To investigate the expression of peripheral T lymphocyte subsets of patients with coronavirus disease 2019 (COVID-19).

Total of 93 patients with COVID-19 admitted to Infection Department of the Fifth Affiliated Hospital of Sun Yat-Sen University from January 2020 to March 2020 were selected as research group, while 92 healthy follow-up individuals from April 2019 to March 2020 were randomly selected as control group. The levels of peripheral blood white blood cell (WBC), lymphocytes, CD3+ T, CD4+ T and CD8+ T lymphocytes were compared between the two groups. According to the clinical classification criteria in "New Coronavirus Pneumonia Diagnosis and Treatment Plan (Trial Seventh Edition)" , patients with COVID-19 were divided into mild group, ordinary group, severe group and critical group. WBC, lymphocytes, CD3+ T, CD4+ T and CD8+ T lymphocytes were compared between each group at admission and at two weeks after admission, and the correlation between above the indexes and severity of the disease was analyzed by Spearman correlation coefficient, respectively.

Lymphocytes (t = 3.94, P < 0.001), CD3+ T (t = 3.33, P = 0.001), CD4+ T (t = 3.73, P < 0.001), CD8+ T (t = 2.18, P = 0.031) lymphocytes in COVID-19 patients were significantly lower than those in control group. Leukocytes of the patients with COVID-19 [(5.38 ± 2.97) × 109/L] was lower than that of control group [ (5.92 ± 1.16) × 109/L], but with no significant difference (t = 1.23, P = 0.222). Leukocytes of 93 patients with COVID-19 at two weeks after treatment were significantly higher than those at admission [(5.90 ± 1.96) × 109/L vs. (5.38 ± 2.97) × 109/L)], with significant difference (t =-3.47, P = 0.001), but there were no significant differences in lymphocytes and T lymphocyte subsets (all P > 0.05). The levels of leukocyte, T lymphocyte, CD3+ T, CD4+ T and CD8+ T lymphocytes at admission varied depending on the severity of the disease, and were negatively correlated with disease severity (all P < 0.05). The levels of T lymphocyte, CD3+ T and CD8+ T cell at two weeks of treatment were statistically different in patients with different clinical types, and were also negatively correlated with the severity of the disease (all P < 0.05).

There were imbalance expression of T lymphocyte subsets in patients with COVID-19, which were negatively correlated with the severity of the disease. The detection of peripheral T lymphocyte subsets was of great significance for the diagnosis and severity evaluation of COVID-19.