A mitochondrial fraction isolated from bovine heart tissue was prepared as described previously (Fregeau et al., 1990) ; native PDC-E2 was thence purified (Stanley and Perham, 1980) . As a negative control, a-casein, was purchased from Sigma Inc. (St Louis, MO). A lipoated, huPDC-E2 peptide (p163) spanning amino acids 163-176 (GDLLAEIETDKATI), previously shown to be a major T cell epitope (6 -8), was synthesized by Alpha Diagnostic International (San Antonio, TX). Peptide purity was confirmed by reversed phase HPLC.