Anti-IFNG monoclonal antibody, clone C250

Acute graft-versus-host disease (aGVHD) hinders the efficacy of allogeneic hematopoietic cell transplantation (HCT). Plasma levels of soluble membrane-bound ST2 (ST2) are elevated in human and murine aGVHD and correlated to type 1 T cells response. ST2 signals through the adapter protein MyD88. The role of MyD88 in T cells during aGVHD has yet to be elucidated. We found that knocking out MyD88 in the donor T cells protected against aGVHD independent of IL-1R and TLR4 signaling in two murine HCT models. This protection was entirely driven by MyD88(-/- )CD4 T cells. Transplanting donor MyD88(-/-) conventional T cells (Tcons) with wild-type (WT) or MyD88(-/-) regulatory T cells (Tregs) lowered aGVHD severity and mortality. Transcriptome analysis of sorted MyD88(-/-) CD4 T cells from the intestine 10 d post-HCT showed lower levels of Il1rl1 (gene of ST2), Ifng, Csf2, Stat5, Batf, and Jak2. Transplanting donor ST2(-/-) Tcons with WT or ST2(-/-) Tregs showed a similar phenotype with what we observed when using donor MyD88(-/-) Tcons. Decreased ST2 was confirmed at the protein level with less secretion of soluble ST2 and more expression of ST2 compared with WT T cells. Our data suggest that Treg suppression from lack of MyD88 signaling in donor Tcons during alloreactivity uses the ST2 but not the IL-1R or TLR4 pathways, and ST2 represents a potential aGVHD therapeutic target sparing Tregs.

Background-A clear understanding of the molecular mechanisms underlying hemodynamic stress-initiated cardiac hypertrophy is important for preventing heart failure. Interferon-gamma (IFN-gamma) has been suggested to play crucial roles in various diseases other than immunological disorders by modulating the expression of myriad genes. However, the involvement of IFN-gamma in the pathogenesis of cardiac hypertrophy still remains unclear. Methods and Results-In order to elucidate the roles of IFN-gamma in pressure overload-induced cardiac pathology, we subjected Balb/c wild-type (WT) or IFN-gamma-deficient (Ifng(-/-)) mice to transverse aortic constriction (TAC). Three weeks after TAC, Ifng(-/-) mice developed more severe cardiac hypertrophy, fibrosis, and dysfunction than WT mice. Bone marrow-derived immune cells including macrophages were a source of IFN-gamma in hearts after TAC. The activation of PI3K/Akt signaling, a key signaling pathway incompensatory hypertrophy, was detected 3days after TAC in the left ventricles of WT mice and was markedly attenuated in Ifng(-/-) mice. The administration of a neutralizing anti-IFN-gamma antibody abrogated PI3K/Akt signal activation in WT mice during compensatory hypertrophy, while that of IFN-gamma activated PI3K/Akt signaling in Ifng(-/-) mice. TAC also induced the phosphorylation of Stat5, but not Stat1 in the left ventricles of WT mice 3 days after TAC. Furthermore, IFN-gamma induced Stat5 and Akt phosphorylation in rat cardiomyocytes cultured under stretch conditions. A Stat5 inhibitor significantly suppressed PI3K/Akt signaling activation in the left ventricles of WT mice, and aggravated pressure overload-induced cardiac hypertrophy. Conclusions-The IFN-gamma/Stat5 axis may be protective against persistent pressure overload-induced cardiac hypertrophy by activating the PI3K/Akt pathway.