TGF-beta Shield

Administration of donor-derived immature dendritic cells (DC) treated with transforming growth factor-beta (TGF-beta) to prevent allograft rejection is not applicable for clinical use. We therefore attempted to explore the use of recipient-derived DC pulsed with donor antigens via the indirect pathway (cross-priming). DC were propagated from C3H (H2(k)) bone marrow (BM) using granulocyte-macrophage colony stimulating factor (GM-CSF) and interleukin-4 (IL-4). TGF-beta (0.2 ng/mL) was added at the initiation of culture. The resultant TGF-beta DC were pulsed with B10 (H2(b)) splenocyte lysate. Expression of major histocompatibility complex (MHC) class I and II was not affected, while CD40, CD80, and CD86 costimulatory molecules on DC were significantly inhibited by treatment with TGF-beta. C3H DC pulsed with B10 antigens stimulated a proliferative response in C3H T cells which was inhibited when DC were treated with TGF-beta, and the cytotoxic T-lymphocyte (CTL) activity was also inhibited. This observation correlated with reduced interferon-gamma (IFN-gamma) and increased IL-10 production. A single injection of TGF-beta DC prolonged allograft survival (median survival time [MST] 18 days vs 10 days in no-DC treatment control; P < .05). These data indicated that an approach utilizing recipient DC as a "vaccine" strategy is possible.

The suppressor activity of splenic macrophages induced by Mycobacterium intracellulare infection (MI-M phi s) against T cell concanavalin A (Con A) mitogenesis is mediated by MI-M phi's mediators, such as reactive nitrogen intermediates (RNIs), phosphatidylserine, free fatty acids, prostaglandin E(2) and to a minor extent TGF-beta. Here, we have compared the roles of RNIs and TGF-beta in the expression of MI-M phi's suppressor activity against Con A mitogenesis and anti-CD3 monoclonal antibody (mAb)- and anti-CD28 mAb-induced mitogenesis (TCR signal-induced mitogenesis) of the target T cells, and have found the following. First, N(G)-monomethyl-L-arginine (NMMA) inhibited MI-M phi's suppressor activity against TCR signal-induced mitogenesis as well as Con A mitogenesis. Second, anti-TGF-beta mAb weakly restored the MI-M phi-mediated suppression only in the case of Con A mitogenesis, under limited conditions, such as very low cell densities of MI-M phi s. Third, the blocking effects of NMMA plus anti-TGF-beta mAb were somewhat more prominent in the case of Con A mitogenesis than in the case of TCR signal-induced mitogenesis. Fourth, Con A- or TCR signal-stimulated MI-M phi s secreted significant amounts of the latent TGF-beta but not the active one. These findings indicate that RNIs, but not TGF-beta, play important roles in the MI-M phi-mediated suppression of TCR signal-induced mitogenesis, as well as Con A mitogenesis, of the target T cells.