An analysis of host T-cell subsets based on Lyt antigenic markers during the development of spontaneous C3H mammary carcinomas.

Changes in the host T-lymphocyte subsets during the development of spontaneous mammary carcinomas in C3H/HeJ mice were analyzed on the basis of Lyt antigenic markers in retired breeder females prior to and following tumor appearance. Lymphocytes derived from various host lymphoid organs as well as from the tumor site were labeled either directly with 125I-conjugated monoclonal anti-Lyt antibodies or by a sandwich labeling technique with monoclonal anti-Lyt antibodies and 125I-conjugated anti-mouse Ig. The relative incidence of the various Lyt subsets was determined by radioautography. It was found that the overall incidence of T cells within the tumors increased during tumor progression. The incidence of the Lyt-1-, 2+ subset was very high (congruent to 20%) initially within the small, young tumors, and then this incidence declined progressively as the tumor increased in size to 0-5% in older and larger tumors, with a concomitant increase of the Lyt-1+, 2- subset. High levels of Lyt-1-, 2+ lymphocytes were also detected within the thymus (up to 41%) as well as the regional draining nodes (up to 7%) of animals bearing small newly detected tumors and could also occasionally be found in old clinically "tumor-free" control animals. These results support the earlier proposal based on functional studies with primary chemically induced tumors and in hosts bearing transplanted tumors that Lyt-1-, 2+ lymphocytes may play an immunoregulatory role in the early stages of tumor development possibly as facilitators of tumor growth.