An investigation of inflammatory cells in asthma as studied by immunocytochemical techniques on bronchial biopsies

The pathological evidence for airways inflammation in asthma has been acknowledged since the first investigations of the disease in patients who died in status asthmaticus. The advent of fibreoptic bronchoscopy has revolutionised the study of the pathology of asthma by providing a suitable tool for the acquisition of samples from the airways of living asthmatics with milder disease. Immunocytochemistry is a powerful tool for the demonstration of specific antigens and facilitates the labelling of distinct populations of cells within tissue sections. This thesis describes two protocols for the processing and embedding of bronchial biopsies into resin which were subsequently used for the demonstration of antigens by the application of suitable immunocytochemical techniques. Embedding tissues in resin produces sections of high quality for evaluation purposes. Both protocols allowed excellent morphological preservation and clear localisation of immunocytochemical product. This enabled confident quantitation of labelled cells within the sections and this property was utilised for the investigation of the density of inflammatory cells within the airways. Bronchial biopsies from asthmatics had a increased number of eosinophils compared with those from normal healthy individuals. An inhaled corticosteroid caused a reduction in eosinophil, mast cell and T lymphocyte numbers within the airway wall but a long-acting β2-agonist had no significant effect upon the density of the inflammatory cell population. The ability to obtain thin sections from the resin embedded biopsies allowed for the comparison of the same cell labelled for two different antigens in serial sections elucidating the type of cells positive for the cytokines IL-4, IL-5, IL-6 and TNFα. This work has contributed to the knowledge of the inflammatory cell infiltrate within the airways of asthmatics.