A NOVEL MACROPHAGE RECEPTOR ENHANCES MHC II-PEPTIDE LOADING AND SURFACE EXPRESSION OF A HAPTEN-PROTEIN CONJUGATE

A receptor possessing specificity for fluorescein was previously ident ified on murine macrophage. The goal of the present study was to deter mine if this receptor influenced MHC II-peptide loading and surface ex pression of a hapten-protein conjugate within murine macrophage. Altho ugh inhibition of fluid-phase pinocytosis had no detectable effect, lo wer levels of intracellular MHC II-peptide complexes were observed upo n inhibition of receptor-mediated endocytosis. Moreover, lower levels of surface expressed MHC II-fluoresceinated peptide complexes were als o detected. Following subcellular fractionation experiments, it was re vealed that the receptor altered the endocytic trafficking of the anti gen within the cell. Namely, degraded antigen and MHC II-peptide compl exes were not observed in dense transferrin receptor positive, catheps in D positive, LAMP-1 positive organelles upon inhibition of the recep tor. Previous studies also suggested that this receptor enhanced MHC I I-peptide loading by concentrating high levels of antigen to endocytic organelles. The implications of these findings on subsequent developm ent of the immune response were also discussed. ((C) Elsevier, Paris).