Notably, the dynamic expression pattern of VSIR (VISTA) observed in COVID-19 patients, as reported by Rendeiro et al. (Tan and Li 2022), suggests stage-dependent immunoregulatory roles—upregulated in CD4+ and CD8+ T cells during mild/moderate disease to prevent hyperactivation, but reduced in severe cases while remaining above baseline, reflecting a compensatory mechanism following T-cell exhaustion. Here, CD4 is linked to COVID-19.