LONG-TERM CULTURE SYSTEM FOR SELECTIVE GROWTH OF HUMAN B-CELL PROGENITORS

We describe a simple reproducible system for enrichment and long-term culture of human B-cell progenitors, Enriched CD34(+) cord blood monon uclear cells are seeded onto a murine stromal cell line to establish a biphasic culture system. These cultures are characterized by transien t growth of myeloid cells followed by outgrowth of cells highly enrich ed for early B-cell progenitors, Cultures consisting of >90% early B-l ineage cells [expressing CD10, CD19, CD38, and CD45 but lacking CD20, CD22, CD23, and surface IgM] are maintained for >12 weeks without grow th factor addition. Cells remain predominantly germ line at the immuno globulin locus and express only low levels of cytoplasmic mu chain, te rminal deoxynucleotidyltransferase, and recombination-activating gene 1 product, They are unresponsive to the pre-B-cell growth factors inte rleukin 7 or stem cell factor, or both, suggesting that growth support is provided by a cross-reactive murine stromal cell factor, Cultured B-cell progenitors are generated in large numbers (>10(8) cells from a typical cord blood specimen) suitable for use in biochemical analysis and gene-transfer studies, This system should be useful for study of normal and abnormal early human B-lymphopoiesis.