Antibody-dependent cellular cytotoxicity of human monocytes, precultured with GM-CSF for 18 hours, toward Jurkat acute T leukemia cells is enhanced by blocking anti-CD47 F(ab′)2, but intact anti-CD47 IgG induces cytotoxicity alone. Cytotoxicity was measured by the release of 51Cr from loaded target cells. (A) Surface expression of CD3 (using CLB-T3/4.2a mAb) and CD47 (using B6H12 mAb) and on Jurkat cells as evaluated by flow cytometry. (B) ADCC of human monocytes toward Jurkat cells after preincubation with mouse IgG2a T3/4.2a anti-CD3 (20 μg/mL) and/or B6H12 (10 μg/mL) anti-CD47 B6H12 F(ab′)2 or intact IgG. Values shown are means ± SD of (n ≥ 3) independent experiments. Note that intact anti-CD47 IgG alone opsonizes and induces monocyte-mediated cytotoxicity in Jurkat cells, while F(ab′)2 act only in concert with anti-CD3. P values of statistically significant differences, as determined by Student t test, are indicated.
