T-splenocytes from non-obese diabetic mice binding to xenogeneic pancreatic beta-cells in vitro. Implication of the alpha/beta T-cell receptor and of major histocompatibility complex class II molecules from target cells

Abstract

As compared to several strains of control mice, NOD mice displayed an increased number (P < 10(-4)) of splenocytes binding in vitro to xenogeneic rat RIN cells or hamster HIT cells, but not to nine non-beta cell lines. The increased binding to RIN cells was abolished by competition with RIN membrane extracts. It was prevented by depletion of Thy 1-2+ splenocytes, and by blocking the T-cell receptor (TCR) complex with anti-CD3 MoAbs, anti-alpha/beta TCR MoAbs, or their F(ab)'2 fragments (P < 10(-3)), but not with anti-gamma/delta TCR MoAbs. Neither anti-V beta 8 nor anti-V beta 6 MoAbs modified the signal. MoAbs against rat MHC class II molecules, but not MoAbs against rat class I molecules, inhibited the increased RIN-adhesion of NOD splenocytes (P < 10(-3)). After 3 h or 8 h of co-incubation, the number of RIN-binding splenocytes was not different between NOD and control mice, and class II molecules were undetectable on RIN cells. Class II+ RIN cells appeared after 20 h of coculture when the increased binding was also observed. When 10,000 rad-irradiated RIN cells were used for the co-incubations, neither class II+ RIN cells nor the increased binding of NOD splenocytes were found. As revealed by immunofluorescence, MoAbs against rat class II molecules cross-reacted with 30% of NOD (but not of control) splenocytes. Conversely, anti-NOD class II MoAbs (but not MoAbs against non-NOD class II molecules) cross-reacted with 20% of RIN cells coincubated with splenocytes. Thus, despite the species barrier, T-splenocytes from NOD mice display an increased adhesion to xenogeneic beta-cells. This binding involves T splenocytes bearing alpha/beta TCRs and RIN cells induced to express MHC class II molecules. MHC restriction may be completely absent in this phenomenon. Alternatively, the rat class II products may be directly recognized by NOD T cells in a xenograft context, and this model may therefore be useful toward the comprehension of some mechanisms leading to the rejection of islet xenotransplants. Finally, because of a cross-reaction with I-Anod, these rat Class II molecules may also either be directly recognized by I-A autoreactive NOD T cells or present RIN peptides to NOD alpha/beta TCRs, and thus would be relevant to the debated ability of beta cells to function as antigen-presenting cells.