betadex and hen-egg-lysozyme-peptide-(46-61)

We investigated differentiation of CD4 T cells responding to Ag presented by bone marrow-derived dendritic cells (DC) in association with MHC class II (MHC II) molecules. Peptides encapsulated in liposomes opsonized by IgG were taken up by endocytosis. MHC II-peptide-specific T cells responding to this Ag were polarized to a Th1 cytokine profile in a CD40-, CD28-, MyD88-, and IL-12-dependent manner. Th2 responses were obtained from the same transgenic T cell population exposed to the same DC on which MHC-peptide complexes had dispersed for 48 h following uptake of FcR-targeted liposomes. DC that took up the same FcR-targeted liposomes and then were exposed to methyl-beta-cyclodextrin, which chelates cholesterol and dissociates lipid microdomains, also stimulated Th2 differentiation. Incubation of T cells with DC incubated with peptides directly binding to MHC II resulted in Th2 responses, whether or not the DC were coincubated with opsonized liposomes as a maturation stimulus. CD4 Th1 polarization thus appears to depend on MHC II-peptide complex clustering in DC lipid microdomains and the time between peptide loading and T cell encounter.

Topics: Animals; Antigen Presentation; beta-Cyclodextrins; CD4-Positive T-Lymphocytes; Centrifugation, Density Gradient; Cyclodextrins; Cytokines; Dendritic Cells; Histocompatibility Antigens Class II; Immunophenotyping; Interleukin-12; Liposomes; Lymphocyte Activation; Membrane Microdomains; Mice; Mice, Inbred CBA; Mice, Transgenic; Muramidase; Peptide Fragments; Receptors, Fc; Th1 Cells; Th2 Cells; Time Factors