Fig. 2

Role of stress in induction of Alopecia Areata through the collapse of immune privilege. A CRF released by stress leads to degranulation of mast cells which releases substance P. this substance contributes to the collapse of immune privilege by elevating MHC-I and β2 micro-globulin. Besides, it activates mast cells to release TNF which stops hair growth. It results in premature catagen transition by upregulation of NGF and p75NTR. B CRF increases CD 8 + cells and NKs which increases INF-γ and followed by the increase in MHC-I thus collapse of immune privilege and finally AA