Inflammation is a complicated immune process that involves numerous components depending on the tissue and trigger [
198]. The specific role of cytokines in inflammation of the brain is still poorly understood as these ‘danger signals’ [
45] are now divided into three different groups: (a) inflammatory cytokines, (b) alarmins, and (c) stressorins, with distinct patterns of secretion and biological properties [
199]. Innate immunity of the brain involves primarily microglia [
200], which communicate with mast cells [
201,
202].
Mast cell-derived mediators, such as histamine and tryptase, can activate microglia [203] leading to secretion of pro-inflammatory mediators including interleukins IL-1β, IL-6, and TNF, known to be increased in the brain of children with ASD [
204]. Mast cells are found in the brain [
205], especially the hypothalamus, thalamus, and third ventricle [
206,
207]. Mast cells are also found in the pineal, the pituitary, and the thyroid glands [
3].