Antigenic differences between T and B lymphocytes in man

Rabbit antisera against human thymus, spleen, bone marrow or brain were absorbed with various human tissues and tested for their cytotoxic activity on human peripheral blood lymphocytes and thymus cells. Antiserum to brain lost all its activity on thymus cells and lymphocytes following absorption with kidney. A similar absorption of antispleen serum did not reveal antibodies discriminating between thymus cells and lymphocytes. Rabbit antihuman thymus serum (RAHT) absorbed either with kidney or with brain and adult bone marrow had a significantly stronger cytotoxic effect on thymus cells than on lymphocytes. Rabbit antihuman bone marrow serum (RAHBM) absorbed with neonatal brain killed about 30% of lymphocytes or thymus cells. The specificity of absorbed RAHT and RAHBM for the T and B cell subpopulations of lymphocytes, respectively, was established by the following observations: the two antisera showed an additive cytotoxic effect on lymphocytes; RAHT prevented the formation of E rosettes, without affecting the formation EAC' rosettes (RAHBM had the opposite effect), and only RAHT inhibited the mitogenic response of lymphocytes to phytohemagglutinin. It is, therefore, concluded that RAHT absorbed with brain and bone marrow contains antibodies specific for human T lymphocytes, whereas RAHBM absorbed with brain contains antibodies specific for human B lymphocytes.