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Twenty-one symptomatic subjects with pigeon breeders' lung (PBL) and 10 asymptomatic pigeon breeders, with a similar exposure to pigeon antigens, underwent bronchoalveolar lavage. Total IgG, IgM and IgA in lavage fluid were determined as were specific antibody levels against antigens in pigeon serum and droppings. Results were converted to levels in epithelial lining fluid (ELF) using lavage and serum urea ratios. It was found that symptomatics represent a group that is hyperreactive to pigeon antigens compared with the asymptomatic group with significantly higher IgG, IgM, IgA levels as well as specific antibody levels against pigeon serum and droppings. Paired serum and ELF samples from 12 symptomatic subjects showed significantly elevated IgG, IgM and IgA levels in ELF compared with serum when values were expressed in terms of albumin. This strongly supports the concept of local production of immunoglobulins within the lung after inhaling immunogens as opposed to their diffusion from the vasculature. Results for IgA indicate that any putative protective role for this immunoglobulin is not valid in relation to the prevention of extrinsic allergic alveolitis. Analysis of smoking habits, lung immunoglobulins and response to inhalation challenge confirm the negative influence of smoking on total and functional lung immunoglobulins; however, levels in the ELF of ex-smokers suggest that the effect of smoking is not permanent. Smoking did not prevent responses to inhalation challenge.

Bronchoalveolar lavage fluid (BALF) from subjects with a variety of interstitial lung diseases (active sarcoidosis, pigeon breeders' disease (PBD), asymptomatic pigeon breeders, patients with idiopathic pulmonary fibrosis) and from control subjects were assayed for interleukin-6 (IL-6) using a novel radioimmunoassay system. IL-6 was detectable in BALF from all groups, with disease groups showing significantly increased IL-6 levels compared with controls (P less than 0.01 in all cases). When these results were standardized, using urea to compensate for dilution effects in the BALF, only the asymptomatic pigeon breeders had significantly higher IL-6 levels than the controls (P less than 0.025), with all other groups showing no difference. When albumin was used for standardization, both the PBD group (P less than 0.001) and the sarcoidosis patients (P less than 0.01) had considerably lower levels of IL-6 than the control subjects. Using either albumin or urea for standardization, the PBD patients had significantly lower levels of IL-6 than do their asymptomatic counterparts (P less than 0.001 in both cases). This is contrasted by the finding of greatly elevated levels of IgG in the BALF of the PBD patients compared with asymptomatics (P less than 0.001). There was, however, no relation between IL-6 and IgG in any patient group, although the PBD patients had the lowest IL-6 and highest IgG as a group. These findings may suggest a mechanism by which asymptomatic subjects remain free from clinical complaints.