TNFSF13B and COVID-19: Given a significant role of the adaptive immune system in the clinical course of COVID-19 and in the outcome of the vaccination program in patients with reduced kidney function, we analyzed selected factors that are involved in B cell function; B cell activating factors (BAFF), Interleukin (IL-4), Interferon (IFN)-α and T cell function: soluble Programmed death-ligand (sPD-L)-1, soluble Cluster of differentiation (sCD)-25, sCD40L, sCD95, and their relation to in-hospital and 30-day mortality in hospitalized patients with COVID-19.