Jacob, G.L.

Abstract We compared the quantities and avidities of IgE and IgG antibodies from three phospholipase-A (PLA) sensitive patients during honeybee venom immunotherapy. IgG antibody was purified by affinity chromatography through a Sepharose anti-IgE Column followed by ionexchange chromatography on DEAE Sephadex. IgE antibody was obtained by elution from the Sepharose anti-IgE column with 4 M guanidinium HCl and by passage of the eluate over Sepharose anti-IgG. Absolute amounts of IgE and IgG antibody to PLA were determined by immunoabsorption and radioimmunoprecipitation, respectively. IgE antibody to PLA accounted for 25.1% to 28.7% (X̄ = 27.0%) of the total IgE protein; IgG antibody accounted for 0.073% to 0.210% (X̄ = 0.130%) of the total IgG protein. The relative avidities of IgE and IgG antibodies were assessed by the ability of equimolar amounts to bind radioiodinated PLA. In two patients, avidities of IgE and IgG antibody for PLA were comparble, whereas in the third, IgG antibody bound PLA more avidly than IgE antibody. The valence of IgE antibody was greater than 1.9, assuming that PLA behaved as a univalent ligand in extreme antigen excess. IgG antibody was able to inhibit binding of IgE antibody in the PLA radioallergosorbent test (RAST) from 10% to 40% at a molar excess of 10- to 1000-fold. The results indicate that: 1) IgE antibody to PLA accounts for a high percentage of total IgE protein; 2) the avidities of IgE and IgG antibodies are similar (two of three patients); 3) the valence of IgE antibody approaches two; and (4) IgG antibody can interfere with the measurement of IgE antibody in the PLA RAST.

The quantities of immunoglobulin E (IgE) antibodies to grass or ragweed allergens were measured by an immunoabsorption in the serums of patients sensitive to one of these allergens. IgE antibodies to grass or ragweed allergens accounted for means of 30 and 29 percent of the total IgE protein. After the ragweed pollination season, the levels of serum IgE antibodies to ragweed allergens rose dramatically and in postpollination serums they accounted for 39 percent of the total IgE protein with a range from 13 to 50 percent.

Summary Serum and plasma are used interchangeably to measure anti-neutrophil cytoplasmic antibodies (ANCA), even though the release of ANCA target antigens during the preparation of serum could affect ANCA assays and cause discrepancies between the results obtained from serum and plasma. To what extent ANCA test results obtained from serum agree and correlate with results from plasma remains unknown. Therefore, a comprehensive comparison was performed using serum and plasma samples which were collected in 175 patients with active Wegener's granulomatosis at enrolment of a recent randomized trial. These paired serum and plasma samples were subjected to parallel ANCA testing by standard indirect immunofluoresence on ethanol-fixed neutrophils, a direct enzyme-linked immunoassay (ELISA) for proteinase 3 (PR3)-ANCA and myeloperoxidase (MPO)-ANCA, and two different capture ELISAs for PR3-ANCA. The concordance of categorical serum and plasma ANCA results was assessed using κ-coefficients. These were > 0·8 for all assays, indicating a very good concordance between positive and negative serum and plasma results. Spearman's correlation coefficients for serum and plasma PR3-ANCA values obtained by direct ELISA and both capture ELISAs were ≥ 0·95 (P < 0·0001). Our study shows that serum and plasma samples can be used interchangeably for measuring ANCA.