TRAF5 Deficiency Ameliorates the Severity of Dextran Sulfate Sodium Colitis by Decreasing TRAF2 Expression in Nonhematopoietic Cells

The Role of TNF Receptor-Associated Factor 5 in the Formation of Germinal Centers by B Cells During the Primary Phase of the Immune Response in Mice

TNF receptor-associated factors (TRAFs) function as intracellular adaptor proteins utilized by members of the TNF receptor superfamily, such as CD40. Among the TRAF family proteins, TRAF5 has been identified as a potential regulator of CD40. However, it remains unclear whether TRAF5 regulates the generation of germinal center (GC) B cells and antigen-specific antibody production in the T-dependent (TD) immune response. TRAF5-deficient (Traf5-/-) and TRAF5-sufficient (Traf5+/+) mice were immunized in the footpad with 2,4,6-trinitrophenol-conjugated keyhole limpet hemocyanin (TNP-KLH) and complete Freund's adjuvant (CFA). We found that GC B cell generation and antigen-specific IgM and IgG1 production were significantly impaired in Traf5-/- mice compared to Traf5+/+ mice. The expression levels of CD40-target genes Fas and Lta, which are involved in GC formation, were significantly decreased in B220+ cells isolated from immunized Traf5-/- mice. Traf5-/- B cells showed decreased antibody production, proliferation, and induction of CD40-target genes Tnfaip3, Tnfsf4, and Cd80 in response to agonistic Fc-CD40L protein in vitro. Furthermore, administration of TNP-KLH and Fc-CD40L to Traf5-/- mice resulted in a severe loss of GC B cell development. These results highlight the crucial role of TRAF5 in driving CD40-mediated TD immune response in vivo.

Functional Analysis of the Transcriptional Regulator IκB-ζ in Intestinal Homeostasis

BACKGROUND

The Toll-like receptor signaling pathway contributes to the regulation of intestinal homeostasis through interactions with commensal bacteria. Although the transcriptional regulator IκB-ζ can be induced by Toll-like receptor signaling, its role in intestinal homeostasis is still unclear.

AIMS

To investigate the role of IκB-ζ in gut homeostasis.

METHODS

DSS-administration induced colitis in control and IκB-ζ-deficient mice. The level of immunoglobulins in feces was detected by ELISA. The immunological population in lamina propria (LP) was analyzed by FACS.

RESULTS

IκB-ζ-deficient mice showed severe inflammatory diseases with DSS administration in the gut. The level of IgM in the feces after DSS administration was less in IκB-ζ-deficient mice compared to control mice. Upon administration of DSS, IκB-ζ-deficient mice showed exaggerated intestinal inflammation (more IFN-g-producing CD4⁺ T cells in LP), and antibiotic treatment canceled this inflammatory phenotype.

CONCLUSION

IκB-ζ plays a crucial role in maintaining homeostasis in the gut.