The effect of negative air ionization on the thymus glands of laboratory rats

Continuous negative air ionization, over two generations, was found to result in depletion of thymus mass when compared with control values. Evidence from adrenal weights suggested that this effect was not mediated via stress effect; it is suggested that there may be a direct action of negative ions on the immune system. The normal pattern of thymic growth and involution was unaffected by such treatment. However, successive generations of animals, raised in a negatively ionized atmosphere, showed no such depletion of thymus mass.