Infection & autoimmune disease Trigger Cancers: Rarely, a cancer can cause an AI disease. Direct tumor of an immune organ such as the thymus or bone marrow (i.e. athymoma orlymphoma). However, AI disease is very rare from these disorders, so it seems that despite their importance to the immune system, a failure at these sites is not the only problem required for AI disease to result.
The mechanism of paraneoplastic AI is believed to be that the cancer causes a hidden antigen to be shown to the immune system. This antigen is attacked, but by coincidence, this antigen is also at another body site (e.g. the retina), and the immune system mistakenly attacks the retina as an innocent bystander.
The methods whereby a particular trigger might cause the conversion of the immune system into an autoimmune reaction.