Immunology of ocular tumours.

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Distinct roles for transforming growth factor-β2 and tumour necrosis factor-α in immune deviation elicited by hapten-derivatized antigen-presenting cells

The role of antigen-presenting cells (APC) in the induction of antigen-specific unresponsiveness was examined, using two functionally distinct murine macrophage hybridomas, #59 and #63 cells. Derivatized with the hapten (dinitrofluorobenzene; DNFB), #59 cells induced contact hypersensitivity (CH) in mice. Hapten-derivatized #63 cells failed to induce CH. Instead, they prevented recipients from acquiring CH when exposed subsequently to a sensitizing dose of the hapten. Similarly, hapten-derivatized #59 cells, pretreated in vitro with transforming growth factor-β2 (TGF-β2) lost their capacity to evoke CH, and induced tolerance. Hapten-derivatized #63 cells and TGF-β2-treated #59 cells eliminated CH in mice sensitized to hapten. Reverse transcription–polymerase chain reaction analysis of mRNAs for various accessory molecules important in T-cell activation revealed that #63 and TGF-β2-treated #59 cells differed only in their expression of tumour necrosis factor-α (TNF-α) mRNA. The latter expressed higher levels of TNF-α mRNA than did untreated #59 cells. As a consequence, #63 and TGF-β2-treated #59 cells, both of which induce tolerance, secrete TNF-α protein unlike untreated #59 cells, which do not induce tolerance to hapten. Since neutralizing anti-TNF-α antibodies abrogated the tolerogenic potential of #63 cells in vivo, we conclude that TGF-β2 equips hapten-bearing APC with the capacity to evoke systemic immune deviation in which CH is selectively silenced. We speculate that one effect of TGF-β2 is to cause APC to up-regulate TNF-α production. In turn, this cytokine biases the functional property of responding hapten-specific T cells in a direction that not only interferes with acquisition, but suppresses induction of CH