If IgA is the soly isotype to be detected, its heavy chain i.e. Alpha
chain should be the primary target. As to Kappa and Lambda light chains,
they can combine with either Gamma or Mu heavy chain to form IgG or IgM,
which could be produced locally (usually in small quantity compared with
sIgA) or originated from the blood.
Best Regards,
Kefei Hu
