Multiple cell determinants are effectively camouflaged by cell surface derivatization with mPEG. Shown are the scatter plot analyses for CD28 (A) costimulatory molecule present on T cells, binds to CD80; CD3 (B) associated with TCR on T cells and is necessary for signal transduction; CD4 (C) coreceptor for MHC class II molecules present on T cells); and CD80 (D) costimulatory molecule present on B cells and APC. Lane 1 represents the control unmodified PBMC; lane 2 represents the same PBMC population modified with 2.4 mmol/L mPEG (cell concentration of 4 × 10⁶); while lane 3 represents the appropriate isotype control for the sample. In all cases, mPEG modification resulted in a significant decrease (P < .001) in antibody detection of the indicated cell marker. This decrease in antibody detection occurs in a dose-dependent manner upon increasing modification with mPEG (data not shown).