The effect of xenoantisera on T-lymphocyte functions in the absence of complement

An attempt was made to determine whether xenoantisera can detect functional receptors on mouse T lymphocytes. Antisera were raised by immunizing rabbits with BALB/c thymus cells, boiled thymus homogenate, brain homogenate or bone marrow cells. Following heat inactivation these antisera were absorbed with mouse kidney and liver homogenates, and studied for their effect, in the absence of C', on the activity of murine T lymphocytes. Rabbit anti-bone marrow serum (RAB) had no effect on the mixed lymphocyte reaction (MLR) nor on cell-mediated lysis (CML). In contrast, rabbit anti-thymus serum (RAT) and anti-boiled thymus serum (RABT) inhibited strikingly, the MLR, CML, and the response to concanavalin A and phytohemagglutinin. Rabbit anti-brain serum (RABR) caused a marked increase of the proliferation of lymphocytes both in the presence or absence of various stimuli and had no effect on the CML. Absorption experiments indicated that a number of antigens are involved in the inhibitory activity of RAT. Antibodies to a T cell specific antigen interfere with the response of T lymphocytes to mitogenic stimuli, while the activity of cytotoxic T cells is inhibited by antibodies to a determinant shared by B and T lymphocytes.