Influence of change from grouped to individual housing on a T-cell-dependent immune response in mice: antagonism by diazepam.

Transferring CD-1 mice from grouped to individual housing and then maintaining them individually resulted in a decline in the peak IgM plaque-forming cell (PFC) response to sheep red blood cells (SRBCs). However, the immunosuppression was dependent on the amount of time mice were maintained individually. In particular, individual housing for 5-10 days prior to SRBC inoculation and for 4 days following inoculation resulted in a suppression of the splenic PFC response and serum antibody titers. Shorter periods of individual housing (4 days following inoculation) did not provoke the immunosuppression. Likewise, following more protracted individual housing (15-30 days prior to inoculation) the immunosuppression was not evident. Inasmuch as daily treatment with an anxiolytic, diazepam (1.0 mg/kg), antagonized the suppression induced by 5 days of individual housing, it was suggested that the change from group to individual housing and then maintenance of animals individually acted much like a stressor to induce the immunosuppression.