2. Washing of the cells2.1 .Hypertonic ShockIf the pellet is contaminated with erythrocytes, then carry out a hypertonic shock" as follows.Resuspend the pellet in 2mL sterile or distilled water and incubate for 50-60 seconds.To restore the normal osmolarity, add 2x PBS to the suspension. After that dilute the suspension with 1 x PBS or culture medium (AIM-V/RPMI) to 20一30mL and centrifuge the suspension again at 465g for 15 minutes.If the BAL is contaminated with many red blood cells a density gradient centrifugation similar to the density gradient centrifugation used in the standard T-SPOT.TBTest can be performed.