It seems that allergic diseases have reached an almost pandemic level. That’s what a new study states in the journal Nature Medicine. Allergies are caused by a combination of different factors, but that doesn’t help identify the exact culprits.
Some evidence points to the intestines as being the part in our bodies where the root cause might originate. Epidemiological studies have linked commensal bacteria from the colon to the development of allergic diseases. There are typically between 1,000 and 15,000 different kinds of bacterial species in the human gut. Immunologists also point to some immune cells that mediate allergic inflammation.
Commensal bacteria promote allergic inflammation in animal studies, but researchers have yet to find out how exactly this process works. Scientists discovered in this study that treating mice with antibiotics elevated the levels of antibodies known to be important in allergies and asthma (IgE class antibodies). These elevated levels increased the levels of basophils, which are other immune cells playing a role in inflammation.
This also applies to humans, who by default have higher levels of IgE. People with higher levels of IgE are more susceptible to eczema, infections, and asthma.
It has been known that IgE mediates allergies but no one knew that the bacteria living in the gut may use it to check the growth of immune precursor cells in the bone marrow. This in turn may have wide-ranging implications and help explain other chronic inflammatory diseases that have also been associated with changes in these bacterial populations. Commensal bacteria might affect cancer and other autoimmune diseases.
Reference: “Commensal bacteria–derived signals regulate basophil hematopoiesis and allergic inflammation” by David A Hill, Mark C Siracusa, Michael C Abt, Brian S Kim, Dmytro Kobuley, Masato Kubo, Taku Kambayashi, David F LaRosa, Ellen D Renner, Jordan S Orange, Frederic D Bushman and David Artis, 25 March 2012, Nature Medicine.