Assessment of IgA subclasses synthesis in children with selective and partial IgA deficiency

The aim of this study was to determine the failure degree of IgA1 and IgA2 synthesis in 21 children with selective IgA deficiency (IgAD) and in 8 partial IgA-deficient children (p-IgAD). Serum and secretory (salivary and fecal) levels of IgA subclasses were assessed by means of ELISA methods. Both IgA1 and IgA2 were detectable in all serum samples but only the concentration of IgA2 increased with increasing age. The significantly lower values of serum IgA1 and IgA2 were shown in IgAD children as compared with p-IgAD children (p < 0.0001 for IgA1 and p < 0.005 for IgA2) as well as with the control group (p < 0.0000001). The level of serum IgA1 was considerably decreased in p-IgAD group in comparison with the healthy controls (p < 0.00005), whereas no statistically significant differences in this parameter were detected between p-IgAD and IgAD groups. Moreover, the concentrations of IgA2 were on the level of control group in 75% of sera from IgAD group and in almost 10% of sera from p-IgAD group. On the other hand, the observation of negative correlation between the percentage of the IgA1 in the total serum IgA and the percentage of the IgA2 in the total serum IgA in IgAD group may prove the compensative role of each other. Diminished IgA1 synthesis indicated in part p-IgAD group, together with normal values of both S-IgA subclasses and serum IgA2 may reflect the transient defect of IgA synthesis in such children followed by an increase and normalization of serum IgA level or a decrease and absence of immunoglobulin. Concluding, the systemic IgA1 synthesis was more impaired than the IgA2 production in the two tested groups of IgA-deficient children. An increase in serum IgA2 concentration to the normal range may suggest that either among these children there are cases with selectively impaired synthesis of only one subclass or that there are factors, which independently regulate the synthesis of serum IgA1 and IgA2.