T-cell recognition of an allogeneic RT1-Dbu class II MHC peptide

The allo-antibody response of several rat strains to an unconjugated synthetic 20 amino acid peptide derived from the alpha helical region of the RT1-Du beta chain was tested. The LEW (RT1l) and WAG (RT1u) strains produced little or no antibody; the PVG (RT1c) and DA (RT1av1) strains produced moderate amounts of antibody; while the BN (RT1n) strain produced strong primary and secondary antibody responses. This suggested that the BN strain was able to process and present the RT1-Dbu peptide on its class II molecules. In vitro proliferation studies demonstrated that LEW T cells did not respond to the peptide, whereas BN T cells responded strongly, and that the response in the BN strain was found only in the CD4+ T-cell subset. However, immunisation of BN rats with the RT1-Dbu peptide failed to cause any acceleration of rejection of WAG skin or kidney grafts. Moreover, BN rats primed with WAG skin and kidney grafts did not produce T cells reactive to the RT1-Dbu synthetic peptide. This suggests that the T-cell response of the BN strain to the synthetic major histocompatibility complex peptide was not relevant to the indirect T-cell allo-recognition response to naturally processed RT1-Du beta chains.