Antirheumatic drugs, B cell depletion and critical COVID-19: correspondence on 'Clinical course of coronavirus disease 2019 (COVID-19) in a series of 17 patients with systemic lupus erythematosus under long-term treatment with hydroxychloroquine' by Mathian et al. Issue 11 (28th August 2020) - Notz, Quirin; Meybohm, Patrick; Kranke, Peter; Weismann, Dirk; Lotz, Christopher; Schmalzing, Marc