We also performed interactomic analysis in human plasma, using C3-LHF1 and C3 as purified by a C3-specific nanobody (hC3Nb2, Pedersen et al, 2020b) as a control (n = 4 individual plasma samples for healthy controls and SLE patients, Appendix Fig. S3A, Dataset EV17). Here, C3 is linked to systemic lupus erythematosus.