ANTIGEN-PROCESSING AND PRESENTATION OF A NATURALLY GLYCOSYLATED PROTEIN ELICITS MAJOR HISTOCOMPATIBILITY COMPLEX CLASS II-RESTRICTED, CARBOHYDRATE-SPECIFIC T-CELLS

It is well known that T cells recognize antigen as processed peptides bound to major histocompatibility complex molecules on the surface of antigen-presenting cells. Recently, it has been shown that T cells can specifically recognize synthetic glycopeptides. However, whether glyc opeptides are selected for presentation during antigen processing of g lycoproteins and eventually elicit carbohydrate-specific T cells is st ill an open question. In this study, we utilized synthetic glycopeptid es to analyze T cell recognition of the naturally glycosylated immunod ominant peptide representing type II collagen (CII) residues 256-270. In this peptide, lysines at positions 264 and 270 may be posttranslati onally modified by hydroxylation and subsequent O-linked glycosylation with beta-galactosyl or alpha-glucosyl-(1 --> 2)-beta-galactosyl resi dues. T cell hybridomas established from type II collagen-immunized mi ce specifically recognized CII 256-270 with either galactose or glucos yl-galactose at position 264. The T cell hybridoma recognizing glucosy l-galactose displayed no cross-reactivity either to galactose cr to th e structurally different alpha-galactosyl-(1 --> 4)-beta-galactose. Fu rthermore, the T cell hybridoma recognizing-galactose did not cross-re act to glucosyl-galactose or galactosyl-galactose, indicating that the antigen-presenting cells (bulk spleen cells, lipopolysaccharide-stimu lated spleen cells, anti-CD40-stimulated spleen cells, peritoneal exud ate cells or CFA-primed lymph node cells) inefficiently processed carb ohydrates when the antigen was given as a glycopeptide.