Profilin (PFN)

Profilins are a family of small (12–15 kDa), ubiquitous actin-binding proteins that play a fundamental role in regulating the eukaryotic cytoskeleton by promoting actin polymerization and interacting with various signaling molecules like phosphoinositides (UniProt, 2024). In the context of clinical immunology, they are recognized as "panallergens" because their highly conserved structure across diverse plant species—including trees, grasses, weeds, and food crops—leads to widespread IgE cross-reactivity (PubMed, 2015). This cross-reactivity is the primary mechanism behind Pollen-Food Allergy Syndrome (PFAS), where patients sensitized to pollen profilins experience allergic reactions upon consuming botanically unrelated fruits or vegetables (PubMed, 2020). While profilins are typically heat-labile and susceptible to proteolytic digestion, often limiting symptoms to the oral mucosa, they can occasionally cause systemic reactions in sensitized individuals. Therapeutic interventions include the use of anti-IgE monoclonal antibodies like Omalizumab, which prevents the binding of cross-reactive IgE to mast cells, and allergen-specific immunotherapy (AIT) designed to induce immunological tolerance (NIH, 2023). Diagnostic approaches increasingly rely on component-resolved diagnostics (CRD) to distinguish between primary sensitization and cross-reactivity mediated by these proteins.

Other names

Panallergen profilinActin-binding proteinBet v 2Phl p 12Hev b 8Mal d 4Ara h 5Fra a 4Pyr c 4Cuc m 2Panallergen profilins binding cross-reactive IgE

Omalizumab binds to the Cε3 domain of free IgE, preventing its interaction with the high-affinity IgE receptor (FcεRI) on mast cells and basophils, thereby inhibiting the allergic cascade triggered by profilin cross-linking (NIH, 2023). Allergen-specific immunotherapy (AIT) involves the administration of increasing doses of the allergen to induce regulatory T cells and IgG4 blocking antibodies, leading to long-term immunological tolerance and desensitization (PubMed, 2021).