C3b-stabilizing antibody (3E7) enhances the inhibition of NK-cell CD16 down-modulation and CD54 up-regulation. PBMCs and Raji cells were mixed at a 1:1 ratio for 20 hours in the presence or absence of 50% serum with varying concentrations of rituximab and 10 μg/mL of 3E7. Surface marker expression was determined using flow cytometry with gating on CD3⁻, CD56⁺ lymphocytes. NK-cell CD54, expressed as a percentage of CD54 bright, was cultured in media, serum, or serum plus 3E7 (n = 3). Error bars represent SD of the mean.