Characteristics of xenograft rejection. I. Augmented cytotoxicity of peritoneal T cells after intraperitoneal injection of booster antigen and/or proteose peptone.

Cytotoxic activity was detected by the 51 CR-release test in peritoneal exudate (PE) cells of mice immunized with rat lymphocytes 5 days previously, but not in their spleen or lymph node cells. This activity appeared to be exerted by cytotoxic T cells, which had the same characteristics as those for allogeneic systems in respect to antigen specificity and time course. An intraperitoneal booster with rat lymphocytes 2 days before the assay effectively enhanced the cytotoxic activity of PE cells. When mice were immunized with rat lymphocytes subcutaneously or intravenously, cytotoxic activity was scarcely detected in PE cells. However, significant activity was detected in PE cells when the immunized mice were injected intraperitoneally with proteose peptone 2 days before the assay.