Phenotypic and functional analysis of EBV-specific memory CD8 cells in SLE.

T cell dysfunction has been described in systemic lupus erythematosus (SLE). However, the specific phenotype and function of antigen-specific CD8 cells is less clear. Here we determined phenotype and function of Epstein-Barr virus (EBV)-specific CD8 cells at the single-cell level in SLE. HLA-A2-restricted EBV-BMLF-1-specific CD8 cells were enumerated by flow cytometry using tetramers in SLE and healthy control subjects. Antigen-specific CD8 cells were analyzed for expression of differentiation, activation, proliferation, and anti-apoptotic markers. EBV-specific, other virus-specific (specific against a viral peptide pool consisting of cytomegalovirus, EBV and influenza virus peptides), and mitogen-induced CD8 cell function was assessed by INF-gamma ELISPOT assay. Frequencies of EBV-specific CD8 cells tended to be greater in SLE subjects than in healthy control subjects (p=0.07). While over 10% of EBV-specific CD8 cells were capable of producing IFN-gamma in four out of five healthy control subjects, such proportions of EBV-specific CD8 cells capable of IFN-gamma production were observed in only one out of six SLE subjects (p=0.04). In contrast, viral peptide pool-specific and mitogen-induced IFN-gamma-producing T cell function was intact in SLE subjects. Phenotypic analysis revealed EBV-specific CD8 cells to be in an early to intermediate differentiation and resting memory state in both groups. While EBV-specific CD8 cells are similar in phenotype, their frequency tends to be increased, and function appears to be decreased in SLE. Therefore, an impaired EBV-specific CD8 immune response may exist in SLE, potentially contributing to disease pathogenesis.