Genetic control of sensitivity to moloney leukemia virus in mice. VI. Involvement of virus-specific T helper cells collaborating with B cells.

T cell responses to Moloney virus involve cytolytic and helper lymphocytes. In contrast to specific cytolytic T lymphocytes, few studies have been devoted to the characteristics of helper T cells for antibody production. The present experiments describe an assay for Moloney virus-specific help for B cells using dinitrophenylated virus. This method, using the Moloney virus as a carrier in a hapten-carrier system, allows to definition of the specific helper function of antibody responses. T helper cells were induced in murine sarcoma virus or inactivated Moloney murine leukemia virus-primed spleens or lymph nodes. T helper function was due to Thy-1.2, Lyt-1+2- cells and was macrophage-dependent. It was stimulated by whole virus of Moloney gp71 envelope protein but not Moloney p30 internal protein. Cross-reactive stimuli were obtained with other dinitrophenylated type C viruses. High and low responses were correlated respectively with resistance and susceptibility to Moloney leukemia virus. Cultures of helper T cells with preserved activity have been established and maintained for one month.