We been using a "mouse anti-rat macrophage" from Pharmagen.  We
incubated the rat tissue (lung) for 1 hour at 10 and 20 micrograms per
ml.  I also pretreated the tissue with and without antigen retrieval.  I
used Pharmagen's goat anti-mouse with minimal cross-reactivity to rat.
However, we are not getting any staining.

Could someone help me with a procedure, or technical hint; or another
perhaps another rat macrophage antibody that works in formalin-fixed
paraffin embedded tissues?

My main concern is that the secondary antibody may not recognize the
primary antibody.

Has anyone ever heard of MOMA?