Expression of an X-linked gene family (XLR) in late-stage B cells and its alteration by the xid mutation.

One of the most extensively studied X-linked immunodeficiency disorder is the xid mutation of the mouse strain CBA/N. This mutation may involve a maturational defect as xid animals are unable to raise antibodies to soluble polysaccharide antigens, a function normally attributed to late-stage B cells. Moreover, studies using monoclonal antibodies have defined a B-cell surface antigen (BLA-2 or 14G8) that is expressed on most or all immature B lymphocytes, but not on a subpopulation of mature splenic B lymphocytes; this late-stage, 14G8 antigen-negative splenic B-cell subpopulation is apparently absent from mice bearing the xid defect. In the accompanying paper we describe the isolation of a cDNA clone recognizing a family of genes on the X chromosome, at least some of whose members are closely linked to the xid trait. We report here that this gene family, XLR, is transcribed in certain B- and T-cell lineage tumours, but not in macrophage tumours, or liver or kidney cells. We show that it is transcribed principally in late-stage, 14G8-negative B-cell tumours and plasmacytomas, but not in immature B-cell or pre-B-cell tumours. We are able to detect transcription in all of 12 plasmacytomas (secretory B-cell tumours) derived from mice with normal X chromosomes, but not in three plasmacytomas carrying the xid mutation. These data, combined with the restriction fragment length polymorphism analysis linking the XLR gene family to the xid mutation, suggests that the xid defect occurs within a member of this gene family.