Identification and partial characterization of surface antigens specific for human normal and leukemic T cells

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Abstract
Rabbit antisera to membrane preparations of human thymocytes (anti‐HTLA), T lymphocytes of the MOLT 4 cell line or B lymphocytes of the LIK cell line, have been serologically characterized and used for the identification of surface membrane antigens specifically expressed by human lymphocyte subpopulations. By immunoprecipitation of surface 125I‐ or NaB (3H)4‐labeled protein followed by sodium dodecyl sulfate polyacrylamide gel electrophoresis of the precipitates, the anti‐HTLA antiserum was shown to detect on thymocytes three glycoproteins of apparent molecular weights 160000, 110000 and 45000. The first two only appeared to be sialylated. A similar pattern of antigens could be detected on cultured T lymphocytes, except for the 45 kDalton glycoprotein which could not be detected on the surface of these cells. None of these proteins were detected on 125I‐labeled Raji cells. The serological specificity of the anti‐MOLT 4 antiserum for T lymphocytes was more restricted since it only precipitated the 160 kDalton antigen. In addition, the 45 kDalton protein was shown to be sensitive to trypsin treatment as was the sheep red blood cell (SRBC) receptor. The results shown suggest a possible activity as SRBC receptor for this particular protein. In contrast, the anti‐LIK antiserum which behaves as an anti‐HLA‐DR reagent in cytotoxicity testing, only precipitates from cultured B lymphocyte lysates the typical Ia‐like 28 and 33 kDalton polypeptides.