FLT3LG and COVID-19: A gradient-boosted machine classifier model and SHAP metrics reinforced the distinct importance of profibrotic growth factors and neutrophil and Th17 mediators in the SARS-CoV-2 host response, with higher concentrations of EGF, PDGF-AA, FLT-3L, and IL-8, and lower concentrations of IL-27 as top drivers of COVID-19 diagnosis (Fig. 7c, d).