Inhibition of cell adhesion to SIRP1ex by SIRP-reactive MoAbs. Immobilized SIRP1ex (2 μL of 20 μg/mL solution) was preincubated for 30 minutes at 37°C with SIRP1-reactive MoAbs SE5A5, SE7C2, SE8A3, SE11A6, SE12B6, SE12C3, and P3C4 or a nonbinding control antibody. Adhesion of Jurkat cells to SIRP1ex was analyzed by incubating the cells for 1 hour in the presence of the antibodies. Specific cell binding is shown in the round protein drop and was evaluated and photographed using a Zeiss Axiovert microscope (original magnification × 40) (n = 3).