From Tim Stevenson
In his look at the wider benefits of vaccines, Michael Brooks describes type 1 and type 2 helper T-cells as competitive, with levels of one going down as the other goes up (17 August, p 38). He then describes a hypothesis that vaccines reduce allergies by boosting type 1 helper T-cells, reducing the number of type 2, which are geared to fight parasitic worms in the gut and are associated with allergies.
This leaves me with a puzzle. Why are tapeworms, which presumably jazz up type 2 helper T-cells, also considered to be effective against some allergies?
Prestwood, Buckinghamshire, UK
