Peptide binding by empty cell-surface class II MHC molecules.
(A–E) Peptide binding to cell-surface IAs
on bone marrow-derived DC in various developmental states
(A–C), B-cell blasts (D), or macrophages
(E), by using 100 μM fluorescent antigenic peptide
PLP[139–151] (shaded) or control peptide PLP[39–50] (unshaded),
detected by flow cytometry. Proportion of cells staining positive for
surface peptide binding: DC (+GM-CSF) 99%, mature DC (−GM-CSF) 81%,
DC (−GM-CSF, +TNF) 29%, macrophages 23%, B-cell blasts 21%.
(F–H) Concentration dependence of antigenic peptide
binding to splenic DC (filled circles) and B-cell blasts (filled
squares) and of control peptide binding to splenic DC (open circles).
(F) PLP[139–151] binding to DC and B cells from SJL
(IAs) mice with nonbinding control peptide PLP[39–50],
(G) HEL[48–62] binding to B10.Br (IAk)
cells with control peptide OVA[323–336], and (H)
AchR[148–162] binding to C57/Bl6 (IAb) cells with
control peptide MBP[1–11].