Felis domesticus minor allergens (Fel d 2–Fel d 8) (Fel d 2–8)

Fel d 2 through Fel d 8 represent the minor allergens found in the domestic cat (Felis domesticus), distinct from the primary major allergen Fel d 1 [WHO/IUIS, allergen.org]. These proteins belong to diverse molecular families, including serum albumins (Fel d 2), cystatins (Fel d 3), lipocalins (Fel d 4 and Fel d 7), and latherins (Fel d 8) [Smith et al., 2011, PMID: 21705013]. While Fel d 1 is responsible for the majority of cat allergies, these minor allergens play significant roles in specific clinical phenotypes, such as the 'pork-cat syndrome' associated with Fel d 2 cross-reactivity with porcine albumin [Hilger et al., 1997, PMID: 9236506]. In clinical practice, these molecules are the targets of diagnostic component-resolved diagnostics and allergen-specific immunotherapy (AIT) [Sastre, 2010, PMID: 20642575]. AIT aims to desensitize the patient's immune system by controlled exposure to these proteins, shifting the immune response from a Th2-mediated allergic profile to a more tolerant state characterized by regulatory T cells and IgG4 production [Akdis & Akdis, 2014, PMID: 25455048]. Understanding the specific sensitization profile to these allergens helps in predicting the success of immunotherapy and the risk of cross-reactions with other animal species.

Other names

Fel d 2Fel d 3Fel d 4Fel d 5Fel d 6Fel d 7Fel d 8Cat serum albuminCat cystatinCat lipocalinCat IgACat IgMCat latherin-like protein

Allergen-specific immunotherapy (AIT) induces immune tolerance by promoting the differentiation of regulatory T (Treg) and B (Breg) cells, which secrete inhibitory cytokines like IL-10 and TGF-beta [Akdis & Akdis, 2014, PMID: 25455048]. This leads to a shift from a Th2 to a Th1 immune response and the production of allergen-specific IgG4 antibodies that compete with IgE for allergen binding, thereby preventing mast cell and basophil degranulation [Sastre, 2010, PMID: 20642575].