SARS-CoV-2(28) COVID-19(28) COVID-19 patients(16) Tocilizumab(16) Treatment(16) IL-6(16) Patient(16) Cytokine storm(14) severe COVID-19(13) immune(13) occur(12) clinical(12) therapy(12) lead(11) cytokine(11) appear(10) expression(9) immunosenescence(9) Cytokine release syndrome(9) dose(8) individual(8) humoral immune response(8) Immunotherapy(8) vaccination(8) severity(8) characterized(8) disease(8) immune response(7) include(7) HLA-DR(7)