IgM in the airways of asthma patients.

In order to obtain information on the role of IgM in the pathogenesis of asthma, we assayed IgM in the broncho-alveolar lavage fluid (BALF) from 14 non-smoking patients with asthma and 9 non-smoking healthy persons, using an ELISA. The concentrations of IgM in the epithelial lining fluid (ELF) were calculated on the basis of urea in serum and BALF. The concentrations of IgM in ELF after correction for serum IgM, cQIgM, from the patients as a group were higher than those from controls (Mann-Whitney U test, p less than 0.05). The IgM in BALF and serum, analysed by sucrose density gradient centrifugation was pentameric. The transudation of IgM from blood into ELF was compared with that of alpha 2 macroglobulin (A2M), a protein with a similar molecular mass. In 6 patients the cQIgM/cQA2M value was above the upper value of the range for controls suggesting abnormal local production of IgM. The presence of the secretory component (SC) linked to IgM was determined by ELISA. The percentage of SC-IgM in BALF was increased in 5 out of 7 patients tested. The increased local IgM concentrations and its increased local production may suggest a role for local IgM-mediated reactions in the inflammatory events associated with asthma.