DIRECT IDENTIFICATION OF NATURALLY PROCESSED AUTOANTIGEN-DERIVED PEPTIDES BOUND TO HLA-DR15

Biochemical analysis of HLA class II-associated peptides from antigen pulsed cells is a potentially useful approach to the analysis of antig en processing and presentation because it examines directly which anti gen-derived peptides are presented. This is especially advantageous in the analysis of self-antigen presentation where conventional approach es utilizing antigen-specific T cells may be biased by the presence of self-tolerance, However, successful biochemical analysis has been rep orted for only one exogenous antigen and no autoantigens. We have used a novel analytical approach coupling biochemical data with the report ed properties of class II-associated peptides to characterize the pept ides derived from a clinically relevant autoantigen presented on the d isease-associated class II type. Incubating the target of autoimmune a ttack in patients with Goodpasture's disease, the 230-amino acid NC1 d omain of the alpha 3 chain of type IV collagen (Goodpasture antigen, a lpha 3(IV)NC1), with human B cells homozygous for HLA-DR15, the allele carried by 80% of patients, we find that alpha 3(IV)NC1 is presented as at least two sets of three to five peptides centered on common core sequences (nested sets). Synthetic peptides containing these core seq uences bind to HLA-DR15 with intermediate affinity (IC50, 1.1-6 mu m).