Among the top interactions in severe COVID-19 samples were several interactions between MHC class I molecules and killer Ig-like receptors (KIRs); interactions between the inhibitory receptors LILRB1, Tim-3 (HAVCR2), and Lag-3 and their cognate ligands; and interactions involving chemokine receptors and integrins (Fig. 2A). Here, LILRB1 is linked to COVID-19.