MSCs that adhered to spot slide bottoms were fixed with -20°C methanol (100%) for 5 min. Cells were then rehydrated in PBS for 5 min at room temperature, washed three times with PBS, blocked with 3% bovine serum albumin in PBS, and incubated overnight at 4°C with SH2 (American Type Culture Collection [ATCC], Rockville, VA, USA) as a positive control. Primary antibody (SH2) was removed by washing three times with PBS, and cells were then incubated with fluorescein isothiocyanate (FITC)labeled affinity-purified antibody to mouse IgG + IgM (H + L) (DiNonA Inc., Seoul, Korea) for 1 hr at room temperature. Secondary antibodies were removed by washing three times with PBS. Coverslips were mounted onto slides with a solution containing 50% PBS and 50% glycerol. Labeled cells were observed under an Axiovert 200 (Zeiss, Thornwood, NY, USA).