Characteristics of lymphocyte subsets and inflammatory factors in patients with COVID-19

Objective: This research aims to examine the involvement of lymphocyte subsets and inflammatory cytokines in the development and progression of COVID-19. Methods: 164 COVID-19 patients were admitted to hospital between December 2022 and January 2023. Based on lung CT scans and whether it is necessary for intensive care unit (ICU) admission, they were categorized into: severe groups (84) and mild disease groups (80). Peripheral blood were also collected from 101 healthy examinees and 164 patients. Flow cytometry (FCM) was used to measure the absolute and relative counts of lymphocyte subsets, while chemiluminescence was used to detect the level of inflammatory cytokines. Results: The COVID-19 patient group exhibited lower count of lymphocytes subsets than healthy control group. Moreover, COVID-19 patient case presented higher content of cytokines (IL-6, IL-4, IL-8, IL-10, and TNF-α) expression compared to healthy control case. Within the COVID-19 patient group, individuals with severe disease showed lower counts of lymphocytes subsets than the mild disease case. Furthermore, IL-6 levels in severe case were higher than the mild disease patients case. Multi-variate logistic regression analysis confirmed IL-6 (odds ratio: 0.985 [0.977–0.993]), CD3+ T cells (odds ratio:1.007 [1.004–1.010]), CD8+ T cells (odds ratio:1.016 [1.009–1.023]), and CD19+ B cells (odds ratio:1.011 [1.002–1.020]) independently predicted severe progression. ROC curve results indicated AUC for lymphocytes in patients with severe COVID-19 was 0.8686 (0.8112–0.9260), CD3+ T cells was 0.8762 (0.8237–0.9287), CD8+ T cells was 0.7963 (0.7287–0.8638), CD4+ T cells was 0.8600 (0.8036–0.9164), CD19+ B cells was 0.7217 (0.6434–0.8001), NK cells was 0.6492 (0.5627–0.7357), age was 0.6699 (0.5877–0.7521), diabetes was 0.5991 (0.5125–0.6857), and IL-6 was 0.7241 (0.6479–0.8003). Furthermore, the ROC curves for different factors (CD3+ T cells, age, IL-6) yielded an AUC of 0.9031 (0.8580–0.9483). Conclusions: The research indicated that COVID-19 patients experience a decrease in lymphocytes subset and an increase in the inflammatory factor IL-6, particularly in the severe case group. As a result, the count of lymphocyte subset (CD3+ T cells) and the content of inflammatory cytokine (IL-6) can serve as predictive markers for assessing the severity of COVID-19 and developing treatment plans efficacy.