CCL2 and COVID-19: Recently, Xiong et al. utilized the RNA-Seq approach to depict the transcriptional features of bronchoalveolar lavage fluid (BALF) and peripheral blood mononuclear cell (PBMC) samples of COVID-19 patients and found key cytokines such as CCL2/MCP-1, CXCL10/IP-10 and CCL3/MIP-1A were excessively released in COVID-19 [5].