Environmental regulation of T-cell function in mice: group housing of males affects accessory cell function.

The number of mice housed in a cage was found to exert a major impact on immune function in male mice. Lymph node cells from hen lysozyme (HEL)-primed C57BL/6 male mice, housed in groups of 6/cage or individually, were tested for T-cell proliferative response. Group-housed males showed markedly lower responses than age-matched females. However, in males housed singly for 4-15 weeks, responses were considerably higher, approaching those of female controls. To examine the cellular site of action of the housing effect, the efficiency of splenic antigen-presenting cells (APC) was examined. APC from grouped males were considerably less efficient than APC from females, whereas males housed singly had increased APC function, reaching female levels. Our results demonstrate that environmental manipulation can profoundly modulate cellular immunity, and provide a first mechanistic indication that APC function is a major target for this modulation.