavy and 2 identical light chains.
D 2 different heavy and 2 different light chains.
E Non-covalently bound polypeptide chains.
2 A Fab fragment:
A Is produced by pepsin treatment.
B Is produced by separation of heavy and light chains.
C Binds antigen.
D Lacks light chains.
E Has no interchain disulfide bonds.
Correct. Fab = fragment antigen binding
3 The complementarity determining regions:
A Are restricted to light chains.
B Are in the constant part of the Ig molecule.
C Bind to Fc receptors.
D Are concerned in antigen recognition.
E Occur at the C-terminal end of the Ig peptide chains.
Correct. 3 CDR’s in the heavy and 3 in the light chain may all be concerned in forming the antigen recognition structure.
4 Which of the following gene clusters do not contribute to antigen binding:
Correct. The constant region genes encoding the constant region of the light chain do not bear antigen binding CDR’s.
5 Recombination of V, D and J Ig gene segments:
A Only occurs in mature B-cells.
B Only occurs in light chains.
C Involves heptamer-spacer-heptamer flanking sequences.
D Does not occur until the mRNA stage.
E Is effected by recombinase enzymes.
Correct. The RAG-1 and RAG-2 encoded recombinase enzymes are critically involved in the gene rearrangement process.
6 Ig idiotypes are found:
A In the constant region of the heavy chain.
B In the constant region of the light chain.
C In the hinge region.
D In the variable region of both heavy and light chains.
E Only in the light chain.
Correct. Idiotypes are the collection of epitopes on the variable region of an immunoglobulin which are recognized by a collection of antibodies directed against them (the so-called anti-idiotypic serum).
8 Which of the following statements does not apply to IgG?:
A Appears early in the primary immune response.
B Neutralizes bacterial toxins.
C Can fix complement.
D Crosses the human placenta.
E Opsonizes bacteria.
Correct. IgM is the class which appears early following the first encounter with a specific antigen.
A Is usually of high affinity.
B Is most commonly tetrameric.
C Has the same number of constant domains as IgG.
D Is a weak bacterial agglutinator.
E Is the main class of the ‘natural antibodies’.
Correct. The natural antibodies which include many anti-bacterial antibodies, arise largely without external antigenic stimulation. In the mouse they are made by the CD5+ B1 subset.
A Is pentameric.
B Is resistant to proteolytic degradation.
C Is present mainly as a surface receptor on B-cells.
D Is present with unusual frequency in myelomas.
E Is abundant in milk
Correct. Naive B-cells coexpress surface IgM and IgD of the same antigen specificity.
A Is abundant in saliva.
B Binds strongly to mast cells.
C Cannot bind to macrophages.
D Activates the complement cascade.
E Has an insignificant role in worm infestations
Correct. The Fc epsilon receptor on mast cells, Fc epsilon RI, binds IgE very strongly and cross-linking by antigen leads to mast cell activation and initiation of an inflammatory reaction.