The effect of the autoimmunity-associated gene, PTPN22, on a BXSB-derived model of lupus

- PTPN22 is associated with increased risk to multiple autoimmune diseases including systemic lupus erythematosus.
- Crossing of PTPN22 KO to the BXSB model of lupus allowed us to study the effect on disease.
- PTPN22 KO does not affect disease onset or severity on the male BXSB;B6-Yaa background.
- PTPN22 KO increases autoantibody production in female BXSB;B6 mice but does not accelerate disease.

A single nucleotide polymorphism in PTPN22 is linked to increased disease susceptibility in a range of autoimmune diseases including systemic lupus erythematosus (SLE). PTPN22 encodes the Lyp phosphatase that dampens TCR signaling and is necessary for signaling downstream of toll-like receptors in myeloid cells. To understand these dual functions in disease, we examined the impact of deficiency in PTPN22 on a spontaneous murine model of SLE. Male PTPN22 KO mice carrying BXSB chromosome 1 and the Yaa disease accelerating factor developed disease at a similar rate and severity as PTPN22 WT. In contrast, although female mice showed no differences in survival in the absence of PTPN22, autoantibody production was significantly increased and splenic populations associated with pathogenesis in this model were expanded in the PTPN22 KO group. These findings support the notion that when coupled with other predisposing autoimmunity genes, PTPN22 deficiency contributes to a predisposition to lupus pathogenesis.