Question

41. The secondary, but not the primary, immune response is based on:                                                                     

A. Memory                                                       

B. The bonus effect of multivalency                                                                

C. Complement activation                            

D. Mast cell degranulation                                                                

E. Clonal selection

42. 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

43. IgD:                                                                                                                                                                        

A. is pentameric                                                   

B. is resistant to proteolytic degradation                                                                                                                     

C. is present mainly as a surface receptor on B-cells                                                                                             

E. is abundant in milk

Answer 1

Answer 41- a) Memory

Reason- Secondary immune response occurs when the individual encounters the same antigen again. It is based on the growth of memory cells, which can recognise the pathogen that previously infected the individual.

Answer 42- a) 2 identical heavy and 2 identical light chains.

Reason- Ig is a bilaterally symmetrical molecule that is made up of four polypeptide chains i.e 2 identical light and 2 identical heavy chains. The heavy and light chains are linked by interchain disulfide bonds.

Answer 43- c) is present mainly as a surface receptor on B-cells.

Reason- it is a monomeric antibody found on the plasma membranes of immature B-lymphocytes as receptors.IgD has increased susceptibility to proteolysis.