Objectives To assess the value of serum interleukin (IL) 13 levels as an immunological marker in atopic upper respiratory diseases, to clarify its differences in atopic and non atopic bronchial asthma and to determine the role of an IL-13 R α₁ gene single nucleotide polymorphism (SNP) (A1398G) in the pathogenesis of these diseases.

Methods Seventy-five patients were compared with 25 age-matched healthy volunteers. Serum total immunoglobulin (Ig) E and IL-13 levels were measured by enzyme-linked immunosorbent assay and the IL-13 R α₁ gene (A1398 G) was screened by specific polymerase chain reaction.

Results There was a non significant association between G allele frequencies of the IL-13 R α₁ (1398) gene polymorphism as compared to in controls. There were a significant increase in the serum level of total IgE & IL-13 towards heterozygous AG and homozygous GG than homozygous AA in atopic asthma, non atopic asthma, and allergic rhinitis patients. There was a significant increase in the serum level of total IgE & IL-13 towards homozygous GG than heterozygous AG in atopic asthma non atopic asthma, and allergic rhinitis patients for IgE and in all groups for IL-13.

Conclusion interleukin-13 receptor α 1 subunit gene A1398G polymorphism does not contribute to asthma or allergic rhinitis susceptibility, although the interleukin-13 receptor α 1 subunit gene locus might be involved in the control of immunoglobulin E production, IL13 can used as an immunological marker in atopic upper respiratory diseases and to differentiate between atopic and non atopic bronchial asthma.