- During the initial days of lactation the yellowish fluid wlostrum is secreted by mother. It has abundant antibodies (IgA) that protects the infant from several diseases. IgG immunoglobulin (antibody) is most abundant (appro. \( 80 \% \) antibody in human and found in serum IgA is second abundant (approx. 10-15\%) antibody. It is found in saliva and tear also. IgD and IgE constitute 2-3\% of total antibodies which are found in most cells and serum.