Journal of Immunology Research

Review Article

Role of T Regulatory Cells and Myeloid-Derived Suppressor Cells in COVID-19

Table 1

Summary of Tregs in COVID-19 patients with different severities.


	Study groups (number of patients)	Change in Treg levels	Cell phenotype	Notes	Reference no.

Xie et al.	Asymptomatic disease	Decrease	NA	In asymptomatic patients, IL-2 was associated with faster viral clearance and early immune responses.	[54]
Kratzer et al.	Convalescent patients (109) vs. healthy (98)	Decrease	CD25⁺FoxP3⁺	Acute SARS-CoV-2 infection is beneficial by activation of T cells or harmful by reduction of neutrophils.	[51]
Chen et al.	Mild (80)/severe (22) vs. healthy (67)	Increase	CD4⁺CD25⁺CD127^low	CD4⁺ T cells, B cells, IL-6, and IL-10 are indicators of COVID-19 severity.	[47]
Sadeghi et al.	Critical (40) vs. healthy (40)	Decrease	CD4⁺CD25⁺CD127⁻	Imbalanced ratios of Th17/Tregs could play an important role in inflammatory responses and the pathogenesis of the disease.	[52]
Jiménez-Cortegana et al.	Hospitalized (20) vs. healthy (20)	Decrease	CD4⁺CD25^highCD127⁻	M-MDSCs, but not Tregs, could play a role in the immunosuppression shown in COVID-19 patients.	[8]
Patterson et al.	Different severity (224)	Decrease	NA	Decreased Tregs in COVID-19 compared with healthy controls.	[53]
Mohebbi et al.	Different severity (30)	Decrease	CD4⁺FoxP3⁺CD25⁺	Decreased Tregs in COVID-19 patients compared with healthy controls.	[57]
Galván-Peña et al.	Different severity (57)	Increase	CD25⁺FoxP3⁺	Increased Tregs in severe patients is associated with worse outcome.	[43]
Kalfaoglu et al.	Severe	Decrease	NA	In the lung, T cells highly expressed immune-regulatory receptors and CD25, while suppressing expression of FoxP3.	[63]
Qin et al.	Severe (286) vs. non-severe (166)	Decrease	CD4⁺CD25⁺CD127^low		[59]
Neumann et al.	Severe (20) vs. mild/moderate (23)	Increase	IL-10-secreting Tregs		[45]
Wang et al.	Extremely severe (15) vs. severe (20) vs. mild (30)	Decrease	CD45RA⁺ cells	The percentage of natural Tregs was decreased in extremely severe patients.	[61]
Wang et al.	Critical (3) vs. severe (5) vs. mild (4)	Decrease	CD4⁺CD25⁺CD127⁻	Tregs increase during progression from mild to severe then decreased through the progression to critical disease.	[62]
Meckiff et al.	Hospitalized (critical) vs. non hospitalized (mild)	Decrease	NA		[55]
Chen et al.	Severe (11) vs. moderate (10)	Decrease	CD4⁺CD25⁺CD127^low and CD45RA⁺		[60]
Rezaei et al.	Critical (8) vs. severe (27) vs. Moderate (17)	No change	CD4⁺CD25⁺FOXP3⁺		[50]
Rutkowska et al.	Critical (18) vs. severe (23)	Decrease	NA	Percentage of CD45RO⁺CD95⁺ Tregs, among other Treg subsets, was higher in critical compared to severe.	[56]
Ronit et al.	Mechanically ventilated patients (4) with moderate-to-severe COVID-19 ARDS	Increase	FoxP3⁺CTLA-4⁺ Tregs	Increased Tregs with activation markers in the lung.	[46]
Vicket et al.	SARS-CoV-2 (24) vs. RSV (10) vs. Flu (9) vs. Healthy donors (23)	Immune landscape in SARS cov-2 similar to flu or RSV patients	CD25⁺ CD127⁻Foxp3⁺	Only in critical patients, the levels of CD25⁺CD127⁻ FoxP3⁺ cells were increased.	[44]

NA: not available.