Modulation of the immune responses against SRBC after oestriol treatment in mice.

Delayed-type hypersensitivity (DTH), primary direct and indirect PFC, memory antibody response and suppressor cell induction against sheep red blood cells (SRBC) have been examined in oestriol (E3) pretreated mice. The results showed that DTH and primary direct and indirect PFC responses were suppressed by E3 treatment. These suppressive effects could, however, be overcome when oestrogenized mice were given supra-optimal doses of SRBC for each response. On the other hand, the memory antibody response was markedly enhanced when E3 was given prior to the primary antigen stimulation. Induction of the suppressor cells for the antibody response seemed not to be affected by E3 treatment, but the characterization of the suppressor cells revealed that those obtained from E3 treated mice were surface immunoglobulin positive (sIg+) cells whereas those from control mice were not. These results were discussed in terms of the altered antigen distribution due to the activated phagocytic activity of the reticuloendothelial system (RES) after E3 treatment.