Imbalance of effector memory CD3+CD4+ Th cell subsets in patients with COVID-19. Scatter plots showing the relative count of the main “polarizes” Th cell subsets within the total central memory CD45RA−CD62L– Th cells, including Th1 (CXCR5-CXCR3+CCR6-CCR4-) (a), Th2 (CXCR5-CXCR3-CCR6-CCR4+) (b), total Th17 (CXCR5-CCR6+) (c), and CXCR5-positive Tfh cells (d), respectively, in peripheral blood samples from patients with 25(OH)D > 11.4 ng/mL (black circles), patients with 25(OH)D ≤ 11.4 ng/mL (black triangles), and HC subjects (black squares). Numbers represent the percentage of the indicated Th cell subset among the total lymphocyte population.