Fel d 1

Fel d 1 is a protein that in cats is encoded by the CH1 (chain 1/Fel d 1-A) and CH2 (chain 2/Fel d 1-B) genes. Fel d 1 is a protein that in cats is encoded by the CH1 (chain 1/Fel d 1-A) and CH2 (chain 2/Fel d 1-B) genes. Fel d 1, produced largely in cat saliva and sebaceous glands, is the primary allergen present on cats and kittens. Fel d 1 is also produced by cat skin itself. The protein is of an unknown function to the animal but causes an IgG or IgE reaction in sensitive humans (either as an allergic or asthmatic response). Removal of soft surfaces in the home (carpet, furniture), frequent washings of bed linens, HEPA filters and even washing cats has been proven to reduce the amounts of Fel d 1 present in the home. Female cats produce a lower level of Fel d 1 than males, and neutered males produce a lower level of Fel d 1 than unneutered males and kittens produce less than adult cats. Neutered males produce Fel d 1 in levels similar to females (both intact and spayed females produce Fel d 1 in similar levels). Even though females and neutered males produce Fel d 1 in lower levels, they still produce enough to cause allergic symptoms in sensitive individuals. Researchers have been investigating reports from cat owners that certain breeds of cats either do not produce Fel d 1 or do so at significantly lower levels than other breeds. For instance, individual Siberian cats from naturally occurring breed native to the Siberian region for which it is named, have been shown to have genetic variants that result in a lower production of Fel d 1. Another breed thought to have a possible genetic disposition not to produce this allergen or to produce less is the Balinese, an offshoot of the Siamese breed. Research continues, hampered by the lack of a reliable genetic test for Fel d 1 production. A variant of Fel-D1 is present in the venom of the slow loris (Primate: Nycticebus). Slow lorises are one of only a few venomous mammals and the only known venomous primate, possessing a dual-composite venom of saliva and brachial gland exudate (BGE). The BGE possesses a protein resembling Fel-D1, which may affect host species as an allergen as a constituent of the venom, and possess a communicative function. The complete quaternary structure of Fel d 1 has been determined. The allergen is a tetrameric glycoprotein consisting of two disulfide-linked heterodimers of chains 1 and 2. Fel d 1 chains 1 and 2 share structural similarity with uteroglobin, a secretoglobin superfamily member; chain 2 is a glycoprotein with N-linked oligosaccharides. Both chains share an all alpha-helical structure.