Human myeloid differentiation antigens identified by monoclonal antibodies to the myelomonocytic leukemia cell line RC-2A

Murine monoclonal antibodies to human myeloid cell surface differentiation antigens were prepared using the myelomonocytic leukemia cell line RC-2A as immunogen. Using a highly sensitive colorimetric assay, antibodies were selected as myeloid-associated based on their binding to RC-2A cells, but not to cells of the autologous EBV-transformed* B cell line Cess-B. Antibodies to five distinct cell surface antigens were extensively characterized for their binding to normal and leukemic hemopoietic cells, and to tissue sections. Three antibodies may identify antigens previously described in the International Leucocyte Typing Workshops (CD14, CD11b and CD31). The other two antigens appear to be expressed at low levels on the surface of RC-2A cells, and do not correspond to existing CD groups. One of these is also present on monocytes and neutrophils. Both were present on myeloid progenitor cells, as judged by depletion experiments with antibody and complement, although neither bound appreciably to myeloid leukemic cells as judged by indirect immunofluorescence. The other three antibodies bound preferentially to leukemic specimens displaying monocytic differentiation. Four of the antibodies could be demonstrated to bind to cells in frozen sections of tonsil and small intestine and all gave distinct patterns of reactivity. In particular, these antibodies differed markedly in their binding to endothelium, follicular dendritic cells and various types of tissue macrophages. These antibodies may be useful in the study of the differentiation of myeloid cells and in studies of immunologically mediated disease such as allograft rejection.