Subclass restriction of murine antibodies. II. The IgG plaque-forming cell response to thymus-independent type 1 and type 2 antigens in normal mice and mice expressing an X-linked immunodeficiency.

Abstract

Antigens were classified previously into 3 categories, thymus-dependent (TD), thymus-independent type (TI) 1, and TI-2, based upon thymic dependence and ability to stimulate an immunodeficient strain of mouse, CBA/N. The different antigen classes elicited Ig[immunoglobulin]G antibodies of different subclasses. TD antigens stimulate predominantly IgG1 antibodies, with smaller amounts of IgG2 and IgG3 being expressed. TI-1 antigens stimulate almost no IgG1 antibodies and equal amounts of IgG2 and IgG3. TI-2 antigens elicited predominantly IgG3 antibodies. Mice expressing the CBA/N phenotype are nonresponsive to TI-2 antigens. This was confirmed in this study. The IgG3 component of the response to TI-1 antigens was virtually absent in mice expressing the CBA/N phenotype, which supports the previous finding that the CBA/N defect may be restricted to a B[bone marrow-derived]-lymphocyte subpopulation containing most of the precursors of IgG3-secreting cells.