Spontaneous in vitro occurrence and long-term culture of murine B lymphoblast cell lines.

Under simple culture conditions, in vitro culture of T cell-depleted splenic mononuclear cells reliably promotes the outgrowth of B lymphoblasts. Such cells, termed BLY1, can be propagated as long-term B cell lines but are nontumorigenic in syngeneic recipients. The phenotype of BLy1 cells is unusual. They express certain B cell markers, including surface mu-lambda, I-Ak, and C3 and Fc receptors; however, delta heavy chain and kappa light chain production is absent. Although the cells do not express Thy-1 or Lyt-2, Lyt-1 is readily demonstrable. These distinctive features of BLy1 cells thus resemble a recently described B cell subset prominent early in ontogeny, and in the B cell defect of NZB mice.