The virus-specific and allospecific cytotoxic T-lymphocyte response to lymphocytic choriomeningitis virus is modified in a subpopulation of CD8⁺ T cells coexpressing the inhibitory major histocompatibility complex class I receptor Ly49G2

The role of negatively signaling NK cell receptors of the Ly49 family on the specificity of the acute CD8⁺ cytotoxic T-lymphocyte (CTL) response was investigated in lymphocytic choriomeningitis virus (LCMV)-infected C57BL/6 mice. Activated CD8⁺ T cells coexpressing Ly49G2 expanded during LCMV infection, and T-cell receptor analyses by flow cytometry and CDR3 spectratyping revealed a unique polyclonal T-cell population in the Ly49G2⁺ fraction. These cells lysed syngeneic targets infected with LCMV or coated with two of three LCMV immunodominant peptides examined. Transfection of these sensitive targets with H2D(d), a ligand for Ly49G2, inhibited lysis. This was reversed by antibody to Ly49G2, indicating effective negative signaling. LCMV characteristically induces an anti-H2(d) allospecific T-cell response that includes T-cell clones cross-reactive between allogeneic and LCMV-infected syngeneic targets. The CD8⁺ Ly49G2⁺ population mediated no allospecific killing, nor was any NK-like killing observed against YAC-1 cells. This study shows that CD8⁺ Ly49G2⁺ cells participate in the virus- induced CTL response but lyse a more restricted range of targets than the rest of the virus-induced CTL population.