['Antigen-specific CD4 T cells are activated by small numbers of antigenic peptide-MHC class II (pMHC-II) complexes on dendritic cells (DCs).', 'Newly generated pMHC-II complexes are present in small clusters on the DC surface.'] Do major histocompatibility complex ( MHC ) class II-peptide complexes arrive at the plasma membrane in cholesterol-rich microclusters?