But unlike the normal mice, those with altered macrophages showed no signs of inflammation, such as changes in insulin production, high levels of immune chemicals, and macrophages in their belly fat.

They also want to find out whether chemicals in particular types of pollen can be linked to specific immune functions so that the beekeepers can optimize bees' diets.

These range from the idea that clean modern living makes the immune system over-reactive to random allergens to the thought that chemicals in swimming pools are responsible.