Affinity maturation of the immune response and the generation of long-lived bone marrow (BM) plasma cells are hallmarks of CD40-dependent, thymus-dependent (TD) humoral immunity. Through disruption of the tumor necrosis factor receptor (TNFR)-associated factor 6 (TRAF6)-binding site within the CD40 cytoplasmic domain, we selectively ablated affinity maturation and the generation of plasma cells after immunization. Mutagenesis of both the TRAF6 and TRAF2-TRAF3 sites was essential for arresting germinal center formation in response to immunization. CD40-induced B cell proliferation and early immunoglobulin production occurred even when all TRAF sites were ablated. These studies show that specific CD40-TRAF associations control well defined aspects of humoral immunity. In addition, they define the roles that TRAF-dependent and TRAF-independent pathways play in regulating antigen-driven B cell differentiation.
Access optionsAccess options
Subscribe to Journal
Get full journal access for 1 year
only $18.75 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Confocal microscopy and flow cytometry was done at the Herbert C. Englert Cell Analysis Laboratory, which was established by equipment grants from the Fannie E. Rippel Foundation, the NIH Shared Instrument Program and Dartmouth Medical School and is supported, in part, by Core Grant CA 23108 from the National Cancer Institute to the Norris Cotton Cancer Center. Supported by NIH grant AI26296 (to R. J. N.) and the American Cancer Society (L. D. E.).
Transgenic CD40 expression in X-CD40 mice. T-depleted splenocytes from Flt3L-treated mice (10 days with 10 µg/mouse/day) were stained with anti-MHC class II (M5) or CD11c and anti–human CD40. Histograms depict anti–human CD40 staining on both class II and CD11c–positive cell populations in each X-CD40 strain. Open histograms depict staining on CD40-/- populations.
Assessment of signaling data in X-CD40 transgenic mice on a murine CD40+ genetic background. Where denoted by the letter M, murine CD40 was engaged with the monoclonal anti-murine CD40 agonistic antibody 1c10. Control experiments were performed at time points of maximal stimulation: 5 min for phospho-IκBα analysis and 10 min for Jnk and p38 MAPK phosphorylation analyses. The expression of endogenous CD40 does not affect the function of the transgenic receptor. (a) Primary cultures of splenic B cells from unimmunized X-CD40 transgenic mice were stimulated in vitro with 1000 ng/ml of shCD154 for the times indicated in minutes. Cells were lysed, and lysates were immunoblotted with antibodies against the phosphorylated TpY motif of Jnk2. Both isoforms of phosphorylated Jnk, p54 and p46, are recognized by the primary antibody. (b) Analysis of p38 MAPK activation in primary splenic B cells treated with shCD154. Cells were stimulated for indicated times, lysed and analyzed by immunoblot with an antibody against the phosphorylated TpY motif of p38 MAPK. (c) Analysis of NF-kB activation in primary splenic B cells. Cells were treated with shCD154 for the times indicated, lysed and analyzed by immunoblot using an antibody against phospho–Ser32-IkBa. For all the signaling experiments, the data presented are representative of 3 or more independent experiments.
Testing doses of shCD154 for induced B cell proliferation. Primary splenic B cells were cultured for 60 h with indicated doses of shCD154 plus IL-4 and IL-5. Cultures were supplemented with 1µCi of [3H]thymidine, and continued for an additional 12 h. After 72 h total culture time, cells were harvested, and genomic DNA was tested for incorporation of [3H]thymidine by scintillation counting. Proliferation was indistinguishable in all mice at doses above 200 ng/ml. In all mice, proliferation was diminished at doses below 100 ng/ml.