Background: Tyrphostin AG490 (AG490) potently and selectively inhibits gammac/Janus kinase 3-dependent signaling pathways, including downstream Stat5a/b activation and subsequent T cell proliferation by alloantigen stimulation. We evaluated the effects of AG490 on acute rat lung allograft rejection.
Methods: A 7-day course of an intraperitoneal (IP) injection with 10 mg/kg, 15 mg/kg, or 20 mg/kg AG490 was administered to inhibit the rejection of orthotopically transplanted Brown Norway (RT1n) rat lung allografts in Fischer 344 (RT1(1vl)) rat recipients. The progression of allograft rejection was evaluated by X-ray with a semi-quantitative scoring system and was evaluated histologically with a semi-quantitative rejection scoring system for acute lung allograft rejection. Moreover, to determine whether AG490 regulates CD4+ T cell differentiation during acute rejection, flow cytometry was used to investigate Th1 (interferon-gamma) and Th2 (interleukin [IL]-4, IL-10) intracellular cytokine profiles and the CD4+CD25+ T cell population in recipient splenocytes.
Results: Results of radiology and histology confirmed that treatment with AG490 significantly suppressed acute lung allograft rejection. Furthermore, the splenocytes of the AG490-treated recipients had significantly lower production of interferon-gamma and relatively higher production of IL-10, implying that a Th2 shift was induced by AG490. In addition, AG490-treated recipients had a significantly increased population of CD4+CD25+ T cells in their splenocytes on Day 6 after transplantation.
Conclusion: These findings suggest that treatment with AG490 prevents acute lung allograft rejection in rats. The effects of AG490 may contribute to development of CD4+CD25+ T cells and a Th2 shift of CD4+ T cells.