Pulmonary inflammation in parasitic infection: immunoglobulins in bronchoalveolar washings of rats infected with Nippostrongylus brasiliensis

Despite marked pulmonary pathology caused by larval stages of many helminth parasites, little is known about the mechanisms of immune and inflammatory responses to parasites in the respiratory tract. Using bronchoalveolar lavage (BAL) we have retrieved soluble proteins and cells from the respiratory tract of rats given a primary or secondary infection with the nematode Nippostrongylus brasiliensis. Total amounts of different immunoglobulin classes and albumin in BAL fluids and serum were quantitated using an ELISA. Analysis of the cellular component showed an increase in alveolar macrophages, neutrophils, eosinophils and lymphocytes on different days post-infection similar to our earlier findings. A time course study revealed that the concentrations of total protein, albumin, IgG, IgA and IgM in BAL fluids of infected animals were increased from days 2 to 32 after a primary infection. The magnitude of this increase was higher following a challenge infection (secondary) with the same parasite. Moreover, there was also a biphasic increase in total protein, IgG and IgA after secondary infections, with peaks on days 2 to 4 and 11 to 21 post-infection. A comparison of immunoglobulin to albumin ratios in serum and BAL fluids showed that the initial peak of proteins in the lavage was a result of serum leakage and the subsequent peak was due to local secretion of immunoglobulins. These results suggest that in addition to marked BAL cellular reactivity, N. brasiliensis infection induces an initial vascular and endothelial permeability in the respiratory tract which is soon repaired but followed by local synthesis and secretion of IgG and IgA in the lower respiratory tract.