Caucasian Origin of Disease Associated HLA Haplotypes in Chinese Blood Donors with IgA Deficiency

Purpose Selective immunoglobulin A deficiency (IgAD) is the most common primary immunodeficiency in Caucasians with a prevalence of 1:600. However, the prevalence of IgAD is markedly lower in East Asian countries but no genetic studies have been performed on IgAD individuals in the Mongoloid population. Methods We investigated the prevalence of IgAD in a large number of Chinese blood donors (n= 39,015) in Shanghai, China. We measured immunoglobulin class, IgG subclass and anti-IgA serum levels among the IgAD donors. These donors were subsequently tissue typed and the allele frequency was compared with the Shanghai bone marrow donor HLA registry. Results Seventeen IgAD Chinese blood donors were identified, giving a prevalence of 1:2,295. Two previously identified IgAD blood donor samples were added in the subsequent tests. Most IgAD donors had serum IgG levels above the normal range with no major IgG subclass deficiency and one donor was weakly positive for anti-IgA. Two-thirds of the Chinese IgAD donors carried Caucasian IgAD associated risk haplotypes, including DRB1*0301-DQB1*0201, DRB1*0701-DQB1*0202 and DRB1*0102-DQB1*0501, giving a significantly higher frequency of these haplotypes as compared to the Shanghai bone marrow donor HLA registry. Conclusions The prevalence of IgAD in Chinese in this study is markedly lower than in Caucasians. This is the first study to investigate the genetics of IgAD in the Mongoloid population and two-thirds of the Chinese IgAD donors showed a mixture of Caucasian IgAD risk haplotypes. The low prevalence of IgAD could potentially be due to the low frequency of the disease associated risk haplotypes in China.