With asthma and allergy cases amongst young people at an all time high, a study from scientists in Switzerland offers a breath of fresh air. Gabriela Senti and her colleagues at University Hospital Zurich, writing in this week's PNAS, have found that injections designed to desensitise people with allergies can work much more powerfully if they are administered into a lymph node rather than under the skin.
Traditionally doctors have attmempted to damp down overzealous immune responses in people with allergies by injecting weak doses of the offending allergen into the skin. The idea of this therapy is to provoke immune tolerance towards the foreign material by pursuading the immune system to regard it as a friend rather than a foe. Unfortunately this approach has mixed results and can be dangerous because it may trigger severe anapyhlactic reactions. Consequently people with the most severe allergies, who have the most to gain from desensitisation treatments, are often unable to be treated in this way. But this approach is probably flawed because the skin is heavily primed to react to allergen exposure, rather than developing tolerance.
Instead, the Swiss team reasoned, allergens would probably be better off injected into lymph nodes where allergens are normally introduced to the immune system and where immune cells are educated. Working on this premise the researchers recruited 183 hayfever sufferers and randomly assigned them to receive either 54 desensitising injections into the skin over a 3 year period or 3 injections into a lymph node in the groin over a 3 month period. The volunteers were then followed-up for the next 3 years during which allergy symptoms, responses to skin prick tests and anti-allergy medication use were monitored.
The results were very impressive. After three years both groups showed improvements in their allergies but the patients who received the lymph-node injections, which they rated as less painful than skin injections, suffered fewer side-effects and achieved much faster improvement in their symptoms. "The enhanced safety and efficacy observed with intralymphatic therapy...could make immunotherapy more convenient, shorter and less costly," the researchers say.