Autoantibodies from SLE patients induce programmed cell death in murine fibroblast cells through interaction with TNFR1 receptor

Various pathological processes are known to be associated with the production of IgG autoantibodies, which have high affinity for self-antigens and often cause tissue injury and the development of autoimmune diseases. However, the mechanism of their cytotoxic activity is not clearly understood yet. Here, we have shown that the action of these autoantibodies on cells expressing TNFR1 (the cell surface receptor for TNFα) can cause both caspase-dependent apoptosis and necroptosis of these cells, with suppression of apoptosis resulting in switching to RIP1-dependent necroptosis. Analysis of necroptotic mechanisms has shown that a critical point of necroptosis is phosphorylation of RIP1 and RIP3 kinases, which is followed by the involvement of lysosomes and mitochondria in this process. The induction of cytotoxicity is initiated by the interaction of autoantibodies with TNFR1, and autoantibodies can therefore be regarded as a new functional ligand for this receptor. The innate immunity protein Tag7 (PGLYRP1) described in our recent studies is also a ligand for TNFR1 and competes with autoantibodies for binding with it. Supposedly, the cytotoxic effect of autoantibodies is one of the factors responsible for autoimmune diseases that lead to tissue injury.