en ايمونولوژي Immunology پژوهشي Research <strong>Background</strong>: Vitamin D plays a key role in the modulation of numerous immune functions against infectious agents. We aimed to explore the association between serum 25‑hydroxyvitamin D (25[OH] D) levels and cytokine responses, along with hematological changes, in patients with urinary tract infection (UTI).<br> <strong>Materials and Methods</strong>: Vitamin D level, cytokines (interferon [IFN]&minus;&gamma;, interleukin [IL]&minus;4, IL&minus;6, IL&ndash;10, IL&minus;17A, tumor necrosis factor [TNF]&minus;&alpha;, and transforming growth factor [TGF]&minus;&beta;), hematological indices (neutrophil-to-lymphocyte ratio [NLR], monocyte-to-lymphocyte ratio [MLR], neutrophil-to-monocyte ratio [NMR], platelet-to-lymphocyte ratio [PLR], and mean platelet volume [MPV]), C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR) were evaluated in a case-control human study included 65 patients and 45 controls.<br> <strong>Results</strong>: Among the enhanced cytokine levels in patients, the cytokines IFN-&gamma;, IL-17A, and IL-10 had a significant association with 25(OH)D, but not IL-6, TNF-&alpha;, and TGF-&beta;. The IL-4 levels remained unchanged. By comparing hematological indices, we found the association of increased NLR and MLR with 25(OH)D and the cytokines IFN-&gamma; and IL-17A, along with a decrease in the PLR without showing such an association. The NMR did not show any significant difference. The platelet count showed an association with IL-6, IL-17A, and TGF-&beta;, but the association of MPV with 25(OH)D was significant. The ESR results exhibited statistically non-significant differences. CRP elevation was directly associated with IL-6 and IL-17A, but not with 25(OH)D.<br> <strong>Conclusion</strong>: 25(OH)D-mediated inflammatory cytokine milieu might alter the proportion and function of peripheral blood cells in a regulated manner to support bacterial clearance which needs further studies to be validated. Cytokine, Inflammation, Leukocytes, Platelets, Urinary Tract Infection, Vitamin D 51 60 http://rmm.mazums.ac.ir/browse.php?a_code=A-10-829-3&slc_lang=en&sid=1 Leila Pirdel lpirdel@iauardabil.ac.ir 10031947532846009460 10031947532846009460 Yes Department of Medicine, Ardabil Branch, Islamic Azad University, Ardabil, Iran. Manijeh Pirdel pirdelm@yahoo.com 10031947532846009461 10031947532846009461 No Department of Midwifery, Astara Branch, Islamic Azad University, Astara, Iran.