Observations on rabbit thymocytes and peripheral T cells. I. Anomalous results in the mixed antiglobulin reaction caused by non-specific adsorption of sheep immunoglobulin.

The "single-stage" mixed antiglobulin reaction (MAR) was carried out with rabbit thymocytes. This test involved treating the cells with either sheep or goat anti-rabbit globulin sera, and subsequently reacting them with indicator erythrocytes coated with rabbit immunoglobulin (Ig) so as to form rosettes. An unexpectedly high number (up to 38%) of thymocytes reacted, although the rosettes were weaker than those given by peripheral B lymphocytes. When blood and lymph node lymphocytes or thymus cells which had already been treated with sheep anti-rabbit globulin serum were subsequently exposed to rabbit anti-sheep Ig serum and then rosetted with indicator cells coated with ox Ig (cross-reacts with sheep Ig) almost 100% reaction was obtained in each of the cell suspensions. This was designated the "two-stage" MAR. The anomalous results, both in the one-stage and two-stage MAR, were abolished by pepsin-treating the sheep anti-rabbit globulin serum; thus indicating that sheep Ig is adsorbed non-specifically via the Fc part of the molecules to the surface of rabbit thymocytes and peripheral T lymphocytes.