The role of pan-allergens
An interesting subgroup of grass pollen allergic patients are sensitized
to profilin, a pan-allergen present in all vegetable tissues, with a
highly conserved structure. Usually, profilin is a confounding
diagnostic factor, which is minimized by CRD diagnosis either “in
vitro” or even “in vivo”39. Profilin
sensitization strongly associates with grass pollen allergy35 in base to a
relatively high profilin content in grass pollen compared to other
pollens 40. Usually,
sensitized profilin patients present no food-mediated reaction or only
local (oral) ones. However, in areas of very high grass pollen exposure,
some allergic patients do not respond to AIT and present severe food
profilin-mediated reactions41,42.
In fact, T cell reactivity to profilin increases along with grass pollen
intensity exposure. Moreover, in patients from central Spain, T cell
proliferation induced by profilin is similar to that induced by the
major allergen Phl p 134. These peculiar
patients, as well as others exposed to very high pollen levels, can be
identified by combining CRD with clinical evaluation and provide
invaluable models to understand allergic inflammation and AIT mechanisms
and its limitations.
Finally, patients sensitized simultaneously to the pollen pan-allergens
polcalcin and profilin have been shown to have twice as many primary
sensitizations and to duplicate as well allergy disease evolution time36, suggesting that AIT
might not be effective. Similar results supporting clinical value for
Phl p 7 and Phl p 12 have been described in pediatric cohorts37.Moreover, this
specific double sensitization profile to pan-allergens is not linked to
any particular pollen36. At this moment
other grass allergens present a limited diagnostic value for AIT
decisions and some of them provide confounding information due to lack
of specificity 43.
Figure 1 represents an algorithm to support decision-making in the
selection of AIT for grass pollen allergy.