[Endogenous neddylation in B cells regulates immune responses in mice]

To investigate the regulatory role of endogenous neddylation in B cell-mediated immune responses.

B cell-specific Ube2m knockout mice (CD19^cre/+Ube2m^fl/fl) were generated using the Cre-LoxP system, with littermate Ube2m^fl/flmice serving as normal controls. Mice were immunized with thymus-independent antigens 4-hydroxy-3-nitrophenylacetyl (NP)-lipopoly saccharide (LPS) and 2,4-dinitrophenyl (DNP)-Ficoll, as well as thymus-dependent antigens NP-chicken gamma globulin (CGG) and DNP-keyhole limpet hemocyanin (KLH). Serum levels of specific antibodies were measured by enzyme-linked immunosorbent assay (ELISA). Flow cytometry was used to determine the proportions of splenic germinal center B cells, splenic plasma cells, and bone marrow plasma cells in mice immunized with NP-LPS or NP-CGG. Statistical analyses were performed to assess differences in immune responses among the groups.

Compared with controls, Ube2m-deficient mice showed significantly lower levels of anti-NP immunoglobulin (Ig)G2a, IgG2b, IgG2c, and IgG3 after NP-LPS immunization, and reduced levels of all anti-DNP IgG subclasses after DNP-Ficoll immunization (all P<0.05), with no significant change in IgM levels. The proportions of total splenic germinal center B cells, total bone marrow plasma cells, and NP-specific plasma cells were also significantly decreased after NP-LPS immunization (all P<0.01). Following immunization with NP-CGG or DNP-KLH, Ube2m knockout mice exhibited reduced levels of anti-NP or anti-DNP IgM and all IgG subclasses (all P<0.05), with antigen-dependent differences in the timing and extent of antibody reduction. After NP-CGG immunization, the proportions of total splenic plasma cells, NP-specific plasma cells, and NP-specific germinal center B cells were markedly decreased (all P<0.01).

Endogenous neddylation deficiency in B cells broadly impairs immune responses to both thymus-independent and thymus-dependent antigens in mice, and its regulatory effects are antigen-dependent.