Individual antigen-specific T lymphocytes: helper function in enabling the expression of multiple antibody isotypes

In recent years antigen-specific T cells have been shown to be capable of mediating a number of diverse functions in collaboration with B cells in humoral immune responses. One of the more intriguing roles attributed to helper T cells is the promotion of the synthesis of multiple immunoglobulin isotypes by B cells in T-dependent antibody responses. The experiments presented in this report were carried out to determine if an individual antigen-specific T lymphocyte has the capability to enable the production of antibodies of multiple immunoglobulin heavy chain isotypes. We describe an experimental system which allows for the isolation and antigenic stimulation of individual helper T cells in a splenic environment which provides an excess of primary B cells for collaboration with isolated T lymphocytes. Employing this system we have demonstrated that an individual antigen- specific T lymphocyte, specific for the PR8 strain of influenza virus, has the capacity to enable primary B-cell PR8-specific antibody responses of more than a single immunoglobulin isotype. The implications made by these studies regarding the problem of genetic restrictions regulating T-cell-B-cell interaction is discussed.