Essential Roles of Perforin in Antigen-Specific Cytotoxicity Mediated by Human CD4~+ T Lymphocytes: Analysis Using the Combination of Hereditary Perforin-Deficient Effector Cells and Fas-Deficient Target Cells~1

摘要

Although the cytotoxic mechanisms of murine CTLs have been investigated extensively using various mutant and knockout mice, those of human CTLs, especially CD4~+ CTLs, are still obscure. To clarify the roles of perforin in Ag-specific cytotoxicity mediated by human CD4~+ CTLs, alloantigen-specific and HSV-specific human CD4~+ T lymphocyte bulk lines and clones were established from a patient with hereditary perforin deficiency and her healthy facther, and their cytotoxic activities were investigated. Al-loantigen-specific CD4~+ T lymphocytes expressing perforin exerted cytotoxicity against Fas-negative as well as Fas-positive al-logeneic B lymphoblastoid cell lines established from members of a family iwth hereditary Fas deficiency. Perforin-deficient, but not perforin-exprssing, CD4~+ T lymphocytes could exert relatively low level cytotoxicity against allogeneic IFN-gamma-treated keratinocytes. Although cytotoxicity mediated by perforin-expressing CD4~+ CTLs was almost completely inhibited by concana-mycin A, a potent inhibitor of the perforin-mediated cytotoxic pathway, cytotoxicity against IFN-gamma-treated keratinocytes mediated by perforin-deficient CD4~+ T lymphocytes was inhibited only partially by concanamycin A, but was inhibited significantly by antagonistic anti-Fas Ab and anti-Fas ligand Ab. The combination of perforin-deficient effector T lymphocytes and Fas-negative target cells used in the present study provides a novel experimental system for studying the detailed mechanisms of human CTL-mediated cytotoxicity. The present data demonstrate that perforin-negative CD4~+ CTLs can exert cytoxicity against Fas-sensitive target cells; however, perforin plays essential roles in Ag-specific cytotoxicity mediated by human CD4~+ as well as CD8~+ CTLs.