C3 and prion disease: Moreover, the identified genes whose expression was affected by stimulation according to the concentration of PM in the air of Krakow are involved in specific intracellular pathways, including regulation of extracellular matrix by Interleukin-1 (e.g., C3 and CCL7) and transcripts related to prion diseases (e.g., EGR1 and NOTCH1).