IFNG and silicosis: The explanation of these findings is still missing because the experimentally induced silicosis gave conflicting results on interferon gamma (IFNγ), the best characterized activator of neopterin (91), with some studies showing an increased level of IFNγ (92) and others finding only the up regulation of IFNs type I with apparently no major impact on the evolution of silicosis (93) or even a dysfunctional signal of IFNγ in macrophages loaded with SiO2 (94).