Cloning of B cells from autoimmune MRL-lpr/lpr and MRL.xid mice

The relationship between colony formation (cloning) of B cells and their activation in murine autoimmunity was investigated in MRL-lpr/lpr and MRL.xid mice. Cells from MRL-lpr/lpr mice showed similar requirements for in vitro growth as normal CBA/J and BALB/c cells, with maximal colony formation in the presence of the supporting factors lipopolysaccharide and sheep red blood cells. The frequency of colony-forming cells from MRL-lpr/lpr spleens or hapten-specific B-cell preparations was slightly greater than the two normal control strains, with this difference significant only for a comparison of BALB/c and MRL-lpr/lpr spleens. In contrast, MRL-lpr/lpr mice bearing the xid gene for B-cell immunodeficiency (MRL.xid) had markedly reduced B-cell colony formation. These mice nevertheless expressed anti-DNA antibodies, although at levels reduced from that of MRL-lpr/lpr controls. These results indicate that enhanced in vitro colony formation need not accompany B-cell hyperactivity in murine autoimmune disease and that autoantibody production can occur in mice with impairment in this growth property.