Fig. 1.

Schematic overview of the cohort, the blood sampling, and the applied method for repertoire profiling.A, timeline of blood sampling with annotated relevant treatments, namely monoclonal antibody therapy (tocilizumab), red blood cell transfusion (RBC), red blood cell and plasma transfusions (RBC + Plasma), and red blood cell and platelet transfusions (RBC + Platelets). For each patient (annotated as Pxx), the first blood sample was marked as day 0 (brown circle; T1). The consecutive sampling time points T2 (green circle) and T3 (blue circle) are annotated with the number of days after T1. Several patients are highlighted in color, these individuals are discussed in more detail: blue when receiving tocilizumab monoclonal antibody therapy, orange when the repertoires were analyzed more in depth, and one donor in green for which we measured a completely aberrant serum profile at T3. Patients that did not survive are annotated with a cross. B, schematic overview of the IgG1 and IgA1 profiling methodology. IgA1 and IgG1 are captured from individual’s blood serum and digested in the hinge region by specific enzymes OgpA and IgdE. The released Fab fragments are then separated and analyzed by intact LC-MS, resulting in either an IgA1 or IgG1 clonal profile.