Extracorporeal phototherapy is a cell immunotherapy that has inhibitory and stimulatory effects which enables its use in the treatment of graft versus host disease as well as cutaneous T-cell lymphoma. The process is performed in three stages: leukapheresis, photoactivation of collected cells with 8‐methoxypsoralen (8‐MOP)/UVA which later triggers apoptosis of cells and re‐infusion of treated cells into the patients' bloodstream. The cells thus treated therefore constitute a medicinal product or, more precisely advanced therapy medicinal product. During the preparation of the cell product imunosupresive and imunostimulatory cell components are generated. Monocytes activated during the extracorporeal phototherapy induce efector immune responses in the patient’s organism and therefore represent the immunostimulatory component of the cell product. Our purpose was to develop a standardized protocol for the in vitro treatment of cells with compounds that inhibit monocyte activation and thereby to make the first step towards the optimization of the extracorporeal phototherapy for treatment of graft versus host disease.
We studied the effect of dexamethason on differentiation and maturation of human monocytes in a culture of mononuclear cells isolated from the blood of healty blood donors. We treated mononuclear cells with 28 to 558 µg/ml dexamethason for 24 or 48 hours. Then we activated them with stimulants: LPS (1 µl/ml) + IFNγ (0,5 µl/ml), mCD40L (2 µl/ml), mCD40L (2 µl/ml) + IFNγ (0,5 µl/ml) and R848 (1 µl/ml). Only LPS+IFNγ and R848 proved to be appropriate stimulants for use in our experimental model, as with the rest we haven't acquired the relevant positive control. Cells treated with dexamethason expressed lower levels of co-stimulatory molecules CD40, CD80, CD83 and CD86 as untreated cells. Treated cells expressed lower levels of co-stimulatory molecules than untreated cells even after exposure to LPS+IFNγ. We were unable to evaluate the effect of dexamethason on the expression of inhibitory molecules ILT-3, ILT-4 and PD-L1 due to the lack of repeatability. Dex decreased the capacity of treated monocytes for excretion of inflammatory cytokines (IL-8, IL-1β, IL-6, TNFα, IL-12p70) as well as anti-inflammatory cytokine IL-10 after activation with LPS+IFNy or R848.
In conclusion, our data suggest that dexamethason partially inhibits differentiation and maturation of monocytes.
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