IDENTIFICATION AND KINETICS OF 2 RECENTLY BONE-MARROW-DERIVED B-CELL POPULATIONS IN PERIPHERAL LYMPHOID-TISSUES

In rats, the glycoprotein Thy-1 is expressed on recently bone marrow ( BM)-generated B cells but not on mature recirculating follicular (RF) B cells. Here we demonstrate that Thy-1(+) B cells consist of two phen otypically distinct, but developmentally related, populations: a popul ation of newly formed (NF) B cells (IgM(br)-IgD(du)) that give rise to the second, less immature, Thy-1(+) population of so-called early rec irculating follicular (ERF) B cells (Thy-1(+)IgM(du)IgD(br)) cells. Th ese cells ultimately develop to RF-B cells (Thy-1(-)IgM(br)IgD(du)). K inetic studies reveal that in absolute numbers per day most cells die at the transition of NF-B cells in the BM and those in the periphery: less cells die at later stages of B cell differentiation. Given the no tion that this cell loss is not random, we speculate that NF-B cells a nd ERF-B cells may represent crucial steps during peripheral B cell de velopment and their selection. Identification of their unique phenotyp e makes it possible to evaluate their roles in development of the anti body repertoire. (C) 1995 Academic Press, Inc.