A study on tumor infiltrating lymphocytes in mice with spontaneous carcinoma.

Abstract

Differences in immune responses between immunized and non-immunized mice were studied with special reference to tumor-infiltrating lymphocytes (TIL), using inbred WHT/Ht mice with spontaneously developing transplantable squamous cell carcinoma. After inoculating 1×10⁶ tumor cells, a lymphocyte-proliferating response was observed in the spleens and regional lymph nodes of both immunized and non-immunized mice. Histological examination showed marked infiltration of lymphoid cells into tumor tissues of immunized mice, but was much less in non-immunized mice. Lymphocyte subset analysis by a fluorescent antibody method and FACScan indicated that TIL in the immunized mice consisted mostly of surface-Ig⁺, Mac-1⁺ and asialo GM1⁺ cells. This almost completely agreed with the distribution of spleen cells. However, in non-immunized mice, Lyt-1⁺ and L3T4⁺ cells were dominant, differing from the distribution of spleen cells. Furthermore, the killer activity of these TIL and spleen cells against syngeneic tumor cells was studied by ⁵¹Cr release assay. Results showed that TIL and spleen cells of immunized mice had cytolytic, natural killer, and ADCC activities, but none of these could be detected in the non-immunized mice.

The above findings suggest that infiltration of TIL is an expression of immune response of the tumor-bearing host against tumor-rejection antigens. At the site of tumor transplantation in immunized mice various effector cells having anti-tumor activity act toward tumor rejection.