Primary immunodeficiency syndromes

Several DNA repair pathways have evolved to recognise and repair DNA damaged by exogenous and endogenous agents, in order to maintain genomic integrity. Defects in these pathways can lead to replication errors, loss or rearrangement ofgenomic material, mutation or cancer and eventual death. The creation of many diverse lymphocyte receptors to identify potential pathogens has evolved by breaking and randomly resorting the gene segments coding for antigen receptors. Subsequent steps utilise the ubiquitous repair proteins. Individuals with defective repair pathways are increasingly recognised with immunodeficiency, many of whom exhibit radiosensitivity. Our understanding of the role of repair proteins in the development of adaptive immunity by VDJ recombination, antibody isotype class switching and affinity maturation by somatic hyper-mutation has made significant progress over the last few years, partly by the identification of new genes involved in human disease. We describe the mechanisms involved in the development of adaptive immunity relating to DNA repair and describe the clinical consequences and treatment developments of primary immunodeficiency resulting from such defects.