VSIR and viral infectious disease: Interestingly, the frequency of VISTA expression in severe patients was decreased, but it was still higher than that in healthy controls and the convalescent.43 In addition, a study from Canada also found that the SARS-CoV-2–specific T cells (CD154+CD4+, CD137+CD8+ T cells) stimulated by antigens significantly increased VISTA molecules.37 Recent studies of VISTA on T cells, monocytes, and myeloid cells have highlighted its potential significance in driving cytokine storms after viral infection.62