RHOF PROMOTES MURINE MARGINAL ZONE B CELL DEVELOPMENT

RhoF is a member of the Rho GTPase family that has been implicated in various cell functions including long filopodia formation, adhesion, and migration of cells. Although RhoF is expressed in lymphoid tissues, the roles of RhoF in B cell development remain largely unclear. On the other hand, other members of the Rho GTPase family, such as Cdc42, RhoA, and Rac, have been intensively studied and are known to be required for B cell development in the bone marrow and spleen. We hypothesized that RhoF is also involved in B cell development. To examine our hypothesis, we analyzed B cell development in RhoF knockout (KO) mice and found a significant reduction in marginal zone (MZ) B cells in the spleen, although T cell development in the thymus and spleen was not affected. Consistent with these results, the width of the MZ B cell region in the spleen was significantly reduced in the RhoF KO mice. However, the antigen-specific antibody titer of IgM and IgG3 after MZ B cell-specific antigen (T cell-independent antigen, type I) stimulation was not affected by RhoF deletion. Furthermore, we demonstrated that RhoF was dispensable for stromal cell-derived factor-1α- and B lymphocyte chemoattractant-induced B cell migration. These results suggest that RhoF promotes MZ B cell development in the spleen.