Induction of HLA class I surface expression recruits low-affinity cytolytic T lymphocytes

Recent studies indicate that the relative expression of HLA class I molecules can play an important role in regulating the cellular immune response. In this report, we used cloned human cytolytic T lymphocytes (CTL) and transfected HLA class I molecules to investigate the effect of HLA class I induction on CTL reactivity. CTL clones with identical antigen specificities but different antigen affinities were compared for their ability to lyse target cells with varying levels of HLA class I expression. The cytolytic reactivity of the high-affinity clone was independent of the level of HLA class I expression. In contrast, cytolytic reactivity of the low-affinity CTL clone was directly related to the level of HLA expression. These data suggest that the induction of HLA class I surface expression has a disproportionate effect on the reactivity of low-affinity CTL and may provide a mechanism for the recruitment of these cells in vivo.