Involvement of ERK, p38 MAP kinase, and PKC in MHC class II-mediated signal transduction in a resting B cell line

Substantial evidence suggests that MHC class II molecules play a critical role in transducing signals during B cell activation and differentiation. In addition, we previously found that cross-linking of MHC class II molecules using anti-MHC class II antibodies inhibited NF-κB activation in resting B cells isolated from mouse spleen. In this study, we investigated the mechanism of anti-MHC class II antibody-mediated inhibition of LPS-induced NF-κB activation using a resting B cell line, 38B9. We found that treatment with a corresponding anti-MHC class II antibody reduced the activation of NF-κB in LPS-stimulated 38B9 cells, treatment of the antibody mediated down-regulation of PKC and ERK/p38 MAP kinase pathways, and treatment with PKC inhibitors caused down-regulation of ERK and p38 MAP kinase activities in LPS-stimulated 38B9 cells. Our results suggest that the PKC and ERK/p38 MAP kinase pathways are regulated by anti-MHC class II antibodies, and that MHC class II molecules are actively involved in the signal transduction pathway in the resting B cell line, 38B9. Consequently, disruption of these pathways might contribute to the inhibition of LPS-induced NF-κB activation in 38B9 cells.