Abstract
B-1 cells represent a sub-fraction of B lymphocytes that participate in T cell-independent antibody production and contribute to innate immunity. While the production of B-1 cells is favored during the fetal waves of lymphopoiesis, it has been unclear when and how that differentiation option is specified. To clarify this, lymphoid and hematopoietic progenitors of fetal liver (FL) and adult bone marrow (ABM) were examined for the B cell differentiation potential. Mouse common lymphoid progenitors (CLPs) and more primitive KSL fraction of FL and ABM were transferred to SCID mice and donor-derived B cell subsets were analyzed 4 weeks later. CLPs were also cultured on ST2 stromal cells for 6 days prior to transplantation. While Lin- IL-7Rα+ CLPs from ABM differentiated to B-1, B-2 and marginal zone B (MZB) cells, equivalent cells from d15 FL differentiated mostly to B-1a cells. We found that fetal CLPs had less ability to colonize the bone marrow than adult CLPs. However, the fetal/adult difference was already present when progenitors were cultured in an identical condition before transplantation. More primitive KSL fraction of FL could generate the same broad spectrum of B cells typical of adults, including splenic MZB cells. In conclusion, we argue that FL and ABM-CLPs are intrinsically different regarding B-1/B-2 fates and the difference is acquired just before or coincident with the acquisition of IL-7Rα expression.
Highlights
The humoral immune system is composed of functionally restricted lymphocyte subsets and some of them appear to make natural antibodies without deliberate immunization
Recent reports indicated that proB cells in the adult and fetal bone marrow could be subdivided into B-1 and B-2 progenitors according to their expression of CD19 and CD45R/B220 [17]
Since proB cells, including B-1 progenitors, are derived from common lymphoid progenitors (CLPs) [18,37], B cell fates of CLPs prepared from fetal liver (FL) and adult bone marrow (ABM) were directly compared by transplantation
Summary
BALB/cA and C.B-17/Icr-scid/scid (SCID) mice were purchased from CLEA Japan, Inc (Tokyo, Japan). Cells were counted, stained with FITC-anti-IgM, PE-CD23, PE-Cy7-CD5, APC-CD19, APC-eFluor780-CD45R and Pacific Blue-CD21 Abs and subjected to FACS analysis. Cμ was stained with FITC-conjugated F (ab’) fragment of goat anti-mouse IgM antibody (Southern Biotech). Samples were incubated and PtCbound IgM was detected with goat anti-IgM biotinylated antibody (Southern Biotech) in combination with streptavidin-HRP (BD Bioscience). For measurement of serum IgM, plates were coated with rat anti-mouse IgM mAb (BD Bioscience) and PBS containing 0.05% tween 20 was used as wash buffer. Non-adherent cultured cells were collected, counted and transferred to irradiated SCID mice or stained with FITC-anti-IgM, PE-Cy7-B220, APC-CD19 antibodies and Pacific Blue anti-I-A/I-E antibody that recognizes class II major histocompatibility complex (MHC II), for FACS analysis. Shapiro-Wilk test was performed and the p values between fetal and adult marrow were more than 0.1
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
