Preliminary studies of sera from prostatic cancer patients have indicated a reduction in the presence of suppressive ('blocking'?) properties of in vitro parameters of cell mediated immunologic responsiveness induced by a non specific mitogen (phytohaemagglutin) in association with a decrease in the level of α2 globulin and favourable clinical response following cryosurgery. The origin of the immunosuppressive factor(s) migrating on electrophoresis in the α2 globulin fraction of serum remains to be identified. Earlier demonstration of suppression of leucocyte migration by factors elaborated from tumour cells and recent observations of the suppression of lymphocytic reactivity by seminal plasma and coaguloprostatic fluid suggest that suppression and reduction or abrogation of the suppressive properties of serum following cryosurgical destruction of tumour may be attributed to a reduction in soluble prostatic tumour associated antigen shed into the circulation by previously viable tumor. Such antigen while not at a sufficient concentration to engender an immunologic response in the aging and tumour burdened host, may, however, have been sufficient to pre empt the effector limb of cell mediated responsiveness contributing to the observed suppression of lymphocytic reactivity. Cryosurgery, resulting in necrosis and cell death with depletion of the primary source of antigen might thereby have permitted a previously overwhelmed host to respond, viz., the favourable clinical response observed.
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