Figure 3. Lin^-CD45R^-CD19^- fetal liver derived B-1a cells produce natural IgM antibody that binds pneumococcal antigens.

Serum was obtained from CB17 SCID mice transplanted with Lin^-CD45R^-CD19^- fetal liver cells, Lin^-CD45R^lo/-CD19⁺ fetal liver cells, or total Lin^- bone marrow cells four to five weeks post transfer. The serum was evaluated for (A) total IgM, (B) PC-specific IgM, and (C) PPS3-specific IgM levels by ELISA. As a reference, serum from 3-month old BALB/c-ByJ mice was also evaluated at the same time. The results represent an average of serum samples taken from individual mice, which demonstrated reconstitution by flow cytometry analysis. The number of individual serum samples analyzed per group is as follows: 19 Lin^-CD45R^-CD19^- fetal liver cell chimera mice, 14 Lin^-CD45R^lo/-CD19⁺ fetal liver cell chimera mice, and 6 total Lin^- bone marrow chimera mice.