INDUCTION OF B-CELL AND T-CELL TOLERANCE IN-VIVO BY ANTI-CD23 MAB

T cell tolerance can be induced by B cell presentation of Ags to naive T cells. To further characterize this mechanism of T cell tolerance i nduction, we have investigated the effects of injecting mice with an i ntact rat IgC2a Ab, which binds to the B cell low-affinity Fc epsilon receptor (CD23), on the responsiveness of B cells and T cells to rat I gG2a. Our observations indicate that 1) intravenous, subcutaneous, or intraperitoneal injection of this Ab induces antigen-specific B cell a nd T cell tolerance; 2) both forms of tolerance are induced more compl etely by injection of rat IgC2a anti-CD23 mAb than by injection of an equal dose of a control rat IgG2a Ig; and 3) reduced responsiveness to Ag is seen as early as 1 to 3 days after anti-CD23 mAb injection and reaches maximum levels by 7 days after injection. Although tolerance i nduced by the injection of soluble proteins has been reported to be ch aracterized by reduced production of IL-2 and IFN-gamma, but normal pr oduction of IL-4, injection of mice with rat IgG2a anti-mouse CD23 mAb greatly decreases the IL-4 response to a rat IgG2a immunogen that nor mally induces a large IL-4 response.