Permeability or local production of immunoglobulins and other inflammatory proteins in asthma

Immunoglobulins in the epithelial lining fluid of the respiratory tract either originate from the systemic circulation or they are locally produced by plasma-cells in the mucosa. For polymeric immunoglobulins (dimer IgA and IgM) specific receptors on the surface of epithelial cells allow facilitated transport of these immunoglobulins into the lining fluid. Local inflammatory reactions in the lung will damage the respiratory membrane, which results in an increased leakage of proteins into the lining fluid. This increased leakage complicates the differentiation between local production of immunoglobulins and passive permeation. In asthma patients inflammation of the respiratory epithelium is found. This inflammation may be the result of non-immunologically triggered processes as well as of immunological reactions. In the experimental part of this paper we analyse possible local production of immunoglobulins and other proteins within the lungs of patients with asthma. This is performed with the use of steady-state protein concentrations in serum and bronchoalveolar lavage fluid. Information on the permeability of the respiratory membrane can be obtained by the measurement of proteins that are not produced within the lungs. Information on local production can be obtained by comparing the epithelial lining fluid to serum concentration ratios of proteins with identical molecular masses.