Tehran University of Medical Sciences Iranian Journal of Allergy, Asthma and Immunology 1735-1502 0 0 2026 02 11 1 17 EN Azadeh Roostaee Department of Biology, Marv.C., Islamic Azad University, Marvdasht, Iran Ramin Yaghobi Transplant Research Center, Shiraz University of Medical Sciences, Shiraz, Iran Afsoon Afshari Nephro-Urology Research Center, Shiraz University of Medical Sciences, Shiraz, Iran Mojtaba Jafarinia Department of Biology, Marv.C., Islamic Azad University, Marvdasht, Iran 2025 06 09 2025 11 09 Human cytomegalovirus (HCMV) is a frequent complication in kidney transplant recipients (KTRs), often impacting immune regulation. TH9 cells, a subset of CD4+ T cells, are characterized by their secretion of interleukin-9 (IL-9). This study aimed to analyze the phenotypic profile of TH9 cells and their associated cytokine expression in KTRs, and to evaluate mRNA levels of IL-4 and transforming growth factor-β (TGF-β), key cytokines involved in TH9 differentiation. Ten HCMV+ and 10 HCMV− KTRs, along with 10 age- and sex-matched healthy controls, were enrolled. HCMV viral load was quantified using TaqMan real-time polymerase chain reaction. Flow cytometry was used to assess surface markers (CCR6+CCR4−IL-4Rα+CD4+) and intracellular IL-9 expression in TH9 cells. Gene expression levels of IL-4 and TGF-β were also assessed. Surface staining revealed a significantly higher frequency of CD4+CCR4− and CD4+CCR6+ T cells in HCMV− KTRs compared to HCMV+ patients. Conversely, the overall frequency of CD4+ TH9 cells was elevated in HCMV+ KTRs. Intracellular staining demonstrated a significant increase in CD4+IL-9+ and CD4+IL-4Rα+ T cells in the HCMV+ group. Additionally, mRNA expression levels of IL-4 and TGF-β were markedly higher in HCMV+ KTRs than in HCMV− counterparts. These findings suggest a potential role for TH9 cells and their signature cytokine IL-9 in the antiviral immune response in KTRs. While TH9 cells may contribute to HCMV-related immune modulation, further research is needed to fully elucidate their protective mechanisms against viral infections.   Keywords: ; ; ;    https://ijaai.tums.ac.ir/index.php/ijaai/article/view/4485 https://ijaai.tums.ac.ir/index.php/ijaai/article/download/4485/2308