We further confirmed that anti-COVID-19 and anti-asthma effects performed by luteolin were mainly directed through immunomodulatory, antioxidant, antiviral, and anti-inflammatory signaling pathways, including Toll-like receptor signaling pathway, MAPK signaling pathway, PD-L1 expression and PD-1 checkpoint pathway in cancer, TNF signaling pathway, apoptosis, PI3K–AKT signaling pathway, EGFR tyrosine kinase inhibitor resistance, ErbB signaling pathway, HIF-1 signaling pathway, AGE/RAGE signaling pathway, and so on. This evidence concerns the gene CD274 and COVID-19.