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Maturation stages of mouse dendritic cells in growth factor-dependent long-term cultures
C Winzler1, P Rovere, M Rescigno
1CNR Centre of Cellular and Molecular Pharmacology, Milan, Italy.
Insights
Dendritic cells (DCs) undergo distinct maturation stages, transitioning from efficient antigen uptake in immature states to enhanced immune signaling in mature states, ultimately leading to apoptosis. This study defines these DC maturation checkpoints and their functional consequences.
Area of Science:
- Immunology
- Cell Biology
Background:
- Dendritic cells (DCs) are crucial antigen-presenting cells that bridge innate and adaptive immunity.
- Understanding DC maturation is key to controlling immune responses.
Purpose of the Study:
- To investigate the signals controlling dendritic cell (DC) maturation.
- To correlate phenotypical and functional stages of DC maturation.
Main Methods:
- Defined model system of growth factor-dependent immature mouse DCs.
- Characterization of three sequential DC maturation stages (immature, mature, apoptotic).
- Confocal analysis to observe morphological changes.
Main Results:
- Immature DCs exhibit high antigen uptake and processing but low allostimulatory capacity.
- Maturation, induced by bacteria or cytokines, involves cytoskeletal changes, increased motility, reduced antigen uptake, and enhanced peptide presentation and allostimulatory activity.
- Mature DCs secrete IL-12 p75 after antigen presentation.
- DC maturation progresses sequentially and irreversibly towards apoptosis.
Conclusions:
- DC maturation is a stepwise process with distinct phenotypical and functional characteristics.
- Maturation shifts DCs from antigen-capturing cells to potent immune activators.
- The process is unidirectional, culminating in apoptotic cell death.
Abstract:
The signals controlling the checkpoints of dendritic cells (DC) maturation and the correlation between phenotypical and functional maturational stages were investigated in a defined model system of growth factor-dependent immature mouse DC. Three sequential stages of DC maturation (immature, mature, and apoptotic) were defined and characterized. Immature DC (stage 1) had low expression of costimulatory molecules, highly organized cytoskeleton, focal adhesion plaques, and slow motility; accordingly, they were very efficient in antigen uptake and processing of soluble proteins. Further, at this stage most of major histocompatibility complex class II molecules were within cytoplasmic compartments consistent with a poor allostimulatory capacity. Bacteria or cytokines were very efficient in inducing progression from stage 1 towards stage 2 (mature). Morphological changes were observed by confocal analysis including depolymerization of F-actin and loss of vinculin containing adhesive structures which correlates with acquisition of high motility. Antigen uptake and presentation of native protein antigen was reduced. In contrast, presentation of immunogenic peptides and allostimulatory activity became very efficient and secretion of IL-12 p75 was detectable after antigen presentation. This functional DC maturation ended by apoptotic cell death, and no reversion to the immature phenotype was observed.