Albumin, transferrin and alpha2-macroglobulin in bronchoalveolar lavage fluid following exposure to organic dust in healthy subjects.

Abstract

The purpose of the present study was to investigate leakage of plasma proteins in connection with the inflammatory airway reaction following exposure to dust in a pig house. Inhalation of swine-house dust causes intense inflammation with influx of inflammatory cells, predominantly neutrophils, into the airways. The aim of the study was to compare the concentration of three different proteins in bronchoalveolar lavage (BAL) fluid as markers for the inflammation. In twenty healthy, non-allergic, non-smokers, not previously exposed to farm dust, BAL was performed approximately 2 weeks before and 24 h after 3 h of exposure to swine dust in a swine-confinement building. Differential cell count and protein concentration were assessed in BAL fluid. Albumin (66.5 kDa) and alpha2-macroglobulin (720 kDa) were quantified by the use of enzyme-linked immunosorbent assay (ELISA) techniques, and transferrin (80 kDa) by zone immunoelectrophoresis assay. The coefficient of variation for repeated protein measurements was <9%. alpha2-Macroglobulin concentration increased six-fold, from 68.0 (36.1-99.9) microg/l, mean (95% CI) before exposure to 411.2 (254.0-568.4) microg/l after exposure (P < 0.001). Transferrin and albumin increased from 19.7 (16.2-23.1) mg/l and 1.8 (1.4-2.2) mg/l, 2.6 and 1.9 times, respectively (P < 0.001). There was significant correlation between the exposure-induced increased protein levels in BAL fluid, although alpha2-macroglobulin was a better discriminator of pre- and post-exposure concentrations than were albumin and transferrin. There was a significant correlation between the exposure-induced BAL-fluid neutrophilia and the increase in alpha2-macroglobulin and transferrin, but not for albumin. This correlation was found only when pre- and post- differences, but not ratios, of plasma proteins were compared. The levels of plasma proteins increased in BAL fluid following exposure to swine-house dust. alpha2-Macroglobulin was a better marker of this plasma leakage than were albumin and transferrin.