GRN and autoimmune disease: However, since Tang et al. [14] showed that PGRN is a high-affinity ligand of the tumour necrosis factor α (TNF-α) receptors 1 and 2 (TNFR1 and TNFR2) and that its anti-inflammatory effect is caused by direct inhibition of these receptors, PGRN has increasingly become the focus of research on autoimmune diseases.