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To elicit an immune response, dendritic cells, DCs, present an antigen displayed with MHC class-II and the co-stimulatory molecules CD80 and CD86. Based on immune response characteristics, they are subdivided into immature, mature, and tolerogenic DCs.
To generate various dendritic cell subsets in vitro, begin with a multi-well plate containing human monocytes — immune precursor cells in a complete medium containing growth factors and the cytokine IL-4 — a signaling molecule.
Incubate the cells for a prolonged duration. The growth factors and IL-4 induce monocyte proliferation and differentiation into immature DCs.
Immature DCs possess pattern recognition receptors, PRRs, and express low MHC class-II and co-stimulatory molecules, exhibiting a diminished capacity to elicit an immune response.
Treat one well containing immature DCs with immunomodulatory agents — vitamin D3 and glucocorticoids. These immunomodulatory agents downregulate MHC class-II and co-stimulatory molecules' expression. This leads to differentiation into tolerogenic DCs — immuno-regulatory cells that prevent exaggerated or undesirable immune responses.
Treat another well containing immature DCs with lipopolysaccharide, LPS — an antigen. LPS interacts with cells' toll-like receptor-4 — a PRR, initiates a signaling cascade, and differentiates them into mature cells. These cells express high MHC class-II, co-stimulatory molecules, and PRRs — efficient for antigen processing and presentation.
Observe the differentially-treated wells for distinct morphological characteristics representing the dendritic cell subtypes.
Seed four sets of CD14+ monocytes in a concentration of 0.3 to 0.5 x 106 per milliliter of cell culture medium of IL-4 in six-well plates. Incubate the cells in a tissue culture incubator at 37 degrees Celsius with 5% CO2. On day 4, remove 850 microliters of medium from the culture, and centrifuge.
Aspirate the supernatant, and resuspend the pellet in 1 milliliter of cell culture medium. Add the cell mixture back to the culture. On day 5, add 1 microliter of vitamin D3 stock and 1 microliter of dexamethasone stock per milliliter of medium to two of the sets to generate tolerogenic moDCs.
On day 6, add 200 nanograms per milliliter of GM-CSF and 200 nanograms per milliliter of IL-4 to all of the sets. Add 1 microgram per milliliter of LPS to one of the sets treated with only GM-CSF and IL-4 to generate mature moDCs.
Add 1 microgram per milliliter of LPS to one set of the tolerogenic modes moDCs to generate LPS-tolerogenic moDCs. Finally, on day 7, harvest the different types of moDCs by flushing the culture dish with PBS-EDTA.