Raised Serum IgG4 Levels in Patients with Atopy and Filariasis: Application of an Automated Particle-Counting Immunoassay Using Monoclonal Antibody

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Abstract
We show here an automated (50 samples/h) assay for serum IgG4 having a throughput time of 40 min per sample and a sensitivity of 10 μg/ml. The assay procedure is based on the inhibition by sample of the agglutination reaction between monoclonal anti-IgG4 antibodies and latex particles to which IgG4 myeloma protein has been coupled. Assay reliability was ascertained by testing for linearity, analytical recovery (96.4%), interassay precision (≤8%), specificity and correlation between the results obtained with monoclonal and polyclonal anti-IgG4 antibodies (n = 84; rs = 0.97). Application of the assay to sera from various groups of patients indicated significantly (p < 0.00005) higher geometrical means (Gx) in patients suffering from atopy (n = 87; Gx = 617 μg/ml), atopic dermatitis (n = 28; Gx = 1,043 μg/ml), filariasis with Onchocerca volvulus (n = 48; Gx = 1,681 μg/ml) and Brugia malayi(n = 20; Gx = 1,078 μg/ml) as compared to nonatopic subjects (n = 103; Gx = 302 μg/ml) and randomized paired maternal/cord sera (n = 41; Gx = 276 and 296 μg/ml, respectively). IgG4 in the paired maternal/cord sera correlated (r = 0.98; p <0.00005). There was no significant influence of age or sex on the IgG4 levels either among the nonatopics or the atopies even though low IgG4 (≤30 μg/ml) was more common among women. The results suggest that IgG4 and IgE responses are somehow closely related in atopic and parasite-infested patients at the physiological, pathogenic or genetic level.