Figure 1. Peripheral CD4⁺ T cell subsets in COVID-19 convalescent patients.

Blood samples were collected from COVID-19 convalescent patients (n = 13) and healthy individuals (n = 13). PBMCs were isolated for antibody staining and FACs phenotyping of CD4⁺ T cells. (A) Gating strategies on naive CD4⁺ T cells (CD45RA⁺CCR7⁺), central-memory CD4⁺ T cells (CD45RA^–CCR7⁺), and effector-memory CD4⁺ T cells (CD45RA^–CCR7^–). (B) Statistical analysis of the frequency of CD4⁺ Tnaive, CD4⁺ Tcm, and CD4⁺ Tem cells between healthy individuals and COVID-19 convalescent patients. (C) Gating strategies on different peripheral circulating CD4⁺ T cell subsets, including CD25^–CD45RA^–CXCR5⁺ cTfh cells, CCR7^hiPD-1^– central-memory cTfh (cTfh-cm) cells, CCR7^loPD-1⁺ effector-memory cTfh (cTfh-em) cells, CXCR3⁺CCR6^– cTfh (cTfh1) cells, CXCR3^–CCR6^– cTfh (cTfh2) cells, and CXCR3^–CCR6⁺ cTfh (cTfh17) cells. Within CD3⁺CD8^–CD4⁺ circulating T cells, Th1 cells were defined as CD25^–CD45RA^–CXCR3⁺CCR6^– cells, Th2 cells as CD25^–CD45RA^–CXCR3^–CCR6^– cells, and Th17 cells as CD25^–CD45RA^–CXCR3^–CCR6⁺ cells. Circulating Treg cells were defined as CD25⁺CD45RA^–CD127^– cells and cTfr cells as CD25⁺CD45RA^–CD127^–CXCR5^hiPD-1^hi cells. (D) FACs plot showing the representative cTfh-cm and cTfh-em cells between healthy individuals and COVID-19 convalescent patients. Quantifications on the frequency of these cells within cTfh cells (E) and CD4⁺ T cells (F). (G) Frequency of cTfh1, cTfh2, and cTfh17 cells within cTfh cells in healthy individuals and COVID-19 convalescent patients. (H) Statistical analysis showing the differences of the frequencies of Treg and cTfr cells between healthy individuals and COVID-19 convalescent patients, and the same analysis on Th1, Th2, and Th17 cells (I). (J) Histogram showing the PD-1 expression on Th1, Th2, and Th17 cells between healthy individuals and COVID-19 convalescent patients. HC, healthy control individuals (n = 13); CP, COVID-19 convalescent patients (n = 13). Each dot represents an individual subject. Bars represent the mean values. *P < 0.05 and **P < 0.01 by unpaired and 2-tailed Student’s t test.