Fig. 4: Cellular recruitment of Tfh cell, plasmablasts, and monocytes.

Early (< day 14) recruitment of innate and adaptive cells was measured by flow cytometry (see Supplementary Figure 3 for gating strategy) for COVID-19 children (n = 22), adults (n = 13), and negative controls (n = 10) (a–e). Convalescent/ memory samples of children (n = 15), adults (n = 15), and negative adults (n = 15) were also tested alongside negative children (n = 15) (f–j). Total monocytes (a, f), monocyte phenotype (b, g), and activation of monocytes (c, h). Total plasmablast (d, i) and activated T follicular helper cell (e, f). Data represents the individual response, mean ± SD. Statistical differences were determined using a two-sided Mann–Whitney test between children and adults, adults and negative adults, and children and negative children where **p < 0.01, ***p < 0.001, ****p < 0.0001. a ***p = 0.0002, (b) **p = 0.0054, ***p = 0.0001, ****p < 0.0001, (c) **p = 0.0020, ****p < 0.0001, (d) ***p = 0.0001, (e) ****p < 0.0001, (g) *p = 0.0321, (h) *p = 0.0203, **p = 0.0086, (i) *p = 0.0124, **p = 0.0016, (j) *p = 0.0489, 0.0235, **p = 0.0013, ***p = 0.0004.