Further evidence on lymphocyte resistance of tumor-bearing in vitro rats to phytohemagglutinin.

A study was made of the survival of peripheral blood lymphocytes in short-term cultures with a standard dose of phytohemagglutinin (PHA) in rats during the course of methylcholanthrene (MC)-induced carcinogenesis. Peripheral blood lymphocytes of (BDXLW)F1 hybrid rats were tested at various time intervals following MC application. The investigation involved a group of rats in which tumors had not appeared as yet after MC application, a further group with developed tumors of varying sizes, and a third group in which the tumors were extirpated, their peripheral blood lymphocytes being examined both before and at a definite time interval after the extirpation. Finally, another group of animals was investigated in which no tumor appeared up to 14 months after MC administration. The higher survival values of lymphocytes in PHA cultures in animals with primary MC-induced tumors in comparison with those of the control animals were found to be related to the presence of a progressing tumor. The results are discussed in terms of a possible change of T and B lymphocyte ratio in the peripheral blood in the presence of a tumor antigen.