Initiating pollen sensitization – complex source, complex mechanisms

Table 2 Immunomodulatory activities of various pollen matrix-derived components promoting allergic sensitization

	Plant family	Plant species	Epithelium		DCs					Neutrophil and eosinophil activation/attraction	Increased reactivity in SPT	Enhanced IgE production by B cells	Airway inflammation
	Plant family	Plant species	Barrier permeability	IL-8 secretion	Maturation	CD1d upregulation for interaction with NKT cells	Inhibition of LPS-induced IL-12 secretion	Notch ligands regulation	Inhibition of endosomal cathepsin proteases	Neutrophil and eosinophil activation/attraction	Increased reactivity in SPT	Enhanced IgE production by B cells	Airway inflammation
Tree	Betulaceae	White birch (Betula verrucosa					Adenosine [129]; PPE1 [51, 135, 136]	LMW fraction [95]	PPE1 [120]	PALMs [132,133,134]	PALMs [49]
	Cupressaceae	Japanese cypress (Chamaecyparis obtusa)				Lipids [128]
	Oleaceae	Olive tree (Olea europaea)				Lipids [127]
Grass	Poaceae	Timothy grass (Phleum pratense)	Adenosine [138]	Flavonoid isorham-netin [138]	Gram-positive bacteria [126]	Phospholipids [50]				PALMs [132,133,134]
Grass	Poaceae	Orchard grass (Dactylis glomerata)									Plant virus [123]
Weed	Asteraceae	Short ragweed (Ambrosia artemisiifolia)								Adenosine [116]		PPE1 [137]	Adenosine [116]

LMW low molecular weight, LPS lipopolysaccharide, PALMs pollen-associated lipid mediators, PPE1 phytoprostane E1, SPT skin prick test

ISSN: 2045-7022