Function of bone marrow stromal cell lines derived from nude mice

We previously reported that in double deficient nude.xid mice B cells failed to develop and their bone marrow did not produce mature B cells in vitro. However, when progenitors from nude.xid bone marrow were placed on a preestablished normal stromal cell line (AC6) they differentiated into surface IgM+ cells. This raised the possibility of a deficiency of nude and nude.xid stromal cells such that they were incapable of supporting the maturation of X-linked immune deficiency (xid) B cells. Here we ask whether bone marrow stromal cells from nude and nude.xid mice have the ability to support xid B cell lymphopoiesis. A primary stromal cell layer derived from nude mice supported xid B cell differentiation in vitro. We derived panels of stromal cell lines by transfection of primary stromal cell layers with a retrovirus encoding SV40 large T Ag. Several bone marrow stromal cell lines derived from nude and nude.xid mice supported xid B cell differentiation from CD43+/CD45 (B220-) to CD45 (B220+) and from CD45 (B220+)/surface IgM- to surface IgM+. Supporting cell lines expressed both IL-7 and insulin-like growth factor I. The frequencies of bone marrow stromal cells capable of supporting xid B cell differentiation were similar in normal, xid, nude, and nude.xid mice. These results demonstrate that nude and nude.xid mice have bone marrow stromal cells with normal abilities to support B cell maturation.