An established MRL/Mp-lpr/lpr cell line with null cell properties produces a B cell differentiation factor(s) that promotes anti-single-stranded DNA antibody production in MRL spleen cell culture.

The cell line established from the lymph node cells of an MRL/lpr mouse, was found to have null cell properties in that it lacked Thy-1, Lyt-1 and Lyt-2 as well as sIg, and continued to grow in the absence of exogeneously added lymphokines such as IL-2 and IL-3. Interestingly, this cell line (KML1) or a soluble factor(s) produced by it promoted anti-ssDNA antibody production in cultures of MRL/lpr spleen cells. The factor did not induce cell proliferation. Therefore, it is concluded that the cell line KML1 produced at least a B-cell differentiation factor, but not IL-2 or IL-3 as far as detected with the respective lymphokine-dependent cell lines.