For publications, we use isotype controls for monoclonals and rabbit
immunoglobulins for polyclonals (supplied by company D). These are run
for each block. For diagnostics, we replace the primary with TBS,
again for each block. This gives some data regarding the affinity of
the secondary for the test tissue, different for each block. We have
found this approach to be useful particularly when following heat
mediated antigen retrieval (possible exposure of biotin) where we use
a biotin block on a repeat run if we have a positive negative control.
So far this seems to solve all the problems. This difference in
approach is mainly due to cost and time available. It appears to be a
practical solution to a complex situation.

Perry Maxwell
Royal Group of Hospitals Trust,
Belfast, N. Ireland