Extracorporeal photopheresis as an immunomodulatory agent: Haematocrit‐dependent effects on natural killer cells

Abstract

The GvHD is a major cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HSCT). Extracorporeal photopheresis (ECP) represents an alternative therapeutic strategy to immunosuppressive therapy. Although ECP is used since 1990s, the mechanism of action has not yet been completely clarified. We analyzed cells collected from 20 ECP procedures of 4 patients affected by chronic GvHD and, for comparison, Peripheral Blood Mononuclear Cells (PBMCs) of 10 healthy donors undergoing from same type of photochemiotherapy, evaluating by flow cytometry, the effects before and after photoactivation with 8-MOP. The analysis showed a significant increase in cell death after ECP in particular in CD4 T lymphocytes as described in literature correlated with haematocrit value. Most interesting data emerge from the analysis of cytotoxic activity of NK cells, using flow cytometry analysis of surface expression of CD107a in the presence of target cells (K562). In all analyzed samples it was possible to document a statistically significant reduction of the cytotoxic activity of NK cells after photoactivation. The decrease of the cytotoxic activity was related to hematocrit value of leukoapheresis: in fact, lower HCT values were associated with a more marked reduction of cytotoxic activity. The study confirms literature data about the increase of cellular mortality induce by ECP. Furthermore, for the first time it is demonstrated that the ECP exerts a marked and significant inhibitory effect on the cytotoxic activity of NK cells. Our study suggests that lower values of hematocrit are associated with better treatment outcome.

Apoptosis induction by extracorporeal photopheresis is enhanced by increasing the 8‐methoxypsoralen concentration and by replacing plasma with saline

“…The therapeutic action of ECP relies on apoptosis. 4,[15][16][17][18][19] The concept is that more apoptosis would translate to higher efficacies. However, ECP relies also on cell interactions.…”

“…The therapeutic action of ECP relies on apoptosis 4, 15–19 . The concept is that more apoptosis would translate to higher efficacies.…”

“…12 Furthermore, antigen-presenting cells (APC) suppress T-cell effector activity and support regulatory T-cell (Treg) function. 13,14 Apoptosis induction is a central mechanism of ECP, 4,[15][16][17][18][19] and several factors influence the efficacy of 8-MOP/UVA treatment (see Figure 1). In general, the two standard starting concentrations of 8-MOP used for photopheresis are 200 ng/ml for offline ECP, and 340 ng/ml for inline ECP (calculated as product volume  0.017 according to the instruction for use of Uvadex, Therakos).…”

Extracorporeal photopheresis in solid organ transplantation

“…После реинфузии фрагменты апоптотических лимфоцитов поглощаются незрелыми дендритными клетками, которые впоследствии созревают в антигенпредставляющие клетки [5,137,139,140]. Этот каскад оказывает различные иммуномодулирующие эффекты, опосредованные смещением цитокинового профиля с Th1 на Th2 [4], что характеризуется увеличением противовоспалительных и снижением провоспалительных цитокинов, а также снижением цитотоксической способности естественных киллерных клеток и увеличением толерогенных Treg [141][142][143]. Так, у 23 реципиентов трансплантата сердца при применении ЭКФ в качестве профилактики реакции отторжения наблюдался сдвиг цитокинового профиля в сторону повышения противовоспалительных цитокинов [133].…”

Extracorporeal Photopheresis for Bronchiolitis Obliterans Syndrome After Lung Transplantation

“…[22][23][24]29,30 This cascade exerts various immunomodulatory effects mediated via an increase in anti-inflammatory cytokines, a decrease in proinflammatory cytokines, a decrease in the cytotoxic capacity of natural killer cells, an increase in neutrophil granulocyte apoptosis, and an increase in tolerogenic regulatory T (T reg ) cells. [31][32][33][34] Additionally, ECP induces the differentiation of monocytes into immature dendritic cells that produce substantial amounts of the anti-inflammatory cytokine interleukin-10. 35 Most of the studies reviewed here have used a THERAKOS photopheresis system.…”