Regulatory function of Thy 1 negative cells: II. Spontaneous release of enhancing product by B cells cultured in vitro

Abstract

The supernatant from non-antigen- and non-mitogen-stimulated spleen cells, cultured for 2 days, is effective in augmenting the IgM primary antibody response to TD antigens. The IgM and IgG secondary response to TD antigens, as well as the IgM response to TI antigens is not affected. Neither T cells nor accessory cells seem to be responsible for the release of the enhancing product. The soluble factor described in this paper (i) is not a polyclonal activator of B cells, (ii) does not substitute for thymus-derived cell functions in the in vitro response to heterologous erythrocytes, (iii) does not promote the response to optimal and suboptimal doses of Con A. It modulates the antibody production only in conjunction with T cells and in the presence of macrophages. Studies carried out with mouse myeloma cell lines confirmed present results obtained with normal spleen cells. A soluble product which exhibits the biological activities ascribed to the BEF and which prevents the activation of T suppressor cells was produced by a B-cell clone that does not express immunoglobulin heavy or light chains (P. del Guercio, S. Brugère, and M. F. Poirier, Cell. Immunol., in press).