All T15 Id-positive antibodies (but not the majority of VHT15+ antibodies) are produced by peritoneal CD5+ B lymphocytes

Abstract

After adult irradiation and reconstitutlon with autologous bone marrow, BALB/c and C.B20 mice no longer utilize the T15 Id In response to phosphorylchollne. T15 Id expression can be restored by transfers of peritoneal B cells or by FACS-purlfled CD5⁺ IgM⁺ lymphocytes (but not by T lymphocytes) from syngenelc donors. Using bone marrow and peritoneal cell donors that are congeneic for heavy and light chain allotypes, the exclusive origin of the T15 Id In peritoneal B cells was ascertained. These conclusions have been essentially confirmed by Immunization with either antl-T15 Id or antl-V_HT15 antibodies conjugated to llpopolysaccharlde. Thus, the production of V_HT15-positlve antibodies continues at control levels In bone marrow-reconstituted animals while no T15 Id production can be stimulated even In this protocol of direct B cell stimulation. These results constitute the first formal demonstration of the exclusive production of an Id by CD5+ B-cells.