Lactic acid does not alter surface antigen profile in CTLs. CTLs were treated for 24 hours with 20 mM lactic acid or were left untreated. After staining with the indicated mAbs, the phenotype of CTLs was determined by FACS. Grey indicates isotype control of untreated cells; dotted line, control; and solid line, with lactic acid. Results are representative of 3 independent experiments.