Biochemical properties of MHC class II molecules endogenously synthesized and expressed by mouse Langerhans cells

Abstract

The cell surface expression and biosynthesis of Langerhans cells (LC)-derived major histocompatibility complex (MHC) class II molecules from epidermal cells (EC) prepared freshly and cultured for up to 3 days was investigated. Based on the constitutive expression of MHC class II determinants by LC, a panning and magnetic bead selection procedure was employed, yielding 65% and 86% of I-A+ cells, respectively. Phenotypical and cytochemical examinations revealed that the two LC preparations were free of contaminating macrophages as well as B and T cells. Freshly prepared enriched LC were highly efficient in the stimulation of protein antigen-specific T cell clones, while LC purified from short-term cultured EC suspensions proved to be more efficient allogeneic stimulator cells than fresh LC. Comparative analysis of LC obtained from freshly prepared and from short-term-cultured EC preparations indicated an up-regulation of MHC class II determinants during short-term culture. Radioiodination analysis of LC selected by magnetic beads demonstrated prominent class II alpha and beta chain signals with only a minute fraction of invariant chains p35 and p45 being expressed at the cell surface. Unlike class II complexes derived from B cells, those from LC contained invariant chain fragment p20 in association with alpha/beta heterodimers at the plasma membrane. No qualitative differences between freshly isolated and 3-day cultured LC in cell surface expressed MHC class II components were detectable. Metabolic labeling with subsequent two-dimensional electrophoresis revealed distinct features of LC-derived MHC class II molecules with a high proportion of invariant chains in particular gamma and p40 and their extensive sialylation. While fresh and 1-day cultured LC exhibited appreciable levels of newly synthesized class II molecules, a dramatic down-regulation in class II and invariant chain synthesis was measured after 3 days of continuous in vitro culture.

Dendritic cells in Leishmania major‐immune mice harbor persistent parasites and mediate an antigen‐specific T cell immune response

“…This is effected by down-regulating the de novo synthesis of MHC class I1 molecules during differentiation from epidermal Langerhans cells, while migrating from the skin to the draining LN. As a result, the MHC class 11-peptide complexes of dendritic cells have a very long half-life, whereas those of MQ turn over and decrease quickly [40,42,431. In this way, dendritic cells may be very efficient in the continued presentation of Ag from dormant intracellular pathogens, or from degraded organisms, and may be responsible for the maintenance of T cell memory.…”

Diminished Contact Hypersensitivity Response in IL‐4 Deficient Mice at a Late Phase of the Elicitation Reaction

“…Epidermal cell (EC) suspensions were prepared according to Becker et al [17] with modifications using whole pelts. Briefly, the pelts were cut into strips, and treated with 70% isopropanol for 5 s. After rinsing with cold phosphate buffered saline (PBS) strips were incubated in PBS supplemented with 0.5% (w/v) dispase type II (Boehringer-Mannheim, Mannheim, Germany) at 4ЊC overnight.…”

The immunologic properties of epidermal Langerhans cells as a part of the dendritic cell system

“…For an effective generation of a ligand for the antigen-specific T cell receptor (i. e., immunogenic MHC class II/peptide complex) by the antigen-presenting cell, it is necessary that MHC class II molecules and associated invariant chain molecules be available. Biochemical analysis of MHC class II molecules and associated invariant chains in LC showed that freshly isolated LC synthesize large amounts of these molecules [3,27,43]. In parallel with the decline in processing function the synthesis of both molecules was shut down.…”