True about location of Ig chromosome:

A i.e. lc- 2In humans, genes for light chains-Kappa (lc) is in chromosome 2; for light chain lambda (X) is in chromosome 22 and genes for heavy chains are in chromosome 14Q.Each of the 5 classes of immunoglobulin has a characterstic type of heavy chain - alpha (a) in IgA, gamma (y) in IgG, delta (8) in IgD, mu (.t) in IgM and epsilon (c) in IgE.Immunoglobin has 2 identical light (L) & 2 identical heavy (H) chains, each containing variable (V) & constant (C) regions. Variable regions of light- & heavy chains (i.e. VL & VH) bind to specifc antigen and form a pa of Fab (antigen binding fragment).IgM is natural antibody produced in primary response to antigen. It does not cross placenta, therefore, the fetus even though it carries an incompatible antigen, is protected from natural antibodies of mother. It fixes complementQ (like IgG) and agglutinates bacteria (like IgA & G). It has antigen receptors on B cells, surface (IgD is found on surface of B cells where it acts as a receptor for antigen).Newly mature B cells produce both IgM and IgD, which can switch to other class of immunoglobulin (i.e. IgG, IgA or IgE) in a process k/a isotype/class switching.