We performed the clinical immunology laboratory IgG subclass assay on a Siemens BN II nephelometer (Siemens Dade Behring BN II Nephelometer) with Binding Site antisera for each individual subclass and Siemens antiserum for IgG total.
This result was compared to the mean areas (14 runs) for low-concentration samples of each subclass to determine where the mean area for a specific concentration was found to be greater than the mean(blank) + 3SD(blank) and labeled as the LOD for that IgG subclass or total.
2 shows linear regression analyses comparing the calculated concentration for the total IgG found by adding all 4 subclass concentrations together to the concentration determined by use of the total IgG standard for both the nephelometric assay and the LC-MS/MS assay.
Three of our anti IgG1, 2, 4 MAbs (1F5A8, 6F11E1 and 8F9G7), recognize conformational epitopes located to heavy chain of IgG1, 2, 4 but not IgG3 subclasses and a protein of IgG3 subclass (Goe protein) (Figure 1), a reactivity pattern similar to SPA (21).
The fourth MAb (6F19C11) in this category is completely different from the others as it does not recognize any protein of IgG3 subclass and it recognizes a linear epitope located to IgGl, 2, 4 subclasses (Figure 3).
IgG4 subclass has different amino acid sequences at positions 268, 330 and 331 in CH2 domain and positions 355, 409, 419 and 445 in CH3 domain.
The patients had two samples taken at three month-intervals for assurance of reliability of the measured parameters, in view of reported variations in normal IgG subclass levels (8).
An average of the two samples of the IgG subclass values was used to assess the incidence of deficiencies.
The associations between IgA deficiency and IgG subclass alterations are illustrated in Table 3.