ETIOLOGy 1. Infectious agents: Epstein-Barr virus mycop lasma, macobacteria, retroviruses T lymphocyte and macrophage activation B lymphocyte activation Change of the gene expression Molecular mimicryETIOLOGY 1. Infectious agents: Epstein-Barr virus, mycoplasma, macobacteria, retroviruses – T lymphocyte and macrophage activation – B lymphocyte activation – Change of the gene expression – Molecular mimicry