Figure 7. Model for the role of PAFR agonists during immune suppression induced by UV radiation.

Skin damage induced by UV irradiation leads to secretion of PAF by keratinocytes and oxidation of phopsholipids that bind to the PAFR on mast cells. This induces the surface expression of CXCR4. UV irradiation of the skin also leads to the up-regulation of CXCL12 by LN cells [14]. This facilitates the migration of CXCR4-positive mast cells from the dermis to the draining LNs. We propose that IL-10-secreting mast cells [9] migrate to the skin draining LNs and mediate immune suppression.