Depressed mitogen responsiveness of lymphocytes at skin temperature

The responsiveness of murine lymphocytes and human peripheral blood lymphocytes to phytohemagglutinin, concanavalin A, pokeweed mitogen, and endotoxin was tested in vitro at 32, 35, and 37 degrees C. The responses at 32 degrees C were delayed and often depressed. Mouse cells responded equally well at 35 and 37 degrees C. Human lymphocytes often responded more rapidly at 37 than at 35 degrees C. Since skin temperature, particularly that of the distal extremities, is usually 32 degrees C or less, a relative deficiency in cell-mediated immunity may exist in these sites. This may be part of the reason for the usual localization of certain infections, such as sporotrichosis, to these coller areas.