Transfected rat islet tumour cells express mouse major histocompatibility complex class I antigens functionally. Applicable as "pseudo-syngeneic" targets in the multiple low-dose streptozotocin diabetes model.

Rat insulinoma cells clone 5AH-B, were transfected by electroporation with the gene encoding the mouse major histocompatibility complex class I antigen H-2Kb, whereupon stable transfectants were selected and analysed. Data from flow cytometric analyses using three different H-2Kb specific monoclonal antibodies and functional assays using H-2Kb specific alloimmune cytotoxic T cells revealed that the encoded H-2 antigen was expressed in a functional manner. Similar experiments employing the monoclonal antibody OX-18, which recognizes rat major histocompatibility class I molecules, and xenoimmune cytotoxic T cells specific for the endogenously expressed RT1g antigen showed that functional expression of the RT1g antigen was maintained. However, a down-regulation of the expression was observed in H-2Kb positive transfectants, whereas normal expression was retained in Kb negative transfectants. The function of the native promoters of both the endogenous and the transfected class I genes was found to be preserved in the transfectants as assessed by the response to stimulation with interferon-tau. The present study was unable to confirm the reports of RIN specific lysis by T cells from multiple low dose streptozotocin diabetic mice. Even in the presence of the syngeneic restriction element no lysis was observed. We conclude, that rat insulinoma cells clone 5AH-B, are able to integrate a foreign class I antigen gene and express the encoded product functionally. The data also suggest the possibility of creating major histocompatibility antigen positive rat insulinoma cells which are RT1g negative. Such transfectants will be of great potential value for the dissection of cell mediated B cell destructive processes.