Immunotherapy is effective in patients with severe summer hay fever, but immediate anaphylactic reactions limit its use to specialised centres. Patient selection is extremely important, and chronic perennial asthma should be specifically excluded. As serious reactions occur within minutes a two hour wait for all patients after each injection seems unnecessary.

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Six strains of Mycobacterium tuberculosis of different virulence in guinea-pigs were compared with regard to their resistance to low pH, to hydrogen peroxide (H202) at different pH values and to superoxide (-O,-). Low virulence was associated with susceptibility to H202 in native and isoniazid-resistant strains but not in laboratory-attenuated strain ~3 7~a . H,Oz resistance was only partly related to catalase content. Low virulence was not associated with susceptibility to an acid environment but the tuberculocidal effect of H202 was significantly increased at low pH. The strains were uniformly resistant to -02-and contained similar amounts of superoxide dismutase. The implications of these observations are discussed in the context of mechanisms of host defence in tuberculosis.

No abstract