Sera from all symptomatics with
pigeon breeders' lung and many non-symptomatic pigeon breeders react specifically with the pigeon
antigens and in particular pigeon intestinal secretions and isolated pigeon intestinal
mucin and
IgA. In sera from all 82 precipitin-positive pigeon breeders investigated,
IgG1 reacted with both
IgA and
mucin, while
IgG2 reacted predominantly with
mucin only. Sera from all 32 symptomatic patients with
pigeon breeders' lung demonstrated an
IgG3 reaction with
mucin, but only three sera showed reactivity against
IgA and this was very weak. In contrast, only three out of 27 pigeon breeders with pulmonary pathology other than
pigeon breeders' lung and only three out of 23 sera from healthy pigeon breeders showed detectable
IgG3 reactivity with
mucin.
IgG4 from eight sera only reacted with
mucin (n = 7) or
IgA (n = 1) and showed no consistent pattern between subject groups. Precipitin-negative sera from 30 volunteers with no previous pigeon exposure showed no
IgG subclass reactivity with either the pigeon intestinal secretions or the isolated
mucin and
IgA antigens. These results show specific
IgG2 and
IgG3 subclass reactivity to pigeon intestinal
mucin antigen in precipitin-positive sera from pigeon breeders. Further
IgG3 subclass reactivity specific to pigeon
mucin is strongly associated with sera from patients with the active
pigeon breeders' lung disease.