Surface-bound Immunoglobulin as a Marker of B Lymphocytes in Man

IMMUNOLOGICAL reactions in many species depend on two functionally different types of small lymphocytes, thymus-derived T lymphocytes and bone marrow-derived B lymphocytes¹. In the mouse, the θ antigen is a marker for T lymphocytes, while membrane-bound Ig is found on θ-negative lymphocytes². This has raised the question whether the presence of surface-bound Ig³ may be regarded as a marker for B lymphocytes. We have obtained data indicating that this is the case with human lymphocytes.