Frozen slides were thawed at room temperature. Cells were fixed by incubating slides in 4% formaldehyde (Catalog No. 16220; Electron Microscopy Sciences; Fort Washington PA)-PBS for 15 min at room temperature to fix cells. After three washes in PBS, slides were incubated in 1% H2O2 (H-1009; Sigma Chemical)-PBS 10 min at room temperature, washed three times in PBS, and stained. Slides were permeabilized by incubation with 0.5% saponin (S-2149; Sigma Chemical)-PBS for 10 min at room temperature. Slides were then washed thrice with PBS-0.05% Tween 20–0.01% Thimerosal (T-5125; Sigma). Once the cells were permeabilized, the same buffer was used after this step. According to the protocol of the Vectastain Elite ABC kit (Catalog No. PK-6102; Vector Laboratories; Burlingame, CA), slides were incubated for 20 min at room temperature in blocking solution (5% horse serum-PBS for uPAR, PAI-1, CAP18, IL-8 CD14, and cytokeratin; 5% goat serum for CD15) and washed thrice with PBS. Slides were then incubated in avidin blocking solution (Catalog No. SP-2001; Avidin/Biotin Blocking Kit; Vector Laboratories) for 15 min at room temperature, washed thrice with PBS for surface staining, and then washed in PBS-0.05% Tween 20–0.01% Thimerosal for cytoplasmic staining. Slides were then incubated with biotin blocking solution for 15 min at room temperature and washed thrice with PBS-0.05% Tween 20–0.01% Thimerosal. Following this preparation, slides were incubated with primary monoclonal antibody (for uPAR, Catalog No. 3936; American Diagnostica; Greenwich, CT; for PAI-1, Catalog No. 3785; American Diagnostica; for CAP18, see primary antibody, ELISA methods above; for IL-8, Catalog No. 554717; BD Pharmingen mouse IgG2b clone G265–8; for CD14, Catalog No. 555396; BD Pharmingen; and for cytokeratin, Catalog No. 349205; BD Pharmingen) each diluted in 5% horse serum-1% BSA-0.05% Tween 20-PBS. For CD15, the antibody (Catalog No. 555400; BD Pharmingen) was diluted in 5% normal goat serum-1%BSA-0.05% Tween 20-PBS. Slides were incubated with primary antibody for 60 min at room temperature, and washed five times with PBS-0.05% Tween 20–0.01% Thimerosal. An isotype control antibody was run with each experiment (mouse IgG isotype control; Catalog No. I-2000; Vector Laboratories). For staining uPAR, PAI-1, CAP18, IL-8, CD14, and cytokeratin, reactions were developed with biotinylated horse anti-mouse antibody (Catalog No. PK-6102; Vector Laboratories) diluted in 5% horse serum-1% BSA-0.05% Tween 20-PBS. For staining CD15, the reaction was developed with biotinylated goat anti-mouse antibody (Catalog No. PK-6102; Vector Laboratories) diluted in 5% goat serum-1% BSA-0.05% Tween 20-PBS. Slides were incubated for 30 min at room temperature and washed five times with PBS-0.05% Tween 20–0.01% Thimerosal. For development, slides were incubated for 30 min at room temperature with Vector ABC reagent (Catalog No. PK-6102; Vector Laboratories) prepared in PBS 30 min before use and then washed thrice in PBS. Color was developed (3,3′-diaminobenzidine peroxidase substrate; Catalog No. SK-4100; or Vector VIP [peroxidase substrate, Catalog No. SK-4600; Vector Laboratories]) according to manufacturer’s instruction. Color development was stopped by washing in distilled water, the slides were air dried, and the slides were viewed under microscope to assess the positive staining cells and determine cell type by comparing with Wright-Giemsa–stained slides (Hema 3 set, Catalog No. 122–911; Biochemical Science; Swedesboro, NJ).