Can we reverse peanut allergies?
The human immune system confers on us a remarkable ability to resist a virtually infinite number of pathogens. Our bodies come into contact with a tremendous variety of microorganisms on a daily basis, and for the vast majority of them, we do not even notice that we have come into contact with them. Our immune system allows us to resist them without any adverse symptoms at all. For the occasional microbe that causes us to consciously register their presence, disease is the result. The immune system is typically able to eliminate them as well, after a period of illness and recovery.
Allergies are the result of an immune dysfunction; the immune system perceives something as a threat and initiates a response to curtail that foreign material, when in fact no response is necessary. Allergic responses can range from moderate to life-threatening, and individuals with defined allergies can only deal with them by not coming into contact with the items that trigger them. There is significant epidemiological evidence that many childhood allergies are increasing in frequency, and allergies to peanuts are among the most common. Furthermore, peanut allergies are one of the most common fatal or near-fatal childhood food allergies.
This article in the Journal of Immunology, and found via the science blog io9.com, describes a therapeutic approach for potentially reversing a peanut allergy. Researchers at Northwestern University in Chicago utilized mice that had been challenged with peanut proteins to induce an allergic response. They then removed white blood cells from those mice, and bound additional peanut proteins to the surfaces of the white blood cells, and injected those modified blood cells into the mice. The modified blood cells induced a process called tolerization in the mice, where the mouse’s immune system becomes tolerant to the peanut proteins. Senior author of the study Paul Bryce says:
We think we’ve found a way to safely and rapidly turn off the allergic response to food allergies. T cells come in different ‘flavors.’ This method turns off the dangerous Th2 T cell that causes the allergy and expands the good, calming regulatory T cells. We are supposed to be able to eat peanuts. We’ve restored this tolerance to the immune system.
The system appears to be very effective in the mouse model, and mice were able to be fed peanuts without adverse reactions after just two treatments with the modified white blood cells. This is an impressive result, and holds significant promise for being able to treat these allergies in humans. However, there are issues with translating this to a treatment for patients. Laboratory mice are highly inbred, and human populations are not. The inbred nature of lab mice is an advantage for medical research, as it maximizes the reproducibility of experiments, however this leads to a source of significant variability when applied to people.
Avoidance is the approach that is typically used with allergy patients, however there is growing evidence that tolerization may be a useful therapy to allow patients to gradually become used to the presence of triggering foods. Patient to patient variability limits the success of this approach, plus it may be difficult to determine exactly what the trigger is in each case. In the case of this therapeutic approach, this latter point is particularly important, as success depends upon linking a purified set of triggering proteins to the patient’s white blood cells in the laboratory. The complex mixture of compounds within a given food would not lend itself easily to doing this. Still, the approach may allow patients to enjoy foods that they now stay far away from. Bring on the grilled chicken in spicy Thai peanut sauce!