The local cell response to human lung carcinomas

Non-malignant inflammatory cells were studied in tissue sections and cell suspensions from 21 human lung carcinomas. The different cell types were identified and quantified by means of histochemical and immunohistochemical methods. All tumours were surrounded and to a lesser degree also infiltrated by lymphocytes, macrophages, plasma cells containing IgG, IgA, or IgM, and a small number of mast cells. No evident signs of cell necrosis were present in association with these mononuclear cell infiltrates. Central tumour necroses were dominated by large numbers of neutrophils and macrophages, a reaction considered to be secondary to ischemic necroses in rapidly expanding tumours. The weakest mononuclear cell infiltrates were found in tumours with extensive necrotic areas. Of the tumour lymphocytes 3-67% (mean 37%) were T-lymphocytes, 4-32% (mean 19%) were B-lymphocytes. The relation between these markers did not always correlate with the findings in peripheral blood: low percentages of T-lymphocytes were found in some tumours even when the percentage of T-lymphocytes in peripheral blood was within the normal range. The demonstration of both T-lymphocytes and macrophages in and around the tumour tissue may reflect a local immune response against the neoplastic cells, while the presence of plasma cells in all tumours supports the theory that the tumour also induces a local production of immunoglobulin which may interfere with the cellular immunity.