BAFF- and APRIL-dependent maintenance of Ab titers after immunization with T-dependent Ag and CD1d-binding ligand

摘要

CD1d-restricted invariant Natural Killer T (iNKT) cells boost humoral immunity to T-dependent Ags that are co-administered with the CD1d-binding glycolipid Ag α-galactosylceramide (α-GC). Observations that mice lacking iNKT cells have decaying Ab responses following vaccination has led to the hypothesis that iNKT cells express plasma cell (PC) survival factors that sustain specific Ab titers. Bone marrow (BM) chimeric mice in which the entire hematopoetic compartment or iNKT cells selectively lacked BAFF, APRIL, or both BAFF and APRIL were created and immunized with NP-KLH adsorbed to Alum or mixed with α-GC. In comparison to BAFF- or APRIL-sufficient BM chimeras, absence of hematopoetic compartment- and iNKT-derived BAFF and APRIL was associated with rapidly decaying Ab titers and reduced PC numbers. The iNKT cell-derived BAFF or APRIL assumed a greater role in PC survival when α-GC was used as the adjuvant for immunization. These results show that iNKT-derived BAFF and APRIL each contribute to survival of PCs induced by immunization. This study sheds new light on the mechanisms through which iNKT cells impact humoral immunity and may inform design of vaccines that incorporate glycolipid adjuvants.