To detect macrophage antigen 2 (MAC-2) expressing cells, slides were stream hydrated with citrate buffer for 20 minutes. The primary antibody, rat anti-Mac-2 (TIB-166, ATCC, Mannasas, VA) was used at a 1:200 dilution followed by a biotinylated goat-anti-rat IgG secondary antibody and developed with Streptavidin HRP (Biocare, Concord, CA).