Inhibition of in vitro immune responses by antisera to H-2 or Ir gene products.

Heat aggregated IgG and antisera reacting with Ir-1 products (Ia antigens) inhibited the in vitro primary responses of mouse spleen cells to SRBC by 50-90% and depressed EA but not EAC rosette formation by 70-90%. These experiments suggest that alloantisera to the H-2 complex express at least part of their inhibitory properties by blocking the Fc receptor on B cells, and the data support the concept that certain Ia antigens and the Fc receptor are identical or closely associated. In addition, these studies showed that the immune response may be inhibited by antisera that react with H-2K and H-2D gene products.