CXCL13 and COVID-19: Distinguishing patients with severe and moderate COVID-19, seven proteins were significantly altered (>1 NPX mean difference) (Table 2) including CXCL13 and C-X-C motif chemokine ligand 9 (CXCL9), where TNF receptor superfamily member 12A (TNFRSF12A) was the most increased (Figure 1), highlighting the involvement of the TNF-a pathway.