Depression of T cell-mediated immunity and enhancement of autoantibody production by natural infection with microorganisms in spontaneously hypertensive rats (SHR).

We studied the effects of breeding conditions on the development of immunological abnormalities in spontaneously hypertensive rats (SHR) with congenital T cell depression. The depression of T cell functions, the production of natural thymocytotoxic autoantibody (NTA), and the development of polyarteritis nodosa were more evident in SHR reared under a conventional (CV) environment than in specific-pathogen-free (SPF) SHR bred in a semi-barrier system. Enhancement of these immunologic abnormalities was also observed by the conventionalization of SPF-SHR. A high frequency of antibodies to mouse hepatitis virus (MHV), Sendai virus, and Mycoplasma pulmonis was detected in CV rat sera, whereas no antibodies were detected in SPF-SHR. The experimental infection of Sendai virus induced the enhancement of T cell depression and of NTA production in SPF-SHR. We interpret these results to mean that the natural infection of microorganisms causes an acceleration of immunologic abnormalities in SHR reared in a CV environment.