Hypothetical model of inflammatory reactions in sarcoidosis, comparing the immune response in the lungs of patients with Löfgren's syndrome and those without. The triggering event is the presentation of an (unknown) antigen by antigen-presenting cells (APC) to T cells. In the lungs of patients, there are fewer regulatory T cells, as well as a lower CD4+ T cell expression of TIM-3, compared to healthy controls. Both these factors may contribute to the characteristic Th1-type inflammation. Differences in the exact type of antigen(s) presented in the respective patient subgroups, as well as antigen clearance or persistence, may contribute to the enhanced Th1 response seen in non-Löfgren's patients, which is associated with a lower CD4+ T cell TIM-1 expression compared to Löfgren's patients. Markers indicated in bold are those included in the present study, for the others see [22, 31] and .