I've mentioned this many times on this forum but keep getting ignored or ridiculed. The link between mast cells/immune system and hairloss is undeniable. I would bet any amount of money that an immune system dysfunction, which triggers an influx of mast cells (and therefore creates inflammation) creates a chain reaction of overproduction of PGD2 which both inhibits hair growth and causes it to miniaturize. PGD2 is only a component since removing PGD2 does not necessarily cause hair to grow back, but to me the link between hairloss and the immune system is pretty obvious.
- Mast Cells are the predominant source of PGD2.
- Mast Cells are known to develop in the microenvironment of Hair Follicles.
- PGD2 is known to inhibit hair growth
References:
"[Mast Cells] are functionally important modulators of hair follicle cycling, specifically during anagen development." -
https://www.ncbi.nlm.nih.gov/pubmed/8528600
"These data support the notion that Mast Cells function as hair cycle regulators and are involved in the control of HF regression." -
https://www.ncbi.nlm.nih.gov/pubmed/9354767
"We found significantly more dermal mast cells immunoreactive for prostaglandin D-synthase in the vertex compared to the lateral aspects of the scalp, with a decrement that spatially approximated the pattern of androgenetic alopecia. This difference was present in both balding and non-balding scalps and was independent of gender. Dual labeling established dermal cells expressing prostaglandin D-synthase as mast cells." -
https://www.ncbi.nlm.nih.gov/pubmed/24438498
"infiltrating lymphocytes and mast cells have been identified around the miniaturizing follicle (9), especially in the area of the stem cell–rich bulge area" -
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3319975/
"We also noted a unique peak of PGD2 production within hours of depilation, which was not seen in the spontaneous hair cycle in Fig. 3B. This coincides with degranulation of mast cells observed previously after depilation" -
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3319975/
"Prostaglandin D2 (PGD2) is the predominant prostaglandin product released by mast cells. It is found prevalently in the central nervous system and peripheral tissues, where it performs both inflammatory and normal processes." -
http://www.mastattack.org/2015/04/mast-cell-mediators-prostaglandin-d2-pgd2/
"Prostaglandin D2 (or PGD2) is a prostaglandin that binds to the receptor PTGDR (DP1), as well as CRTH2 (DP2).[1][2] It is a major prostaglandin produced by mast cells – recruits Th2 cells, eosinophils, and basophils. In mammalian organs, large amounts of PGD2 are found only in the brain and in mast cells." -
https://en.wikipedia.org/wiki/Prostaglandin_D2
"TNF was thought to be produced primarily by macrophages,[33] but it is produced also by a broad variety of cell types including lymphoid cells, mast cells, endothelial cells, cardiac myocytes, adipose tissue, fibroblasts, and neurons.[3] Large amounts of TNF are released in response to lipopolysaccharide, other bacterial products, and Interleukin-1 (IL-1). In the skin, mast cells appear to be the predominant source of pre-formed TNF, which can be released upon inflammatory stimulus (e.g., LPS).[34]" -
https://en.wikipedia.org/wiki/Tumor_necrosis_factor_alpha
"Hair Follicles provide a unique microenvironment for local development of mast cells" -
https://www.ncbi.nlm.nih.gov/pubmed/12738661
"[Mast Cells] are functionally important modulators of hair follicle cycling, specifically during anagen development." -
https://www.ncbi.nlm.nih.gov/pubmed/8528600
"During normal follicle cycling in mice, Ptgds and PGD2 levels increase immediately preceding the regression phase, suggesting an inhibitory effect on hair growth. We show that PGD2 inhibits hair growth in explanted human hair follicles and when applied topically to mice." -
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3319975/
"Our studies show that prostaglandins are dysregulated in Androgenetic Alopecia, the most common type of hair loss in men. Specifically, PGD2 inhibits hair growth and thus represents a negative counterbalance to the positive effects on hair growth shown for PGE2 and PGF2α" -
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3319975/