Phleum pratense allergen 4 (Phl p 4)

Phleum pratense allergen 4 (Phl p 4) is a major glycoprotein allergen found in the pollen of Timothy grass, which is a primary cause of seasonal respiratory allergies worldwide. It belongs to the berberine bridge enzyme (BBE)-like protein family and biologically functions as a glucose dehydrogenase, utilizing a bicovalently bound flavin adenine dinucleotide (FAD) cofactor [2, 10]. Phl p 4 is recognized by IgE antibodies in approximately 75-82% of grass-pollen-allergic individuals, making it a critical component for component-resolved diagnosis (CRD) of seasonal allergies [4, 6]. Sensitization to Phl p 4 often occurs early in childhood and can serve as a predictor for the development of allergic rhinitis and asthma [5, 14]. In clinical practice, Phl p 4 is a key constituent of allergen-specific immunotherapy (SIT) formulations, such as Timothy grass pollen extracts, which aim to induce immunological tolerance and shift the immune response from a Th2-mediated allergic state to a protective Treg/Th1-mediated state [13, 15]. A notable feature of Phl p 4 is the presence of cross-reactive carbohydrate determinants (CCDs), which can lead to diagnostic challenges due to broad cross-reactivity with other plant and insect allergens [4, 10].

Other names

Phl p 4Phl p IVGroup 4 grass pollen allergenTimothy grass pollen allergen 4

Allergen-specific immunotherapy (SIT) involving the induction of allergen-specific IgG4 antibodies and the modulation of T-cell responses (Th2 to Th1/Treg shift) to promote immune tolerance [13, 15].