A human helper‐dependent influenza virus‐specific cytotoxic Tlymphocyte clone restricted by HLA‐DR2

A human influenza A virus-specific cytotoxic T lymphocyte (CTL) clone is described that is restricted by a class II HLA-antigen. Of a large panel of B-lymphoblastoid cell lines (B-LCL) as target cells the clone lysed only infected cells sharing HLA-DR2 with the donor of the clone. In cold target inhibition studies only infected cells bearing HLA-DR2 could inhibit cytotoxicity. Infected PHA-blasts that express less DR-antigen than B-LCL cells were lysed to a much lesser extent though they could be infected equally well. Trypan blue staining and postlabelling of the target cells showed that the clone indeed killed the target cells. The clone did not proliferate in response to infected irradiated autologous LCL cells and had the OKT3+4+8-DR+ phenotype. The possible significance of class II restricted CTL is discussed.