Objective: T helper 22 (Th22) and T helper 17 (Th17) cells that are especially a subtype of CD4+ T lymphocyte are known to secrete interleukin 22 (IL-22). Th22 cells have been reported to play a role in infection, chronic inflammation, tumor development, autoimmune disease pathogenesis, and cell development. However, the role and number of cells whose carrying IL-22 in patients with hematopoietic stem cell transplantation is unknown. In this study, the number of circulating cells carrying IL-22, IL-17A, TNF-α and IFN-γ were investigated before hematopoietic stem cell transplantation (at stem cell infusion day) and during engraftment.

Methodology: A total of 10 patients who underwent autologous or allogeneic hematopoietic stem cell transplantation consecutively at the Department of Stem Cell Transplantation at Akdeniz University School of Medicine between July and December 2019 and 10 healthy people as a control group were included in this study. After separating the peripheral blood mononuclear cells (PBMCs) from the peripheral blood both at the transplantation day (before stem cell infusion) and at the engraftment, PBMCs were incubated by phorbol myristate acetate (PMA), ionomycin and monensin for 4h. After that, the number of absolute lymphocytes carrying IL-22, IL-17A, TNF-α and IFN-γ among CD3 and CD4 double-positive T cells were determined by flow cytometry in patient and control groups, respectively.

Results: The diagnosis of patients’ were multiple myeloma (6/10), B cell acute lymphoid leukemia (1/10), acute myeloid leukemia (1/10), non-hodgkin lymphoma (1/10), and gestational trophoblastic disease (1/10), respectively. While 6 of patients (‘) had autologous stem cell transplantation, 4 patients (@) had allogeneic stem cell transplantation. The number of absolute lymphocytes carrying IL-22, IL-17A, TNF-α and IFN-γ was found significantly lower in the patient group compared with the control group as shown in Table 1. In the patient group, although, there was no statistically significant difference between them, the number of absolute lymphocytes carrying IL-22, IL-17A, TNF-α and IFN-γ at engraftment were higher than stem cell infusion day (D0). Table 1 The absolute count of lymphocytes carrying IL-22, IL-17A, TNF-α and IFN-γ at stem cell infusion day (D0).

Conclusion: In our study, we detected that the number of absolute lymphocytes carrying IL-22, IL-17A, TNF-α and IFN-γ at stem cell infusion day (D0) were significantly lower in the patient group compared with control group. This might be related with previous received treatments including conditioning regimen, chemotherapy or radiotherapy. In addition to, although there was a trend increased the absolute count of lymphocytes carrying IL-22, IL-17A, TNF-α and IFN-γ at engraftment in the patient group, there was no significant difference between D0 and engraftment. This could be related to small sample size as well. In conclusion, we think that further larger prospective studies are needed to clarify for this issue in patients with hematopoietic stem cell transplantation.