Immunoglobulins in the Normal State and in Neoplasms of B Cells

Abstract

The major function of plasma cells, and to a lesser extent of lymphocytes, is to produce immunoglobulins (Ig’s). Since these molecules play a major role in the defense of the body against a variety of infectious agents, it does not come as a surprise that there is no other group of molecules with such extreme heterogeneity. This heterogeneity can be viewed on several levels. First, in most vertebrate species, there are several major classes and subclasses of Ig’s. In man, these are IgG, IgA, IgM, IgD, and IgE. The properties of the major classes and subclasses are listed in Table 1. In the case of IgG, we know of four well-recognized subclasses (IgGl, -2, -3, and -4). There are two subclasses of IgA (IgAl and -2). Subclasses of IgM and IgD are as yet less well defined, but it would appear that for IgM there may be several, and in the case of IgD, there appear to be two. As yet, no subclasses have been recognized for IgE. These major classes and subclasses of Ig’s appear to have evolved one from the other as manifested by the striking structural homologies among them (Natvig and Kunkel, 1973; Fudenberg et al 1972; Solomon and McLaughlin, 1973). The next level of heterogeneity is somewhat more subtle, in that it reflects genetic polymorphisms that have recognized for several of the Ig classes and subclasses and presumably exist for all of them (Fudenberg et al., 1972). Last is the very complex heterogeinity related to antibody specificity (Wu and Kabat, 1970; Capra and Kehoe, 1975; Pawlak et al., 1973; Rudikoff et al., 1973).