The sIgA is capable of inducing the synthesis of IL-6, IL-8, monocyte chemoattractant protein-1 (MCP-1), and the granulocyte–macrophage colony-stimulating factor (GM-CSF) in the lung fibroblasts [120], which leads to hypothesizing its participation in severe cases of COVID-19 [121]. Here, CCL2 is linked to COVID-19.