Identification of missense mutation in the IL12B gene: lack of association between IL12B polymorphisms and asthma and allergic rhinitis in the Japanese population.

Interleukin-12 (IL-12) is a macrophage-derived cytokine that modulates T lymphocyte responses and can suppress allergic inflammation. In a genome-wide screen, we found strong evidence for linkage of atopic asthma with marker D5S1352, located close to IL12B, with a maximum lod score of 4.34. We screened for mutation in IL12B and found three novel (-4475-4insG, Glu186Asp and Ser226Asn) variants and one previously reported (1188A>C) variant in IL12B, and conducted transmission disequilibrium tests in families identified through children with atopic asthma or allergic rhinitis. Frequencies of the Asn226 and 1188C alleles in the parents were 0.04 and 0.5, respectively. Preferential transmission of either the Ser226/Asn226 or 1188A/C allele to asthma-affected or rhinitis-affected children was not observed (P > 0.1) and was not associated significantly with total serum IgE level (P > 0.1). Our results indicate that polymorphisms in IL12B are not likely to be associated with the development of atopy-related phenotypes.