CD1d-Restricted Immunoglobulin G Formation to GPI-Anchored Antigens Mediated by NKT Cells

Abstract
Immunoglobulin G (IgG) responses require major histocompatibility complex (MHC)–restricted recognition of peptide fragments by conventional CD4+helper T cells. Immunoglobulin G responses to glycosylphosphatidylinositol (GPI)- anchored protein antigens, however, were found to be regulated in part through CD1d-restricted recognition of the GPI moiety by thymus-dependent, interleukin-4–producing CD4+, natural killer cell antigen 1.1 [(NK1.1)+] helper T cells. The CD1-NKT cell pathway regulated immunogobulin G responses to the GPI-anchored surface antigens ofPlasmodiumandTrypanosomaand may be a general mechanism for rapid, MHC-unrestricted antibody responses to diverse pathogens.