Figure 3. Loss of germinal center type Bcl-6+ T follicular helper cells in COVID-19 lymph nodes and spleens.

(A) Representative multi-color immunofluorescence image of CD4 (red), CXCR5 (green) and DAPI (blue) staining in lymph nodes from early (left) and late (middle) COVID-19 patients and controls (right). Arrows indicate CD4⁺ CXCR5⁺ T_FH cells. (B) Representative multi-color immunofluorescence images of CD4 (red), Bcl-6 (white) and DAPI (blue) staining in lymph nodes from early (left) and late (middle) COVID-19 patients and controls (right). Arrows indicate CD4⁺ Bcl-6⁺ GC-type T_FH cells. (C) Representative multi-color immunofluorescence image of CD4 (red), CXCR5 (green) and DAPI (blue) staining in spleens from early (left) and late (middle) COVID-19 patients and controls (right). (D) Representative multi-color immunofluorescence image of CD4 (red), Bcl-6 (white) and DAPI (blue) staining in spleens from early (left) and late (middle) COVID-19 patients and controls (right). (E and F) Relative proportions of CD4⁺ CXCR5⁺ T_FH cells (E) and CD4⁺ Bcl-6⁺ GC-type T_FH cells among CD4⁺ T cells (F) in lymph nodes from early (purple) (n = 5) and late (blue) (n = 6) COVID-19 patients and controls (green) (n = 10). (G and H) Relative proportions of CD4⁺ CXCR5⁺ T_FH cells (G) and CD4⁺ Bcl-6⁺ GC-type T_FH (H) among CD4⁺ T cells in spleens from early (purple) (n = 4) and late (blue) (n = 6) COVID-19 patients and controls (green) (n = 7). Multiple comparisons are controlled for by Kruskal-Wallis test. Error bars represent mean ±SEM. *p < 0.05; **p < 0.01.