In vivo T-lymphocyte response against spontaneous reticulum cell neoplasms in SJL/J mice

The properties of lymphocytes associated with reticulum cell neoplasms (RCN) (type B) occurring spontaneously in SJL/J mice were examined. The activity of 20 alpha-hydroxysteroid dehydrogenase (20 alpha-SDH) was used as a marker for activated T-cells. High levels of this enzyme were found in cell suspensions of tumors taken from 6- to 7-month-old mice. Treatment of the cells derived from tumorous organs with anti-theta serum and complement resulted in a loss of the 20 alpha-SDH activity; this indicated that T-lymphocytes populate the RCN. The activated T-cells in the neoplastic tissue were larger than small lymphocytes. In the more advanced stage of tumor growth seen in 1-year-old mice, the percentage of malignant reticulum cells was low and the neoplastic tissue showed low levels of 20 alpha-SDH activity. Tumor cells irradiated in vitro triggered syngeneic lymphocytes to proliferate in tumor-lymphocyte mixed cultures. The T-cell proliferative response measured by [3H]thymidine incorporation was accompanied by a marked increase in 20 alpha-SDH activity. The spleen cells taken from mice bearing old tumors that showed marked fibrosis did not respond to T- and B-cell mitogens. Histologically, the structure of the spleen was preserved, with few or no tumor cells. Spleen cells from age-matched healthy mice responded to mitogens.