Influence of extracorporeal photopheresis on lymphocytes subpopulations in peripheral blood of patients with chronic graft-versus-host disease

Summary

Introduction

Currently, extracorporeal photopheresis (ECP) occupies a confident position in the therapy of patients after allogeneic hematopoietic stem cell transplantation (allo-HSCT), as a part of the treatment in acute and chronic graft-versus-host disease (cGVHD). ECP has an immunomodulatory effect consisting in elimination of immune cells involved in the cGVHD pathogenesis. However, the effect of ECP on the patients’ lymphocytes remains unclear. The aim of present study was to determine absolute counts of T-helper (Th) cells, cytotoxic T-lymphocytes (CTL), B- and NK-cells in peripheral blood of chronic GVHD (cGVHD) patients undergoing ECP.

Patients and methods

Blood samples of ten patients with hematological malignances after allo-HSCT with an extensive form of cGVHD (6 women, 4 males, median age of 45 years old) were subject to examination. The study of lymphocyte subpopulations was carried out before the first ECP procedure, and after four ECP procedures (a one-month course). Absolute counts of T-helper cells (CD3+/CD4+), cytotoxic T cells (CD3+/CD8+), B cells (CD19+) and NK cells (CD3-/CD56+) were determined by flow cytometry (BD FACS Canto II). Wilcoxon signed-rank test was used to determine differences in lymphocytes subpopulations before and after ECP procedures. Statistical processing of data was carried out using GraphPad Prism.

Results

Before performing ECP, Th count was above the reference range in 4 patients (40%), CTL count in 9 (90%), B-cell count, in 4 (40%) and NK-cell count, in 6 cases (60%). After the 4 ECP procedures, 3 out of 4 patients reached normal Th-cell counts. Six out of 8 patients showed reduction of CTL and approached the reference interval. Numbers of NK-cells reduced and reached normal values in 5 patients. Reduction of the B сell amounts did not occur. Upon analysis of absolute number of different lymphocyte subpopulations, a statistically significant decrease after ECP courses was observed for CTLs (Table. 1), regardless of CTL number before ECP.

Conclusion

It was shown in our study that, after 4 ECP procedures, there was a significant decrease in absolute amounts of cytotoxic T-cells, whereas no significant change in T-helper cells, B-cells, or NK-cells was observed. It is necessary to continue research in larger cohorts of patients.

Keywords

Extracorporeal photopheresis, graft-versus-host disease, allogeneic hematopoietic stem cell transplantation, lymphocytes subpopulations, flow cytometry.