Thymus-independent anti-DNP antibody responses to DNP-casein and DNP-gelatin

Although studies on the molecular nature of thymus-independent antigens suggested that the polymeric structure with repeated antigenic determinants and slow metabolism are responsible for thymus-independence, we found that anti-DNP antibody responses to DNP-casein and DNP-gelatin were thymus-independent as well as macrophage-independent. These antibody responses were not affected by in vivo treatment with carrageenan or anti-thymocyte serum. In addition, responses of athymic nude mice to both antigens did not show any significant differences when compared with heterologous nu/+ mice. The findings were confirmed by in vitro experiments; non-adherent spleen cells or T cell-depleted spleen cells responded well to both antigens to the same extent as normal spleen cells. Since both casein and gelatin are polyclonal B cell activators and are not presumed to be high polymer or slow-metabolizing substances, we suggest that thymus-independence in many kinds of antibody response should be reconsidered.