Helper function of CD4+ lymphocytes in antiviral immunity in ginbuna crucian carp, Carassius auratus langsdorfii

Although many recent studies have suggested that CDzr helper T cell (Th-cell) functions are well conserved among teleost fishes and mammals, there is little evidence that CDT' Th-cells in fish are actually involved in both humoral and cell-mediated immunity during a secondary immune response. In the present study, adoptive transfer using clonal ginbuna crucian carp and crucian carp hematopoietic necrosis virus (CHNV) was used to investigate the functions of CDT' cells during humoral and cell-mediated immunity. With regard to humoral immunity, transplanting CHNV-sensitized donor cells, containing OA(+) cells, into naive fish induced more rapid and stronger antibody production than by transplanting non-sensitized donor cells or sensitized donor cells lacking CIA(+) cells. During cell-mediated immunity, no significant differences were found in recipients that received sensitized cells regardless of whether the donor cells contained CD4+ cells, although recipients that received both sensitized donor cells (with and without CD4+ cells) exhibited more efficient cell-mediated cytotoxicity than those that received nonsensitized donor cells. These findings suggest that inducing a secondary antibody response requires CD4+ cell help, and secondary cell-mediated immunity can be induced both by CDir cells and leukocytes other than CD4+ cells. (C) 2013 Elsevier Ltd. All rights reserved.