Organization and expression of v_h gene families preferentially expressed by ly‐1⁺ (cd5) b cells

Previously we have shown that a high proportion (5%‐15%) of peritoneal Ly‐1⁺ B cells that bind the common membrane phospholipid, phosphatidylcholine, express either of two V_H genes. One of these genes, CH34V_H, belongs to the recently described V_H11 family, whereas the other V_H gene, CH27V_H, is reported here to belong to a new, single‐member family which we designate V_H12. We have characterized these new V_H families in terms of strain polymorphism, map position relative to nine other V_H gene families, and frequency of expression in polyclonally stimulated splenic B cell populations. We find that V_H11 and V_H12 genes are expressed at frequencies similar to the V_H genes of other families in the spleen, and that these genes are not located among the J‐proximal V_H segments which are preferentially expressed during early development. These results suggest that the V_H11 and V_H12 genes are not preferentially rearranged, and support our earlier studies which suggested that the high frequency of V_H11 and V_H12 expression among peritoneal Ly‐1 B cells is due to antigen selection.