EVIDENCE FOR MULTIPLE GENETIC SUSCEPTIBILITY LOCI FOR ASTHMA

Genetic susceptibility to asthma is due to multiple genes that interac t with each other and the environment. There are many known environmen tal influences, such as viral and other respiratory infections and exp osure to allergens, air pollutants, and active or passive cigarette sm oke (1). Genome-wide screens for asthma and atopy have been completed and show statistical evidence for linkage in different racial groups a nd population samples (4, 5). Some of these linkages have already been replicated in different studies, and most of them are in chromosomal regions containing relevant candidate genes that may regulate inflamma tory processes including cytokine synthesis, T-cell responses, or othe r immune functions. These associations support the relevance of this g enetic approach in understanding susceptibility to and expression of a sthmatic and allergic phenotypes. Once specific sequence variants are identified, it will become important to test for gene-environment inte raction in order to understand the significance and relative effect of each gene on the overall phenotype.