The immune cells profiles of individuals with sulfur mustard-induced serious long-term respiratory complications

•SM-exposed patients showed significant decreases in average FVC, FEV1, DLCO, MMEF, and PEF values.•The mean values for RV, RV/TLC ratio, and RAW ratio showed a marked increase in SM-exposed patients.•Long-term SM exposure increases WBC and lymphocyte counts while decreasing regulatory T cell subsets.•A negative correlation exists between some leukocyte populations and lung function.•Our findings show SM-induced long-term changes in immune dynamics from impaired inflammation regulation. Sulfur mustard (SM) induced pulmonary disorder is a heterogeneous disease characterized by uncontrolled inflammatory immune responses. In this cross-sectional study carried out in Isfahan-Iran, our objective was to thoroughly evaluate the clinical health and peripheral blood leukocyte profiles of adult veterans exposed to SM 25–30 years. In total, 361 people were studied in two groups, 287 chemical veterans with pulmonary complications and 64 healthy individuals as a control group. The participants underwent a comprehensive lung evaluation, including physical examination, Pulmonary Assessment, and Spirometry Assessment. Blood samples were collected in EDTA-treated tubes and flow cytometry analysis was employed to study different population of leukocytes including lymphocytes, monocytes, and natural killer cells. In our results, SM-exposed patients showed a significant increase in mean WBC and lymphocyte absolute count. However, the frequency of CD14+ monocytes and CD3+ CD4+ CD25+Hi as regulatory T cell subsets significantly decreased in SM-exposed patients. In addition, there was a negative correlation between CD45+ CD14+ cells and residual volume (RV). The population of NK cells showed a negative correlation with forced expiratory volume in the first one second to the forced vital capacity (FEV1/FVC). On the other hand, the percentage of CD19+ B cells positively correlated with Mid-maximum expiratory flow (MMEF) rate, ppm Reading, Carboxyhemoglobin (CoHb), and FEV1, and it was negatively correlated with airway resistance (RAW). Evaluation of CD3+ CD8+ cytotoxic T cells frequency negatively correlated with CoHb, ppm Reading, total lung capacity (TLC), and RV. Furthermore, the count of CD3+ CD4+ T cells demonstrated a negative correlation with TLC. The percentage of CD3+ CD4+ CD25+ cells was positively correlated with ppm reading and CoHb. Overall, our findings revealed modifications in total lymphocyte dynamics and a decrease in the percentage and absolute number of regulat