Analysis of a Sheep Anti-pig T Lymphoblast Serum with Specificity for E Rosette-forming Lymphocytes

Sheep antibodies against a pig E-rosette-forming lymphoblastic T lymphoma raised by two intravenous injections of 10(10) cells showed little lymphocytotoxic activity which could be absorbed with red cells, alveolar macrophages or kidney or liver cell homogenates. Bone marrow absorption yielded subpopulation specific antibody which binds to E rosette-forming cells (E.RFC) using either complement-mediated cytotoxicity or indirect antiglobulin rosette formation. In 30 blood lymphocyte preparations from 20 pigs with a range of approximately 20-85% E rosettes the mean E% 43.5 +/- 2.7 agreed with the % antigen+ cells by cytotoxicity mean = 42.6 +/- 2.7 and in each individual sample these figures also agreed closely. In samples of blood lymphocytes enriched and depleted for E rosettes, results of %E+ also agreed closely with % antigen+ cells. This relationship also held for thymocytes and the specific antibodies could be completely absorbed with thymocytes. These data show that the antibody identified peripheral and thymic E.RFC. Bound to lymphocytes the antibody inhibited E rosette-formation with sheep red blood cells (SRBC) in saline (S) and dextran (DS) and with pig RBC in dextran and in Ficoll, but did not affect B cells shown by immunofluorescence, direct antiglobulin rosette formation or Fc rosette-formation, either in saline or dextran, (which include T gamma cells). E rosette inhibition was dependent on antibody concentration, showing single and double sigmoid curves for S and DS rosettes respectively, consistent with differing ease of inhibition of the strong and weak rosette formation. The same spectrum of inhibition of rosette formation by antibody binding followed subsequent incubation with C'6-deficient rabbit serum, but with C'-sufficient serum resulted in loss of cells which require dextran for Fc rosette-formation (T gamma). Thus the serum reveals E rosette-forming T cells and their subpopulations, perhaps by binding to the SRBC receptor.