MFG-E8 deficiency promotes plasma B cell differentiation of anti-ssRNA specific H564 B cells.

Plasma cell differentiation of id+ B cells was examined in the spleens of 3 month old w.t. and MFG-E8-/- H564 BCR transgenic mice. A: The numbers of id+/B220low plasma cells per 10,000 id+ cells in the spleens were enumerated by flow cytometry. Surface expression of CD138 on id+/B220low cells was significantly higher than id+/B220+ cells. (Histogram: blue—id+/B220+high, red—id+/B220low). B: To locate id+ plasma cells in the spleens, frozen spleen sections from w.t. and MFG-E8-/- H564 mice were stained with anti-CD169(green), anti-B220(blue), and idiotype specific antibody (red). Right: The number of id+ plasma cells in each spleen section was enumerated using Image J. Each data point represents the average of three sections from an individual animal. C: The numbers of id specific IgG producing H564 B cells in the spleens of w.t. and MFG-E8-/-BCR transgenic mice were determined by ELISPOT. D: The titers of id specific IgG, IgG2a, and IgG2b antibodies in the sera of 4 month old w.t. and MFG-E8-/-H564 mice were determined by ELISA. In A-D, each data point represents an individual animal.