DYNAMICS OF THE CYTOKINE MESSENGER RNA EXPRESSION PATTERN IN THE LIVER OF BABOONS INFECTED WITH SCHISTOSOMA MANSONI

Periovular granulomas are the major lesions in baboons infected with Schistosoma mansoni. Temporal Northern blot analysis of cytokine messenger RNA (mRNA) expression in granulomatous baboon livers demonstrated tissue-specific expression. Interleukin 1 beta (IL-1β), IL-6, tumor necrosis factor alpha, and migration inhibitory factor (MIF) mRNAs were expressed strongly at week 6 of infection and decayed thereafter, whereas interferon gamma (IFN-γ), IL-2, IL-10, and IL-12 mRNAs were first expressed at week 12, with IFN-γ and IL-12 mRNA expression persisting until week 17. IL-4 and IL-5 mRNAs first appeared at week 12, with IL-4 persisting unchanged and IL-5 increasing by week 17. Thus, egg deposition induced strong hepatic expression of proinflammatory and downregulatory cytokines. The cooccurrence of IL-2, IFN-γ, IL-4, and IL-5 mRNAs at week 12 confirms that baboons, like humans, show a mixed type 1–type 2 cytokine response. When granulomas had become smaller at 17 wk, IFN-γ, IL-4, and IL-5 were the only cytokine mRNAs that were expressed strongly, implicating them in granuloma modulation. The early expression of MIF mRNA and MIF's role as the main counterregulator of glucocorticoid immunosuppression ties in with our earlier demonstrations of circulating adrenal steroids changing with the progression of schistosomiasis in baboons and of proinflammatory cytokine mRNA expression in the hypothalamic–pituitary–adrenal axis tissues of infected baboons. Together, these data imply neuroendocrinological influences on disease progression in schistosomiasis.