Effect of ambient temperature on immune functions of athymic nude mice.

We performed cytoflourometric analysis of the expression of various T and B surface markers on lymphocytes isolated from bone marrow, spleen and lymph nodes of nu/nu and +/+ mice kept at 22 or 28 degrees C for various time intervals. In bone marrow of nu/nu mice the cold exposure decreased the expression of sIg and CD4 molecules and increased expression of MHC class II antigens. In the spleen, the numbers of MHC class II and sIg expressing lymphocytes continually decreased with the length of cold exposure. At the same time, the number of CD4+ cells increased. The most pronounced changes in lymph nodes were observed in the expression of CD5 antigen. The values obtained from euthymic mice kept at cold temperature were always comparable to those found in mice kept at 28 degrees C. Exposure to lowered temperature caused in nu/nu mice also significant changes in appearance of subpopulations of cells differing in size and in density of antigens. The changes did not affect the antibody response to a thymus-independent antigen.