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Interferon-gamma (IFN-gamma) is a key regulator of the development and functions of the immune system. In particular, this cytokine plays a major role in immune defense against infections by various human pathogens and polymorphisms in the IFN-gamma gene, including the transcription regulatory region, and might affect host resistance to infectious agents such as schistosomes. In this study on the genetics of human schistosomiasis we uncovered three new single nucleotide polymorphisms in the IFN-gamma genes. Two polymorphisms are located in the third intron and the third is in the 3'UTR region of this gene: an A to G transition at position +2109 from the transcription start and two G to A transitions at positions +3810 and +5134. In a SUDANESE population living in an endemic area of malaria and schistosomiasis, the allelic frequenciesare: 0.85 (+2109A), 0.15 (+2109G), 0.92 (+3810G), 0.08 (+3810A), (+5134G) and 0.04 (+5134A).

Two new single-nucleotide polymorphisms are described within the human interferon gamma (IFN-gamma) promoter in a Sudanese population. One is a G to T transition at position -183 from the transcription start. The other is a A to G transition at position -155. Allelic frequency analysis indicated frequencies of 0.927 (G) and 0.073 (T) at position -183 and 0.977 (A) and 0.023 (G) at position -155. These two polymorphisms have not been detected in the Centre d'Etude du Polymorphisme Humain (CEPH) reference population. The polymorphism -183(G-->T) may alter the AP-1 binding domain and the regulation of transcription. The polymorphism -155(A-->G) is located close to the nuclear factor-activated T-cell site (NFAT site) (-168 TAAAGGAAA-160) and may affect the stability of this region.