A novel monoclonal antibody (OPD4) recognizing a helper/inducer T cell subset. Its application to paraffin-embedded tissues.

A novel monoclonal antibody (MAb), OPD4, reactive with a helper/inducer (H/I) subset of T cells in formalin-fixed, paraffin-embedded tissue sections, has been identified through immunization with an activated H/I T cell line, namely DL40. The antibody is an IgG1 antibody and it recognizes an antigen with a molecular weight of 200 kd, corresponding to that of leukocyte common antigen. OPD4+/CD4+ T cells provided better help for pokeweed mitogen-stimulated polyclonal IgG production than OPD4-/CD4+ T cells. OPD4 recognized the H/I T cell subset even in paraffin-embedded tissue sections, but did not recognize nonhematopoietic cells, suppressor/cytotoxic T cells, B cells, monocytes in the peripheral blood, or other normal hematopoietic cells as examined by the flow cytometric and immunoperoxidase methods. Besides the lymphoid cells, OPD4 reacted with a number of histiocytes (epithelioid cells) in tissues from sarcoidosis and tuberculosis. For the neoplastic lesions, OPD4 reacted with approximately half of the cases of T cell lymphomas. Consequently, OPD4 may be useful for the diagnosis and study of malignant lymphomas and other related lesions.