Figure 4.

Modulation of IgM in response to antigen does not depend on Syk. (A) Two-color flow cytometry of bone marrow cells from syk+/− and syk−/− Ig^HEL chimeric mice in the absence of autoantigen or the presence of sHEL or mHEL. The windows containing immature (1) and mature (2) B cells are indicated. Plots are representative of six chimeras. (B) Overlaid histograms of IgM expression (HEL/Hy9Tc fluorescence) on immature Ig^HEL B cells in the presence or absence of sHEL autoantigen. (C) Mode expression of HEL-binding BCRs on the surface of immature Ig^HEL B cells from syk−/− and syk+/− chimeric mice, developing in the absence of autoantigen or the presence of sHEL or mHEL. Histograms represent arithmetic means and dots individual animals. (D) Median IgM^a receptor levels on naive, immature B220^lo Ig^HEL B cells from the bone marrow of syk−/− (squares) or syk+/− (circles) mice, after incubating in vitro for varying lengths of time with 1 μg/ml HEL (closed points) or with media alone (open points).