Absence of Epstein-Barr virus-specific, HLA class II-restricted CD4 super(+) cytotoxic T lymphocytes in infectious mononucleosis

Cytotoxic T lymphocytes (CTL) with the CD4 super(+) phenotype that recognize major histocompatibility complex (MHC) class II antigens are detectable very frequently in cultures of human alloreactive or virus-specific T cells. The significance of these CD4 super(+) CTL for an immune reaction in vivo is not clear. Since Epstein-Barr virus (EBV) transformed B cells express HLA-class I and class II antigens equally well both CD8 super(+) and CD4 super(+) CTL should be stimulated during an acute EBV infection. We analysed the MHC specificity and the phenotype of EBV-specific CTL from patients with infectious mononucleosis (IM). Taken together our results show that cytotoxicity mediated by CD4 super(+) T cells does not play a role in an anti-viral immune response.