Allergies and Me 05: Why Haven't Allergy Genes Been Discovered?

　Allergies are said to result from an overreaction of the immune system (specifically Th2 immunity) that originally evolved to defend against parasitic infections. Here, I explore why specific "allergy genes" have never been identified—despite the long-held belief that allergies are hereditary—by examining the relationship between humans and parasites.

　Unlike viruses or bacteria, which often spread via airborne transmission or droplets, parasites are contracted through food, water, or soil. Humans are mammals; we are nourished by our mothers' milk during infancy and fed by our parents during childhood. Because children live in the same environment and consume the same food as their parents, there is a very high probability that they will be exposed to the same parasites. Consequently, children need to develop immunity against these same parasites. However, if this immunity were determined solely by genetics, it would lack the necessary flexibility to adapt to changing environmental conditions; thus, a purely genetic basis seems unlikely. I believe this explains why no specific allergy genes have been discovered.

　An RSV vaccine was released last year. Administering this vaccine to expectant mothers confers immunity upon the newborn; this can be considered an example of applying the concept of "inheritance without genes" to medical practice in the field of viral infection prevention.

　In my previous blog post, I noted that cases of Japanese cedar pollinosis among children in Kumamoto began to rise around the year 2000; I suspect that this increase may have been driven by children inheriting the condition from their parents.

　Investigating the mechanisms of allergic inheritance could prove useful not only for preventing allergies but also for the development of vaccines to prevent parasitic infections in children.