Malnutrition and experimental lung allergy

Abstract

Although it is commonly accepted that the immune response is affected by malnutrition there are very few data about its effect in allergic diseases. The aim of the present study was to investigate the effect of malnutrition in allergic lung inflammation. An anaphylactic reaction was induced in rat lungs and the increased vascular permeability was measured in the trachea, internal and external bronchi and parenchyma by the Evans blue extravasation method. These studies were conducted in two dietary groups: one fed a normoproteic diet (18%) and the other a hypoproteic diet (4.5%). When the animals were 60 days old the group fed the hypoproteic diet presented a reduction of 77.86% in bodyweight, 63.3% in food intake and 36% in plasma protein concentration characterizing a severe protein-calorie malnutrition. The anaphylactic reaction in the lungs induced a significant increase in vascular permeability in the trachea and bronchi of both dietary groups. However, the intensity of this effect was significantly lower in the malnourished group. Analysis of immunoglobulin isotypes in the serum by ELISA showed that whereas IgG1 and IgG2a levels were similar in both groups, the levels of IgE were significantly lower in the malnourished animals. Moreover, the levels of antigen-specific IgG1, IgG2a and IgE were all significantly inhibited by the protein-calorie malnutrition. When antibodies were passively transfered to the malnourished rats, they developed a reaction as intense as the normoproteic group. These results suggest that the capacity to release inflammatory mediators and the vascular response to these mediators is not affected by this type of malnutrition and, therefore, the diminished response of the airways reported here is probably due to the lower levels of anaphylactic antibodies produced by the malnourished rats.