[Time effect of restraint stress-induced suppression of lymphocyte transformation]

In the present study, restraint, which caused no direct tissue damage, was selected as a method of stress to investigate time effect of stress-induced suppression of lymphocyte transformation in rats. The lymph node and spleen extract or the serum from rats restrained for 3, 6, 12, 18 h or 12, 24, 48, 72, 96 h after restraint, with concanavalin A (Con A), was added to the lymphocyte suspension of rat mesenteric lymph node and was incubated for 72 h. The optical density (OD) value indicating the level of lymphocyte transformation was determined by colorimetric assay of methylthiazol tetrazolium bromide (MTT). The results are as follows. (1) The lymph node and spleen extract or the serum from the rats restrained for 3 or 6 h did not markedly affect the lymphocyte transformation. (2) The lymph node and spleen extract or the serum from the rats restrained for 12 h or 18 h significantly inhibited the lymphocyte transformation and stronger inhibition occurred at 18 h. (3) Up to 96 h after restraint, the suppressive effect of the lymph node or spleen extract on the lymphocyte transformation still existed, but the suppression of the serum on the lymphocyte transformation almost disappeared. These results suggest that the restraint of rats may cause lymphoid tissues to produce some immune suppressive protein of stress, which is released into blood leading to a generalized suppression of cellular immunity.