CD1d expression by dendritic cells and CD40L or ICOS expression by NKT cells is dispensable for NKT-enhanced humoral immunity (61.16)

Abstract CD1d-binding glycolipids have potent adjuvant effects on T-dependent humoral immune responses to co-administered protein antigen. We reported previously that cognate interactions between CD1d expressed on B cells and the T cell antigen receptor of natural Killer T (NKT)was critical for the adjuvant effect of the CD1d ligand α-galactosyl ceramide (α-GC). We have therefore tested the hypothesis that CD1d-expressing dendritic cells contribute to NKT-enhanced antibody production and that NKT cells provide co-receptor-mediated B cell help. Using bone marrow chimera approaches, we demonstrate that CD1d-expression by dendritic cells as well as CD40L and ICOS expression by NKT cells are dispensable for the adjuvant effects of α-GC. This reinforces the concept that the primary mode of NKT activation is through CD1d-expressing B cells and indicates that NKT cells utilize mechanisms distinct from that of helper T cells to provide specific B cell help.