A phenotypically distinct subset of immature B cells exhibits partial activation, increased survival, and preferential expression of VhS107.
We have observed that immature B cells (IgM(low)IgD(-)) in the bone marrow of adult BALB/c mice exhibit heterogeneity, with a distinct subpopulation ( approximately 4-10%) expressing the CD43/S7 surface protein. These CD43/S7(+) immature B cells often express other surface antigens associated with B cell activation (CD5, CD11b, PD-1). Generation of optimal numbers of CD43/S7(+) immature B cells requires expression of a functional Btk protein, consistent with activation as a requisite for the CD43/S7(+) immature B cell phenotype. Like typical CD43/S7(-) immature B cells, the CD43/S7(+) immature B cells are predominantly resting cells, which are derived from cycling bone marrow B cell precursors. The CD43/S7(+) immature B cell population exhibits enhanced survival in vivo upon administration of the apoptosis-inducing corticosteroid, dexamethasone. Finally, CD43/S7(+) immature B cells show a fourfold increase in incidence of VhS107 micro heavy chain expression compared to the CD43/S7(-) immature B cells. Therefore, in adult murine bone marrow, the presence of a phenotypically distinct immature B cell population can be demonstrated which has undergone partial activation leading to increased survival and BCR-dependent Vh repertoire selection.
Wilson
Emily L
EL
Department of Microbiology and Immunology, University of Miami School of Medicine, Miami 33101, USA.
Sherwood
Erin M
EM
King
Anne M
AM
Riley
Richard L
RL
D000818:Animals; D015703:Antigens, CD; D001402:B-Lymphocytes / Q000502:physiology*; D001854:Bone Marrow Cells / Q000502:physiology*; D002470:Cell Survival; D006412:Hematopoietic Stem Cells / Q000502:physiology; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007075:Immunoglobulin M / Q000032:analysis; D007135:Immunoglobulin Variable Region / Q000235:genetics*; D051917:Leukosialin; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D008808:Mice, Inbred CBA; D010641:Phenotype; D020033:Protein Isoforms; D012795:Sialoglycoproteins / Q000032:analysis; D013154:Spleen / Q000166:cytology
D015703:Antigens, CD; D007143:Immunoglobulin Heavy Chains; D007075:Immunoglobulin M; D007135:Immunoglobulin Variable Region; D051917:Leukosialin; D020033:Protein Isoforms; D012795:Sialoglycoproteins; C497863:Spn protein, mouse