Class II-targeted antigen is superior to CD40-targeted antigen at stimulating humoral responses in vivo.

We examined the efficacy of using monoclonal antibodies to target antigen (avidin) to different surface molecules expressed on antigen presenting cells (APC). In particular, we targeted CD40 to test whether the "adjuvant" properties of CD40 signaling combined with targeted antigen would result in enhanced serologic responses. We targeted avidin to class II as a positive control and to CD11c as a negative control. These surface proteins represent an ensemble of surface molecules that signal upon ligation and that are expressed on professional APC, in particular dendritic cells (DC). We observed that targeting class II molecules on APC was superior to targeting CD40, or CD11c. However, CD40 and CD11c could function as targets for antigen bound monoclonal antibodies under certain conditions. Interestingly, inclusion of anti-CD40 mAb with the targeting anti-class II-targeted antigens negatively affects humoral response, suggesting that CD40 signaling under certain conditions may suppress processing and/or presentation of targeted antigen.

Integration of the NF-kappaB and mitogen-activated protein kinase/AP-1 pathways at the collagenase-1 promoter: divergence of IL-1 and TNF-dependent signal transduction in rabbit primary synovial fibroblasts.

Collagenase-1 (MMP-1) is a protease that is expressed by stromal cells and that is involved in remodeling of the extracellular matrix. IL-1 and TNF-alpha enhance collagenase secretion by stromal cells, and chronic exposure of cells to these cytokines can contribute to connective tissue disease. In this study, we show that the NF-kappaB pathway is required for activation of collagenase-1 transcription in rabbit primary synovial fibroblasts (RSF). Although both IL-1 and TNF activate NF-kappaB in these cells, only IL-1 induces collagenase-1 transcription. We have reported previously that NF-kappaB and AP-1 cooperate to mediate IL-1-induced MMP-1 transcription. Here, we show that IL-1 is superior to TNF at inducing c-Jun synthesis, phosphorylation and binding activity in RSF. Similarly, IL-1 is more effective at activating the mitogen-activated protein kinases (MAPK), including the extracellular signal-regulated kinases (ERK), which are required for IL-1-induced MMP-1 transcription. Thus stimulation of the ERK and AP-1 pathways is an essential component of MMP-1 transcriptional activation, which is deficient in TNF-treated cells. These studies demonstrate cooperation between the MAPK and NF-kappaB signaling pathways for IL-1-dependent collagenase-1 transcription, and they define a dichotomy of IL-1- and TNF-elicited signaling that is relevant to cytokine-mediated connective tissue disease.