Characterization of a human T cell line reactive to a 52 kDa islet protein

A 52 kDa islet protein has recently been identified as the target of autoantibodies in the NOD mouse model of IDDM and humans with IDDM. However, the presence of T cell immunity against the 52 kDa islet protein in IDDM has not been reported. We report the establishment and characterization of a T cell line (19KW) that reacts to purified 52 kDa islet protein (purified p52) from a subject with IDDM. The purified p52 induced a proliferative response as measured by thymidine incorporation in the 19KW T cell line with a stimulating index of up to 48. The proliferative responses were greater with increasing doses of purified p52 (0.1, 0.5, 2.0, and 6.0 μg/well). No reactivity was found to a liver fraction purified in the same manner as 52 kDa protein, BSA, ovalbumin extracts of rat muscle, fibroblast, adrenal, or pituitary tissue and to a rat exocrine cell tumor. Irradiated PBMC were required as antigen presenting cells (APC) for 19KW reactivity to the purified p52. The addition of anti-HLA DR or anti-HLA DQ antibodies significantly decreased the islet antigen-induced proliferative response. The addition of antibodies to HLA DP and class I MHC had no effect. Flow cytometric analysis revealed that the majority of T cells expressed CD4 and CD45RO molecules. T cell receptors Vβ6 and Vβ5.1 were found on 30 and 14% of the CD3⁺ (T cells) 19KW cells, respectively. In conclusion, a purified p52-reactive human T cell line predominantly consisting of TCR Vβ6⁺ and Vβ5.1⁺ cells has been established from a subject with IDDM. Reactivity to the purified p52 is antigen dose-dependent, tissue specific, requires irradiated PBMC as antigen presenting cells, and is HLA DR- and HLA DQ- restricted T cell lines specifically reactive to p52 may be useful for investigating further the role of this antigen in the pathogenesis of IDDM.