Background. Selective IgA deficiency (IgAD) is the most frequent primary immunodeficiency in Caucasians. A protective effect of an aspartic acid residue at position 57 of the DQ beta chain against IgAD has been repeatedly described. The aim of our study was to determine, whether the genetic effect of non-asparfic acids (non-Asp) at position 57 of the DQ beta chain is different in familial and non-familial forms of IgAD. Methods and Results. Codon 57 genotyping was perfonned in 59 patients with Sporadic from in 28 patients with familial forms of IgAD, and in 162 control persons. Significantly increased occurrence of the non-Asp residues at position 57 in IgAD patients compared to control persons was found, but there was no difference between familial and sporadic forms of IgAD. The association was not proved in six IgAD patients who esere relatives of CVID patients. Conclusion. The protective effect of non-aspartic acid at position 57 of the DQ beta chain is present in both sporadic and familial form of IgAD. This effect was not observed in IgAD relatives of CVID persons showing tkat a genetic background of this form might be different than in other forms of IgAD.

        Key words: IgA deficiency, variable immunodeficiency, HLA-typing, aspartic acid.