Frontiers Mast Cell Activation in Brain Injury, Stress, and Post traumatic Stress Disorder and Alzheimer's Disease Pathogenesis Detecting Changes in Mast Cell Numbers Versus Activation in Human Disease: A Roadblock for Current Biomarkers? ScienceDirect Frontiers Glutathione deficiency in the pathogenesis of SARS CoV 2 infection and its effects upon the host immune response in severe COVID 19 disease Mast cells are hypersensitive immune cells that release histamine and other inflammatory mediatorsoften in response to oxidative stress, environmental toxins, and immune imbalance. Many patients with MCAS have low levels of glutathione.