Immunophenotype of small cell lung carcinoma. Expression of NKH-1 and transferrin receptor and absence of most myeloid antigens.

NKH-1 is a monoclonal antibody that reacts with human natural killer (NK) cells and neural tissue. Because other monoclonal antibodies reacting with NK cells have been found on small cell lung carcinoma (SCLC), frozen tissue sections of 22 lung tumors including nine SCLC, two bronchial carcinoids, and 11 non-SCLC were tested for the presence of NKH-1 antigen by a sensitive alkaline phosphatase/anti-alkaline phosphatase technique. The labeling reactions of NKH-1 in frozen tissue sections were compared with reactions of a panel of 21 other monoclonal antibodies against NK cells, leukocyte antigens, cytokeratins, or nonlineage specific antigens. The antibody NKH-1 reacted strongly and diffusely with all of the SCLC and bronchial carcinoids but with none of the non-SCLC. NKH-1 also strongly labeled peripheral nerves in tissues adjacent to tumor. Two antibodies to cytokeratins reacted with all of the tumors and outlined tumor cells well, distinguishing them from surrounding stromal cells and leukocytes. OKT9, an antibody against transferrin receptor labeled all SCLC and eight of 11 non-SCLC but did not react with bronchial carcinoid. The antibodies Leu-M1, OKT10, Leu-7, and My4 reacted with 67%, 33%, 22%, and 11%, respectively, of the SCLC tested. The remaining 14 antibodies, including several with leukocyte specificity, labeled neither SCLC nor bronchial carcinoid. Thus, SCLC has a distinct immunophenotype (NKH-1 positive, keratin positive, and transferrin receptor positive), which may be helpful distinguishing this tumor from other tumors of lung including non-SCLC. SCLC infrequently expresses other leukocyte-associated antigens.