Stimulation and suppression of rat mast cell functions by alloantibodies.

The stimulatory as well as the inhibitory capacity of alloantisera has been investigated with respect to rat mast cell functions. Alloantibody against alloantigens coded for by the major histocompatibility (H-1) gene region promoted histamine release from purified LEW mast cells. This process was found to be complement-independent but demonstrated an absolute requirement for calcium. Pretreatment of mast cells with anti-H-1 antisera in the absence of calcium markedly suppressed the IgE-dependent histamine release challenged either by antigen or by anti-IgE antibody. The alloantisera, however, did not interfere with the ability of compound 48/80-associated histamine liberation. Additionally, antibodies specific for H-1 antigens were highly effective in inhibiting the binding of IgE to the mast cell surface. Alloantisera absorbed with erythrocytes lost their capacity to block mast cell functions. Based on these data the possible ralationship between H-1 alloantigens and the IgE receptor on the mast cell surface is discussed.