The polymerase chain reaction.

The polymerase chain reaction (PCR) is a novel technique that amplifies specific sequences with remarkable efficiency. Repeated cycles of denaturation, primer annealling and extension carried out with the heat stable enzyme, Taq polymerase, leads to exponential increases in the target DNA sequences. The technique has been widely applied in immunology to define HLA polymorphism, T-cell receptor and immunoglobulin diversity, pathogen detection, quantification of lymphokines and lymphoma or leukaemia detection. In addition, it has been very widely applied in all areas of molecular biology and human genetics. Because of its simplicity and sensitivity, PCR represents a major technical development for molecular biologists and will continue to have a great impact on molecular immunology. This review by John Bell describes the basic PCR technique and some variations on it and briefly explores their uses in molecular immunology.