Thomas W. Wells

Stable clones of 31 mouse hybridomas that produce monoclonal antibodies (MAbs) against human IgG antigenic determinants were obtained. The number of hybridomas of different specificity described are: 2 anti-IgG1 Fc, 1 anti-IgG2 Fc, 1 anti-IgG2 Fd, 2 anti-IgG3 Fc, 2 anti-IgG3 hinge, 3 anti-IgG4 Fc, 3 anti-IgG4 Fd, 2 anti-nG4m(b), 4 anti-IgGFc, 2 anti-IgGFd, 1 anti-kappa, 1 anti-lambda, 1 anti-non IgG1, 2 anti-non IgG2, 2 anti-non-IgG3, 2 anti-non-IgG4. Evidence is presented validating their specificity. Some MAbs demonstrated to be avid, potent, and specific for well defined IgG-subclass epitopes may be partially or completely inactive in other assay systems, presumably because of different presentations of antigen epitopes. In general, this problem requires careful writing of protocols describing the use of MAbs.

Under the auspices of the Ad Hoc Committee on Reference Preparations for Serum Proteins of the Standards Committee of the College of American Pathologists (CAP), and the Centers for Disease Control, Public Health Service, U. S. Department of Health and Human Services, 24 collaborators, including many experts from commercial firms that furnish the reagents and working curve calibrators actually used by most clinical laboratories in the United States, have cooperated to assign reliable values of mass and international units to 12 analytes in two freeze-dried reference preparations: The U. S. National Reference Preparation for Human Serum Proteins and the CAP Reference Preparation for Serum Proteins. The analytes estimated were: albumin, a-1-acid glycoprotein, α-1-antitrypsin, α-2-macroglobulin, ceruloplasmin, C3, C4, IgG, IgA, IgM. haptoglobin, and transferrin. Individual collaborators used single radial immunodiffusion, electroimmunodiffusion (rocket assay) rate nephelometry, end-point nephelometry, immunofluorometric assay, and enzyme immunoassay. No method-associated bias was observed in this study, but different collaborators who used the same “local” calibrator with different methods obtained results that were in closer agreement. Overall, the average among collaborator coefficient of variation of the estimated analyte concentrations was 15.9% for concentrations derived from “local” calibrators and 8.9% for concentrations that related to use of a common calibrator. The mean estimates (mass and international units) of this study provide the most practical current consensus estimates of the “true” values for these analytes in these preparations. Consequently, these mean estimates were assigned to these two generally available preparations which now can be used to provide an accuracy base to unify interlaboratory results.

The serum concentrations of 11 Ig isotypes (IgG, IgG1, IgG2, IgG3, IgG4, IgA, IgA1, IgA2, IgM, IgD, and IgE) were measured in four relatively small groups of homosexual (or bisexual) males. All these patients were seropositive for HIV. Two of the groups (nonprogressors) were clinically stable for approximately 2 years and were characterized either as asymptomatic or with PGL. The third group (progressors) developed AIDS 2-38 months after blood specimens were taken. The fourth group had AIDS. A fifth group of anti-HIV-seronegative heterosexual males completed the study. The geometric mean IgA serum concentration was more markedly elevated over normal control sera than any of the other study groups and was the only Ig isotype that was significantly higher in the progressor than in the nonprogressor group. The geometric IgG1 serum concentration was significantly higher in asymptomatic nonprogressors, PGL-nonprogressors, progressors, and AIDS patient groups than that in HIV-seronegative normals. In contrast, the geometric mean IgG2 serum concentration is depressed in all the anti-HIV-seropositive patients (but not significantly with the AIDS group). Multivariate analysis showed the Ig-isotype assays to have much less predictive power for progression to AIDS than the T-helper cell assays.