T-LYMPHOPENIA IN GENETICALLY-OBESE RATS

Although obese animals are more susceptible to infection, the underlyi ng causes are not fully known. In this study, long-term measurements w ere made of lymphocyte subsets in peripheral blood, spleen, and thymus in genetically obese Zucker (fa/fa) rats. Blastogenic response of spl enocytes to mitogens was also examined. fa/fa rats developed obesity, hyperlipidemia, and hyperinsulinemia after 5 weeks of age. Flow cytome tric analysis revealed that T cells in peripheral blood, spleen, and t hymus were all reduced significantly in obese rats after 8 weeks of ag e compared to nonobese (Fa/-) littermates. All T-cell subsets examined , including CD4(+) and CD8(+) T cells, were similarly reduced in splee n and thymus as well as in peripheral blood with advance in age. In ad dition, proliferative responses of splenocytes to mitogens were signif icantly low in obese rats. These results indicate that long-term obesi ty may reduce the size of the T-cell pool and impair the responsivenes s of splenocytes in rats. (C) 1998 Academic Press.