[A study on the location of immuno-suppressive factor(s) in restraint rats and mice]

A serum lymphocyte-proliferation suppressive factor(s) induced by restraint stress over 10 h was found in previous studies in both rats and mice. The present study was undertaken to investigate the sites of its production. The results show that large doses of irradiation and cyclophosphamide (CY) decreased the total number of splenic nucleated cells, but the production of the suppressive factor was inhibited only by irradiation. This indicates that the drop in total number of lymphocytes does not play any key role in the production of the serum suppressive factor. Cell classification showed that the ratio of T to B cell was decreased by radiation but increased by CY, suggesting that this ratio may be relevant to the production of the factor. Inhibition of the production was also observed in nude mouse (an animal showing a lack of T cell activity), again supporting that T cells are involved in the production of the inhibitory factor.