X-chromosome-linked immune-deficient mice have B-1b cells.

The B lymphocyte subsets of X-chromosome-linked immune-deficient (XID) mice were examined by flow cytometric analyses of spleen and peritoneal cells. As shown in prior studies, young adult XID mice had reduced representation of the CD5+ (B-1a) subset in their peritoneal cavity. However, the CD11b+ (B-1b) B-cell subset was present and exhibited the IgM(hi) CD45(lo) CD23- phenotype characteristic of most B-1 cells. Although present at a lower frequency than that found in their normal counterparts, B-1b cells were evident in CBA/N and (XD2J)F1 male mice. With increasing age, B-1b cell number increased and in the oldest XID mice were present as B-cell chronic lymphocytic leukaemia. These results show that XID mice do have B-1 cells, particularly the B-1b subset.