title: Inhibition of CD10/neutral endopeptidase 24.11 promotes B-cell reconstitution and maturation in vivo.
abstract: The common acute lymphoblastic leukemia antigen [(CALLA) CD10, neutral endopeptidase 24.11 (NEP)] is a cell-surface zinc metalloprotease expressed by a subpopulation of early murine B-lymphoid progenitors and by bone marrow stromal cells that support the earliest stages of B lymphopoiesis. In previous in vitro studies in which uncommitted murine hematopoietic progenitors plated on a stromal cell layer differentiate into immature B cells, the inhibition of CD10/NEP increased early lymphoid colony numbers. To further characterize CD10/NEP function during lymphoid ontogeny in vivo, we utilized a Ly5 congenic mouse model in which the lymphoid differentiation of uncommitted hematopoietic progenitors from Ly5.1 donors was followed in sublethally irradiated Ly5.2 recipients treated with a specific long-acting CD10/NEP inhibitor (N-[L-(1-carboxy-2-phenyl)ethyl]-L-phenylalanyl-beta- alanine (SCH32615)). The expression of Ly5.1, B220, and surface IgM (sIgM) was utilized to characterize donor-derived hematopoietic cells (Ly5.1+), B lymphocytes (B220+), and mature B cells (B220+ sIgM+) from the lymphoid organs of recipient animals treated with SCH32615 or vehicle alone. SCH32615-treated animals had higher percentages of Ly5.1+ donor splenocytes than animals treated with vehicle alone (16.9% vs. 10.4%, 63% increase, P = 0.013). Animals treated with the CD10/NEP inhibitor also had relatively more Ly5.1+ splenic B (B220+) cells than vehicle-treated animals (14.4% vs. 8.2%, 75% increase, P = 0.018). To more specifically characterize the effects of CD10/NEP inhibition on B-cell differentiation, Ly5.1+ splenocytes from animals treated with SCH32615 or vehicle alone were analyzed for coexpression of B220 and sIgM. Animals treated with the CD10/NEP inhibitor had a significantly higher percentage of mature donor B cells (Ly5.1+ B220+ sIgM+, 10.2% vs. 5.2%, 90% increase, P = 0.006) and a more modest relative increase in immature donor B cells (Ly5.1+ B220+ sIgM-, 4.7% vs. 3.4%, 38% increase, P = not significant). Taken together, these results suggest that CD10/NEP inhibition promotes the reconstitution and maturation of splenic B cells. Therefore, CD10/NEP may function to regulate B-cell ontogeny in vivo by hydrolyzing a peptide substrate that stimulates B-cell proliferation and/or differentiation.
authors.affiliation: Laboratory of Immunobiology, Dana-Farber Cancer Institute, Boston, MA 02115.
authors.forename: G
authors.initials: G
authors.lastname: Salles
authors.forename: H R
authors.initials: HR
authors.lastname: Rodewald
authors.forename: B S
authors.initials: BS
authors.lastname: Chin
authors.forename: E L
authors.initials: EL
authors.lastname: Reinherz
authors.forename: M A
authors.initials: MA
authors.lastname: Shipp
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000187:drug effects / Q000201:enzymology / Q000276:immunology*; D004151:Dipeptides / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D007075:Immunoglobulin M / Q000378:metabolism; D008198:Lymph Nodes / Q000201:enzymology / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D015260:Neprilysin / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D010641:Phenotype; D013154:Spleen / Q000201:enzymology / Q000276:immunology
chemical_list: D004151:Dipeptides; D007075:Immunoglobulin M; C062344:SCH 32615; D015260:Neprilysin