MATURATION STAGES OF MOUSE DENDRITIC CELLS IN GROWTH FACTOR-DEPENDENTLONG-TERM CULTURES

The signals controlling the checkpoints of dendritic cells (DC) matura tion and the correlation between phenotypical and functional maturatio nal stages were investigated in a defined model system of growth facto r-dependent immature mouse DC. Three sequential stages of DC maturatio n (immature, mature, and apoptotic) were defined and characterized. Im mature DC (stage 1) had low expression of costimulatory molecules, hig hly organized cytoskeleton, focal adhesion plaques, and slow motility; accordingly, they were very efficient in antigen uptake and processin g of soluble proteins. Further, at this stage most of major histocompa tibility complex class II molecules were within cytoplasmic compartmen ts consistent with a poor allostimulatory capacity. Bacteria or cytoki nes were very efficient in inducing progression from stage 1 towards s tage 2 (mature). Morphological changes were observed by confocal analy sis including depolymerization of F-actin and loss of vinculin contain ing adhesive structures which con-elates with acquisition of high moti lity. Antigen uptake and presentation of native protein antigen was re duced. In contrast, presentation of immunogenic peptides and allostimu latory activity became very efficient and secretion of IL-12 p75 was d etectable after antigen presentation. This functional DC maturation en ded by apoptotic cell death, and no reversion to the immature phenotyp e was observed.