RECONSTITUTION OF B-CELL SUBSETS IN RAG DEFICIENT MICE BY TRANSPLANTATION OF IN-VITRO DIFFERENTIATED EMBRYONIC STEM-CELLS

In vitro differentiated embryonic stem (ES) cells contain a population which is similar to fetal liver pro/pre-B cells on the basis of cell surface antigens and cytoplasmic expression of immunoglobin heavy chai n. This population was purified and transplanted into Rag-1 deficient recipients to characterize its developmental potential in vivo. Follow ing intravenous transfer, these cells rapidly reconstituted the spleni c B bur not the T cell compartment. Reconstitution was transient, indi cating the lack of long-term reconstituting capacity. Similar to fetal liver, B-1 type as well as conventional B cells were generated, accom panied by high serum IgM levels. Intraperitoneal injection generated h igh numbers of peritoneal B cells, predominately of the H-la phenotype , with poor splenic repopulation and low serum IgM levels. These obser vations suggest the emergence of two different B lineage precursor pop ulations during in vitro ES cell differentiation and define a possible role of the microenvironment in directing lymphoid development. (C) 1 997 Elsevier Science B.V.