Influence of molecular size of IgA on its immunoassay by various techniques. III. Immunonephelometry

Abstract

The influence of size heterogeneity of [human] IgA on its immunonephelometric (IN) assay was studied using highly purified preparations of monoclonal (MC) or polyclonal (PC) monomeric (M), dimeric (D), trimeric (T) and tetrameric (Q) IgA, and of secretory IgA (sIgA). Concentrations measured by optical density (OD) were compared to IN (concentrations obtained by using M as standards, on an equal weight basis). No significant difference was found between OD and IN concentrations of D. T, Q and sIgA were only slightly underestimated, with correction factors (CF) of 1.16, 1.20 and 1.24, respectively. The value of 1.24 for the sIgA sample (84% of 11S, 16% of 15S) could be due to the fact that secretory component represents .apprx. 20% of the mass of the sIgA molecule. IN seems a method of choice for measuring IgA concentrations in the range of .mu.g/ml, almost independently of the size of IgA.