IN-VIVO STUDY OF MIGM AND MIGD CROSS-LINKING ON MURINE B-CELLS

In this study, we have analysed in mice the effects on the immune resp onse of in vivo treatment with different rat monoclonal antibodies (Mo Ab) against IgM and IgD. Although the effects of IgD crosslinking have been studied already, no attempt has been made to characterize the ef fects of in vivo IgM crosslinking, probably because of the higher IgM serum levels compared to IgD. We have used a panel of nine monoclonal rat anti-mouse IgM and three anti-IgD antibodies and we have character ized their isotypes, avidities, immunoglobulin (Ig) cross-linking and internalization abilities. Our results show that injection of mice wit h some rat MoAb against IgM led to an important decrease of IgM serum level and internalization of membrane IgM (mIgM) on almost all B cells . Similarly, treatment with a high-avidity anti-IgD antibody induced d isappearance of mIgD on B cells. Treatment with rat MoAb against IgM o r IgD led to a synthesis of specific antibodies and there was a direct relationship between the Ig internalization abilities of rat MoAb and the induction of specific antibody production. Finally, treatment wit h a high-avidity rat MoAb against IgD induced a polyclonal IgE and IgG 1 secretion. The significance of these results on mig receptor functio ns is discussed.