A monoclonal antibody against a surface antigen shared by human large granular lymphocytes and granulocytes

A monoclonal IgM antibody VEP13 was raised against a cell membrane antigen by immunizing BALB/c mice with a cell preparation enriched for human large granular lymphocytes (LGL). These cells are known to include the effector cells responsible for natural killer (NK) and killer (K) cell activity. By indirect immunofluorescence, VEP13 antibody reacted with 21.4 +/- 7.9% of peripheral blood lymphocytes (PBL) and more than 95% granulocytes but not with B lymphocytes, monocytes, erythrocytes, thrombocytes, thymocytes, and immature bone marrow cells. Cell suspensions enriched for T cells by means of E-rosetting using neuraminidase-treated sheep red blood cells contained 14.7 +/- 5.5% of VEP13+ cells. When PBL were treated with VEP13 antibody and complement, NK activity against a variety of target cells was greatly reduced and K cell activity was also strongly affected. Enrichment experiments of VEP13+ cells by means of the fluorescence-activated cell sorter revealed that all the NK activity resides in the VEP13+ fraction. This cell fraction was a homogeneous population of LGL. Studying the coexpression of various other antigens as defined by monoclonal antibodies, 84.6 +/- 4.6% of VEP13+ cells also expressed M1, 81.6 +/- 5.5% T10, 47.9 +/- 14.4% Leu 2a, 51.6 +/- 17.0% human Lyt-3, and 6.0 +/- 4.0% HLA-DR antigens. Leu 1, Leu 3a, and T6 antigens were found to be absent from VEP13+ cells. We conclude that VEP13 antibody should be helpful in determining LGL in peripheral blood as well as in tissue sections of tumor patients.