Genetically-driven target tissue over-expression of CD40: A novel mechanism in autoimmune disease

The CD40 gene, an important immune regulatory gene, is also expressed and functional on non-myeloid derived cells, many of which are targets for tissue specific autoimmune diseases, including d thyroid follicular cells in Graves’ disease (GD). Whether target tissue CD40 expression plays a role in autoimmune disease etiology has yet to be determined. Here we show for the first time, that target-tissue over-expression of CD40 plays a key role in the etiology of autoimmunity. Using a murine model of GD, we demonstrated that thyroidal CD40 over-expression augmented the production of thyroid specific antibodies, resulting in more severe experimental autoimmune Graves’ disease (EAGD), whereas deletion of thyroidal CD40 suppressed disease. Using transcriptome and immune-pathway analyses we showed that in both EAGD mouse thyroids and human primary thyrocytes, CD40 mediates this effect by activating downstream cytokines and chemokines, most notably IL-6. To translate these findings into therapy, we blocked IL-6 during EAGD induction in the setting of thyroidal CD40 over-expression, and showed decreased levels of TSHR stimulating antibodies and frequency of disease. We conclude that target tissue over-expression of CD40 plays a key role in the etiology of organ specific autoimmune disease. CD40 in Thyroid Autoimmunity: 1) Incubation of human thyroid cells with G28.5, a CD40 stimulating antibody, and purification of RNA, conversion to cDNA, measurement of mRNA expression using RNAseq. 2) Removal of thyroid tissues from CD40 over-expressing transgenic mice and wild type mice, purification of RNA, conversion to cDNA measurement of mRNA expression using RNAseq.