# Pollen-Food Allergy Syndrome: Allergens, Clinical Insights, Diagnostic and Therapeutic Challenges
## 6 Protein Families Involved in PFAS  
As mentioned before, PFAS is a result of immunological cross-reactivity between airborne pollen allergens and structurally similar proteins present in various plant-based foods. These shared allergens, referred to as panallergens, are proteins with highly conserved structures found across diverse plant species. Their stability and ubiquitous presence make them central to the pathophysiology of PFAS, as they form the molecular link between pollinosis (pollen allergy) and food allergy [33]. Understanding these panallergens provides critical insight into the mechanisms of PFAS and informs diagnostic and therapeutic approaches. In 2004, [PERSON] et al. proposed a systematic classification of allergens into families based on their structural and functional properties [116]. Among the many allergenic protein families, six have been identified as significant contributors to PFAS due to their ability to induce IgE cross-reactivity between pollens and foods. Of these, three families are particularly well-characterized: PR-10 proteins, profilins, and LTPs [44]. These proteins are involved in essential biological processes in plants, such as defense against pathogens and environmental stress, but in humans, they act as allergens that trigger hypersensitivity reactions. Three additional families--thaumatin-like proteins (TLPs), \(\beta\)-1,3-glucanases, and isoflavure reductases (IFRs)--have also been implicated in PFAS, though they are less well understood [44; 117]. Emerging research highlights other promising candidates, such as gibberellin-regulated proteins (GRPs), which are beginning to be recognized as cross-reactive allergens [118]. Figure 2 illustrates the relative stability and potential for severe systemic allergic reactions of various allergenic protein families, ranging from highly heat- and digestion-sensitive proteins such as PR-10 and profilins, to highly stable proteins like LTPs. The gradient highlights the continuum of allergenic risk, with more stable proteins generally associated with a higher likelihood of systemic reactions, including anaphylaxis [119]. This visualization underscores the varying allergenic profiles of these protein families, which play a critical role in the diagnosis and management of IgE-mediated allergic conditions [44; 98]. Figure 2: Stability and potential for severe systemic reactions of allergenic proteins [33; 44; 119; 120]. The chart illustrates the relative stability (resistance to heat and digestion) and associated risk of severe systemic allergic reactions among different allergenic protein families. Proteins such as PR-10 and profilins are shown with lower stability and reduced potential for systemic reactions, while LTPs exhibit high stability and significant potential for systemic allergic responses. The arrow gradient represents the continuum from low to high stability and systemic reaction potential. GRPs: Gibberellin-Regulated Proteins; IFRs: Isoflavonoid reductases; LTPs: Lipid Transfer Proteins; PR-10: pathogenesis-related protein group 10; TLPs: Thaumatin-like proteins. Table 1 and Figure 3 provide a list of major allergen sources, their specific allerggenic proteins, and distribution worldwide. This table has been compiled using information from the Allergen Nomenclature Database (WHO/IUIS), which provides standardized data on allergen sources, protein families, and nomenclature, as well as from the Global Biodiversity Information Facility (GBIF), an authoritative resource on species distribution and biodiversity [121; 122].