Pollen allergen Phl p 2 (Phl p 2)

Pollen allergen Phl p 2 is a major protein allergen derived from the pollen of Timothy grass (Phleum pratense), which is a primary cause of seasonal allergic rhinitis and asthma globally. It belongs to the group 2/3 grass pollen allergen family and possesses a characteristic nine-stranded beta-sandwich structure that resembles an immunoglobulin fold. Biologically, Phl p 2 is classified as an expansin-like protein, potentially involved in plant cell wall loosening during pollen tube growth. In the context of human disease, Phl p 2 acts as a potent antigen that triggers Type I hypersensitivity by cross-linking IgE antibodies on mast cells and basophils, leading to the release of inflammatory mediators. It is a critical component in allergen-specific immunotherapy (AIT), where it serves as the active agent to induce immunological tolerance in sensitized patients. Therapeutic products, such as standardized grass pollen extracts (e.g., Grazax, Itulatek), utilize Phl p 2 to shift the immune system from a Th2-mediated allergic response to a Th1 and regulatory T-cell (Treg) mediated response. This shift is monitored through biomarkers such as increased levels of allergen-specific IgG4 antibodies, which act to block IgE-mediated activation. Safety concerns associated with Phl p 2-based therapies include the risk of systemic allergic reactions and anaphylaxis, necessitating careful dose escalation.

Other names

Group 2 grass allergenPHLPII proteinTimothy grass allergen Phl p 2Phl p II

Allergen-specific immunotherapy (AIT) involving the induction of immune tolerance, shifting the immune response from Th2 to Th1/Treg, and the production of allergen-specific blocking IgG4 antibodies.