Ethnicity-specific gene-gene interaction between IL-13 and IL-4Ralpha among African Americans with asthma.

Rationale: Genes in the interleukin (IL)-4/IL-13/IL-4Ralpha pathway have been shown to be associated with asthma and related phenotypes in some populations, but not in others. Furthermore, interaction between these genes has been shown to affect asthma in white and Chinese populations.

Objectives: To determine whether there are IL-4/IL-13 and IL-4Ralpha gene-gene interactions that are associated with asthma in African Americans.

Population stratification confounds genetic association studies among Latinos.

In the United States, asthma prevalence and mortality are the highest among Puerto Ricans and the lowest among Mexicans. Case-control association studies are a powerful strategy for identifying genes of modest effect in complex diseases. However, studies of complex disorders in admixed populations such as Latinos may be confounded by population stratification.