Cytokine gene expression by alloactivated cells in SCID mice

Abstract

Objectives: The severe combined immune deficient (SCID) mouse provides a neutral environment to study human immune responses. We therefore tested human gene expression of Interleukin (IL) 2, 4 and 10, interferon gamma (IFNγ); transforming growth factor beta 1 (TGFβ1); and CD40 ligand (CD40L) in splenic extracts of SCID mice after engraftment of PBLs from two persons (direct MLR) or one person plus allopeptides (indirect MLR) in the presence or absence of cyclosporin A (CsA) or FK506. Methods: Cytokine gene expression was detected by RT and quantitative (for IFNγ, TGFβ1 and CD40L) PCR. All cells, allopeptides, CsA (25 mg/kg/day for 7 days) or FK 506 (0.5 mg/kg/day for 7 days) were administered intraperitoneally (IP). Results: In both direct and indirect MLR the numbers of SCID mice expressing the human cytokine genes varied between 33% for IL4 and 100% for IL10, IFNγ, TGFβ1, and CD40L. There was significant interpersonal variation in levels of gene expression. Concomitant CsA or FK506 administration for 7 days did not abrogate early or late (1 week after discontinuation of CsA or FK506) cytokine gene expression in either the direct or indirect MLR, but paradoxically enhanced levels of IFNγ, TGFβ1 and CD40L gene expression in some experiments. Conclusions: The results explain late rejection after rapid calcineurin inhibitor withdrawal or reduction, and illustrate the potential use of SCID mice as a surrogate model to study graft outcome by determination levels of gene expression and sensitivity to immunosuppressive agents in the in vivo alloresponse.