The following graph shows the sequential alteration in the type and amount of antibody produced after an immunization. (Inoculation of anti gen occurs at two different times, as indicated by the arrows.) Curve A and curve B each represent a distinct type of antibody. The class of immuno globulin represented by curve B has which of the following characteristics? (AIIMS Nov 10)
|A||A composition of four peptide chains connected by disulfide links.|
|B||A symmetric dipeptide|
|C||An appearance in neonates at approximately the third month of life|
|D||The human ABO isoagglutinin|
a. The graph presented in the question exhibits hemagglutinating antibody responses to primary and secondary immunization with any standard antigen.
b. Curve B represents the early response to primary immunization, which is chiefly an IgM response.
c. Rechallenge elicits an accelerated response that mainly involves IgG and occurs two to five days after reimmunization.
d. IgM has a molecular weight of 900,000 and is a pentamer that the fetus can pro duce quite early in gestation. 1gM (and IgG) have the ability to activate complement, appear along with sIg D as the B cell receptor on B lymphocytes, and like IgA require J chains to join the Fc chains of each monomer together.