Determinant capture by MHC class II DR3 during processing of mycobacteria leprae 65kD heat shock protein by human B cells

Using T cell immunoblotting we have characterised the immunogenic fragments derived from the Mycobacteria Leprae 65kD heat shock protein that become associated with MHC class II DR3 during processing by a human B cell line. After 5 h incubation with antigen, a peptide of approximately 12kD (approximately 110 amino acids) was the only major fragment found associated with the class II MHC. The association of this oligopeptide was abolished if an excess of a synthetic peptide representing the minimal epitope was included in the culture or when cells were incubated at 4 degrees C. This suggests that the generation of this moiety is dependent on cell metabolism and that its binding to MHC is specific. This large fragment may represent an intermediate in the processing pathway, directly demonstrating the role of MHC in determinant capture during antigen degradation.