We next examined the identity of these infiltrated cells, and immunohistochemistry showed strong CD68+ macrophages were seen in the tubulointerstitium of these six autopsies, while moderate numbers of CD8+ T cells were observed in the tubulointerstitium of two cases, whereas low number of CD56+ natural killer (NK) cells were found in the examined COVID-19 post-mortem tissues (Fig. 5a). Here, CD68 is linked to COVID-19.