Cytokines elicited by T cell epitopes from a synovial autoantigen: altered peptide ligands can reduce interferon-gamma and interleukin-10 production.

Objective: To explore the cytokine responses associated with T cell epitopes from human cartilage glycoprotein 39 (HC gp-39) and the potential for modifying cytokine secretion using altered peptide ligands (APLs).

Methods: Draining lymph node cells were harvested from HLA-DR*0401 transgenic mice that had been immunized with HC gp-39. Cytokine responses to 5 previously identified HLA-DR*0401-restricted HC gp-39 T cell epitopes were studied in vitro. The anchor and T cell receptor (TCR) contact residues of peptide 322-337 were identified, and this information was used to design alanine-substituted APLs. T cells were primed in vivo with wild-type peptide 322-337, restimulated with wild-type peptide or APLs, and the cytokine profiles were compared.

Results: Restimulation with individual peptides elicited distinct cytokine profiles. HC gp-39 (peptide 322-337) elicited a dominant interferon-gamma (IFNgamma) response. Residues within the core (positions P1-P9) 322-337 peptide sequence were critical for T cell recognition. Surprisingly, the N-terminal flanking region was also important for recognition by 6 of 10 specific T cell hybridomas. Substitutions of charged TCR contact residues in the 322-337 core epitope (E332A and K335A) were associated with a significant reduction in the IFNgamma and interleukin-10 (IL-10) stimulation indices. Restimulation with peptides W325A and V326A was also associated with a trend toward reduced IFNgamma and IL-10 secretion. In contrast, restimulation with peptide D330N elicited cytokine profiles more comparable with those resulting from restimulation with wild-type peptide.

Conclusion: This study indicates that APLs of a proinflammatory HC gp-39 T cell epitope may be used to alter the cytokine response from a memory T cell population.