Reactivity of anti-IgG subclass mAbs against all possible combinations of IgG1-4 subclass protein
There are 15 possible combinations of positivity to the subclass protein (such as IgG1 alone, IgG1+2, IgG1+2+3, etc). Table 2 shows the reactivity of the different anti-IgG subclass mAbs against the 15 possible combinations of IgG1-4 subclass protein. We observed 9 distinct anti-IgG subclass mAbs reactivity pattern groups instead of the 15 expected ones if the all mAbs were monospecific. Three anti-IgG subclass mAbs patterns of reactivity corresponded to a unique combination of IgG subclass protein. The anti-IgG subclass mAbs reactivity pattern of group 1, 2, and 3 identified IgG1, IgG4, IgG1+4, respectively. In contrast, 6 anti-IgG subclass mAbs patterns of reactivity corresponded to two different combinations of IgG subclass protein. In group 4, the anti-IgG subclass mAbs pattern of reactivity reveals that the anti-IgG subclass mAbs cannot distinguish between IgG2 only and IgG1+2. Similarly in groups 5 and 6, the anti-IgG subclass mAbs pattern of reactivity shows that IgG3 only and IgG1+3, and IgG2+4 and IgG1+2+4, respectively, cannot be distinguished. Although the anti-IgG subclass mAbs pattern of reactivity in group 7, 8 and 9 can be distinguished, the differences lies in the MFI intensity, which can be challenging to point out, particularly if the concentration of the IgG subclass protein is high. It is important to note that the monospecificty of anti-human-IgG3 mAb (clone: HP6050) implies that positivity indicates the presence of IgG3 proteins. Last, using clones HP6001, HP6014, HP6050 and HP6025/HP6023 can distinguish the 9 pattern of reactivity detected with all the anti-IgG subclass mAbs tested.