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Published on: March 8, 2024
Circulating Cytokines and Lymphocyte Subsets in Patients Who Have Recovered from COVID-19
Hasichaolu1, Xinri Zhang2, Xin Li3
1Department of Laboratory Medicine, First Hospital of Shanxi Medical University, Taiyuan 030001, China.
Insights
COVID-19 survivors show reduced lymphocyte counts and elevated cytokines two weeks post-recovery. These immune changes predict rehabilitation, but sustained inflammation necessitates continued medical monitoring.
Area of Science:
- Immunology
- Infectious Diseases
- Virology
Background:
- COVID-19 infection can significantly impact immune cell populations and cytokine profiles.
- Understanding post-infection immune status is crucial for assessing recovery and long-term health outcomes.
Purpose of the Study:
- To evaluate the immune status of individuals two weeks after recovering from COVID-19.
- To analyze circulating cytokine and lymphocyte subset levels in post-COVID-19 patients compared to healthy controls.
Main Methods:
- Flow cytometry was used to measure lymphocyte subsets (total lymphocytes, CD3+, CD4+, CD8+ T cells, CD19+ B cells, CD56+ NK cells).
- Serum concentrations of key cytokines (IL-1, IL-4, IL-6, IL-8, IL-10, TGF-β, TNF-α, IFN-γ) were quantified.
- Receiver Operating Characteristic (ROC) curve analysis was employed to identify predictors of rehabilitation efficacy.
Main Results:
- Post-COVID-19 patients exhibited lower levels of most lymphocyte subsets compared to healthy controls.
- Elevated levels of several cytokines, including IL-2, IL-4, IL-6, IL-10, TNF-α, IFN-γ, and IL-17, were observed in recovered patients.
- Positive correlations between T cells, B cells, and specific cytokines were found in post-recovery patients but not in controls.
- Decreased lymphocyte counts and increased cytokine levels independently predicted rehabilitation efficacy.
Conclusions:
- The immune system undergoes gradual recovery after COVID-19, but a hyperinflammatory state can persist for over 14 days.
- Continued medical observation is recommended for discharged patients due to sustained immune alterations.
- Longitudinal studies are essential to fully elucidate the long-term consequences of COVID-19 infection on the immune system.
Abstract:
To investigate the immune status of people who previously had COVID-19 infections, we recruited two-week postrecovery patients and analyzed circulating cytokine and lymphocyte subsets. We measured levels of total lymphocytes, CD3+ T cells, CD4+ T cells, CD8+ T cells, CD19+ B cells, and CD56+ NK cells and the serum concentrations of interleukin- (IL-) 1, IL-4, IL-6, IL-8, IL-10, transforming growth factor beta (TGF-β), tumor necrosis factor alpha (TNF-α), and interferon gamma (IFN-γ) by flow cytometry. We found that in most postrecovery patients, levels of total lymphocytes (66.67%), CD3+ T cells (54.55%), CD4+ T cells (54.55%), CD8+ T cells (81.82%), CD19+ B cells (69.70%), and CD56+ NK cells (51.52%) remained lower than normal, whereas most patients showed normal levels of IL-2 (100%), IL-4 (80.88%), IL-6 (79.41%), IL-10 (98.53%), TNF-α (89.71%), IFN-γ (100%), and IL-17 (97.06%). Compared to healthy controls, two-week postrecovery patients had significantly lower absolute numbers of total lymphocytes, CD3+ T cells, CD4+ T cells, CD8+ T cells, CD19+ B cells, and CD56+ NK cells, along with significantly higher levels of IL-2, IL-4, IL-6, IL-10, TNF-α, IFN-γ, and IL-17. Among postrecovery patients, T cells, particularly CD4+ T cells, were positively correlated with CD19+ B cell counts. Additionally, CD8+ T cells were positively correlated with CD4+ T cells and IL-2 levels, and IL-6 positively correlated with TNF-α and IFN-γ. These correlations were not observed in healthy controls. By ROC curve analysis, postrecovery decreases in lymphocyte subsets and increases in cytokines were identified as independent predictors of rehabilitation efficacy. These findings indicate that the immune system gradually recovers following COVID-19 infection; however, the sustained hyperinflammatory response for more than 14 days suggests a need to continue medical observation following discharge from the hospital. Longitudinal studies of a larger cohort of recovered patients are needed to fully understand the consequences of the infection.
