Application of molecular biology to pulmonary disease

The techniques of molecular biology now make it possible to clone specific genes, determine the nature of their molecular message, produce their protein product, and study their function in health and disease. DNA probes, particularly those for ribosomal RNA, offer a new way for the diagnosis of infectious diseases affecting the lung, particularly TB. In addition, recombinant DNA libraries of mycobacteria can be used to isolate mycobacterial antigens recognized by patients with TB. This may allow development of better immunologic tests and vaccines. A specific chromosomal abnormality of human chromosome 3 has been found in small cell lung cancer. It is hypothesized that loss of genes from this region may play a role in the pathogenesis of lung cancer. Another important factor in development of the disease is the expression of cancer-associated oncogenes. In addition to insights into the biology of lung cancer, these oncogenes might provide a method to classify various types of lung cancer and predict response to therapy. Specialized DNA markers known as RFLPs have now been linked with CF. This has resulted in localization of the CF gene to human chromosome 7 and the detection of the gene in most of its carriers who have been studied. Knowing where the gene resides and use of techniques of genetic engineering will eventually allow isolation of the CF gene (or genes) on chromosome 11 and determination of the biochemical defect for which it codes. Similarly, the gene for human alpha 1-antitrypsin has also been cloned. A practical benefit is the production of normal and mutant enzyme for replacement therapy in patients.