T-CELL RECOGNITION OF AN ALLOGENEIC RT1-DB(U) CLASS-II MHC PEPTIDE

The allo-antibody response of several rat strains to an unconjugated s ynthetic 20 amino acid peptide derived from the alpha helical region o f the RT1-D-u beta chain was tested. The LEW (RT1(1)) and WAG (RT1(u)) strains produced little or no antibody; the PVG (RT1(c)) and DA (RT1( av1)) strains produced moderate amounts of antibody; while the BN (RT1 (u)) strain produced strong primary and secondary antibody responses. This suggested that the BN strain was able to process and present the RT1-Db(u) peptide on its class II molecules. In vitro proliferation st udies demonstrated that LEW T cells did not respond to the peptide, wh ereas BN T cells responded strongly, and that the response in the BN s train was found only in the CD4(+) T-cell subset. However, immunisatio n of BN rats with the RT1-Db(u) peptide failed to cause any accelerati on 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 t he RT1-Db(u) synthetic peptide. This suggests that the T-cell response of the BN strain to the synthetic major histocompatibility complex pe ptide was not relevant to the indirect T-cell allo-recognition respons e of naturally processed RT1-D-u beta chains.