Defective B cell ontogeny and immune response in human complement receptor 2 (CR2, CD21) transgenic mice is partially recovered in the absence of C3

Mol Immunol. 2007 Jul;44(13):3434-44. doi: 10.1016/j.molimm.2007.02.011. Epub 2007 Mar 26.


Mice prematurely expressing human CR2 (hCR2) in the B cell lineage have a defective B cell ontogeny and immune response. Our recent analysis of this phenotype suggested that signaling through hCR2 and presumably mouse CD19 on the B cell surface, during bone marrow development, could result in the observed changes in B cell function in these mice. To test this hypothesis, we back crossed hCR2(high) transgenic mice onto the CD19(-/-) background. CD19(-/-)hCR2(high) mice were found to possess even fewer mature B cells than their CD19(+/+)hCR2(high) littermates, demonstrating that loss of CD19 exacerbated the effects elicited through hCR2. This data suggests that CD19 provides a survival signal during B cell development in this model. Next, we examined if the removal of the main ligand for CR2, namely C3d, through back-crossing onto the C3(-/-) background could restore normal B cell development. However, we found only minor recovery in peripheral B cell numbers and no obvious change in function. This was despite a three-fold increase in the level of hCR2 expression on B cells isolated from the spleen or bone marrow of C3(-/-)hCR2(high) mice when compared with C3 sufficient littermates. These data demonstrate that hCR2 is integrated in mouse B cell signaling and that the downstream effects of hCR2 expression during early B cell development are partially but not completely due to interaction with C3 fragments and signaling through CD19 in the bone marrow environment.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • B-Lymphocytes / immunology*
  • B-Lymphocytes / metabolism
  • B-Lymphocytes / pathology*
  • Cell Differentiation / genetics*
  • Cell Differentiation / immunology*
  • Complement C3 / deficiency*
  • Complement C3 / genetics
  • Lymphopenia / genetics
  • Lymphopenia / immunology
  • Mice
  • Mice, Knockout
  • Mice, Transgenic
  • Receptors, Complement 3d / genetics*
  • Sheep


  • Complement C3
  • Receptors, Complement 3d