Alterations in Isotypic and Allotypic Immunoglobulin Antigens Induced by Chemical Modification

Gamma G myeloma and Bence Jones protein were modified by amidination, a treatment specific for ε-amino groups of lysine, and tested before and after modification for their serologic reactivity with antisera against defined γ and light chain antigens. Gm(a), “non-a”, Gm(z), Inv(a), and Oz(+) reactivity but not that of Gm(f), (b0), (g) or “non-g” were inactivated by this treatment. Lysine residues are known to be directly involved or lie immediately adjacent to the amino acid positions responsible for expression of all the antigens altered by amidination. It is suggested that the use of chemical probes specific for various amino acid resides may be of benefit in defining the structures responsible for the serologically-defined antigens of human immunoglobulins.