A V(H)11V(kappa)9B cell antigen receptor drives generation of CD5(+) B cells both in vivo and in vitro

B lymphocytes can be divided into different subpopulations, some with disti nctive activation requirements and probably mediating specialized functions , based on surface phenotype and/or anatomical location, but the origins of most of these populations remain poorly understood. B cells constrained by transgenesis to produce an Ag receptor derived from a conventional (B-2) t ype cell. develop a B-2 phenotype, whereas cells from mice carrying a B-1-d erived receptor acquire the B-1 phenotype. In this study transgenic enforce d expression of a B cell receptor (mu/kappa) originally isolated from a CD5 (+) (B-1a) B cell generates B-1 phenotype cells in bone marrow cultures tha t show a distinctive B-l function, survival in culture. Despite their autor eactivity, we find no evidence for receptor editing or that the paucity of B-2 cells is the result of tolerance-induced selection. Finally, Ca2+ mobil ization studies reveal a difference between transgenic B-1 cells in spleen and peritoneal cavity, with cells in spleen much more responsive to anti-B cell receptor cross-linking. We discuss these results in terms of specifici ty vs lineage models for generation of distinctive B cell subpopulations.