IL6 and COVID-19: Likewise, IL-6 is perhaps the most consistently elevated cytokine associated with COVID-19 (7, 10, 13), which was the impetus for early trials testing whether blocking the activity of this cytokine (e.g. with anti-IL-6 receptor antibodies such as tocilizumab and sarilumab) might be useful in treating or preventing severe pneumonia in critically ill COVID-19 patients (43).