Subclass restriction of murine antibodies: V. The IgG plaque-forming cell response to thymus-independent and thymus-dependent antigens in athymic and euthymic mice

Antigens differ in their abilities to stimulate antibodies of various isotypes. Many thymus-independent (TI) polysaccharide antigens stimulate largely IgG3 and IgM antibodies while thymus-dependent (TD) protein antigens stimulate predominantly IgG1 and smaller amounts of other isotypes. Here we determine whether thymus dependence or independence is a property of antigens which is expressed equally by all isotypes. To do this nu/+ and nu/nu mice were immunized with several TI and TD antigens and antibody responses of IgM and the four IgG subclasses measured. We found that, within the conditions of these experiments, all IgG isotypes were influenced equally by the presence or absence of T lymphocytes. Second, in agreement with J. L. Press (J. Immunol.126, 1234, 1981), we propose a division of TD antigens into two types based upon the ability to stimulate responses in the CBA/N mouse.