Background and aims:
Constitutional factors which predict serological and clinical sensitivity to inhaled antigens resulting in extrinsic allergic alveolitis (EAA) are incompletely understood. In order to identify whether a predisposition to Th1 or Th2-type lymphocyte responses was responsible we measured the surrogate markers for Th1 (PPD sensitivity and serological responses to common respiratory viruses) and for Th2 (total IgE) in 100 pigeon breeders. These were compared with the IgG antibody titre to inhaled avian antigens and clinical evidence of EAA.

Results:
There was a highly significant association between serum IgG antibody to avian antigens and symptoms associated with EAA. Skin and in vitro lymphocyte sensitivity against PPD from M. avium and M. tuberculosis was significantly inversely associated with the antibody response to avian antigen (p=0.04) and EAA (p<0.01, Fishers exact test). In contrast the antibody titres to influenza A and B, and adenovirus were each positively associated with the antibody titre to avian antigen (p<0.05 for each) but not EAA. There was no significant association between total IgE and avian-antigen specific IgG or EAA.

Conclusion:
EAA does not appear to be associated with either a classical Th1-type phenotype as assessed by tuberculin sensitivity, nor a classical Th2-type phenotyope as assessed by total IgE. Serum IgG antibody to avian antigens were positively associated with Th1-type anti-viral responses but negatively associated with Th1-type tuberculin sensitivity. These observations suggest that EAA can occur in an individual irrespective of their Th1 or Th2-type phenotypes.

Eur Respir J 2002;20:314S