PPT1 and Autoimmunity: Recent findings indicate that palmitoyl-protein thioesterase 1 (PPT1) influences TLR9 function by removing its S-palmitoylation in lysosomes, affecting TLR9 trafficking and autoimmunity in SLE.333 Biochemical assays and mass spectrometry have shown that TLR9 is S-palmitoylated at cysteine residues C258 and C265.