Group 5 allergen (Dactylis glomerata) (Dac g 5)

Dac g 5 is a major protein allergen found in the pollen of Dactylis glomerata, commonly known as Orchard grass or Cocksfoot grass (UniProt: Q93WP9). It belongs to the group 5 grass pollen allergen family, which is recognized as one of the most potent triggers of IgE-mediated Type I hypersensitivity in individuals with hay fever or allergic asthma (Allergen.org). Biologically, group 5 allergens are thought to play a role in pollen tube growth and development within the plant, although their exact physiological function is still being elucidated. In humans, exposure to Dac g 5 via inhalation leads to the cross-linking of allergen-specific IgE on the surface of mast cells and basophils, triggering the release of inflammatory mediators like histamine that cause allergic symptoms. As a therapeutic target, Dac g 5 is the primary component used in allergen-specific immunotherapy (AIT) to desensitize patients and induce long-term immune tolerance. AIT products, such as the five-grass pollen sublingual tablet (Oralair) or standardized subcutaneous extracts, work by gradually exposing the immune system to the allergen to shift the response from a pro-allergic Th2 profile to a regulatory or Th1-mediated profile. This process is typically monitored through biomarkers such as increased allergen-specific IgG4 blocking antibodies and reduced skin prick test reactivity.

Other names

Major allergen Dac g 5Cocksfoot grass pollen allergenOrchard grass pollen allergenDac g V

Allergen-specific immunotherapy (AIT) induces immune tolerance by shifting the T-cell response from Th2 to Th1, promoting regulatory T-cell (Treg) activity, and increasing the production of allergen-specific IgG4 blocking antibodies.