Dynamics of peripheral immune cells and their HLA‐G and receptor expressions in a patient suffering from critical COVID‐19 pneumonia to convalescence

OBJECTIVES: Host immune responses are indispensable to combat the disease. We report the dynamics of peripheral immune cells, cytokines, and human leucocyte antigen‐G (HLA‐G) and its receptor expressions in a patient suffering from critical COVID‐19 pneumonia to convalescence. METHODS: Clinical data of the patient were collected from medical records. The expressions of HLA‐G and receptors ILT2, ILT4 and KIR2DL4 in peripheral immune cells were measured with flow cytometry. RESULTS: From critical COVID‐19 to the convalescent stage, early lymphopenia was improved (median: 0.6 × 10(9) L(−1) vs. 0.9 × 10(9) L(−1), P = 0.009), and an obvious fluctuation in WBC and neutrophil counts was observed. Initially, low levels of CD4(+) T cells (from 120 to 528 μL(−1)) and CD8(+) T cells (from 68 to 362 μL(−1)) gradually increased to normal levels. Meanwhile, high IL‐6 (from 251.8 to 6.32 pg mL(−1)), IL‐10 (from 39.53 to 5.21 pg mL(−1)) and IFN‐γ (from 13.55 to 3.16 pg mL(−1)) levels decreased, and IL‐4 (from 2.36 to 3.19 pg mL(−1)) and TNF‐α (from 2.27 to 20.2 pg mL(−1)) levels increased quickly when the viral RNA returned negative. Moreover, the percentage of HLA‐G(+) T cells, B cells and monocytes follows high–low–high pattern, while the percentage of receptors ILT2‐, ILT4‐ and KIR2DL4‐expressing cells remained relatively stable. CONCLUSION: Our findings provide valuable information on the dynamics of early peripheral immunological responses in SARS‐CoV‐2 infection. CD4(+) and CD8(+) T cells, cytokines and HLA‐G(+) immune cells are associated with the natural history of the critical COVID‐19 patient; however, future studies are necessary.