When we analyzed functional enrichment in this gene cluster using the Toppgene internet application [16], we discovered that, in mild cases of COVID-19, CD68+  cells with high levels of PSMB8 appear to demonstrate enrichment in functions such as defense response (comprising PSMB8, CD68, GRN, APOE, FN1, MDK, NUPR1, IFIT2, MARCO, HLA-DQA2,CAPG, FABP4, and TUBB) and lipid homeostasis (lipid transport and lipid catabolism: APOC1, APOE, CES1, PLD3, FABP4, CES1, PLIN2, FABP4, RBP4, and CYP27A1) (Fig. 4F). Here, TUBB is linked to COVID-19.