Differential expression of CD180 and IgM by B-cell chronic lymphocytic leukaemia cells using mutated and unmutated immunoglobulin VH genes

We have studied the surface expression of the Toll-like receptor family member CD180 on cells from 78 patients with B-chronic lymphocytic leukaemia (B-CLL). B-CLL cells had variable levels of CD180 expression, but this was always less than that expressed by normal blood B cells and was stable for 24 months. Significantly higher levels of CD180 were expressed by B-CLL cells with mutated IGVH genes compared with those using unmutated IGVH genes. This was in contrast to the higher levels of expression of surface immunoglobulin M by B-CLL cells using unmutated, rather than mutated IGVH genes. CD180 was functional on B-CLL cells from some of the patients, as shown by the increased expression of CD86 following incubation in vitro with anti-CD180. The differential expression of CD180 amongst B-CLL patients is one more marker that may define more precisely the different biological properties of this heterogeneous disease.