Spreading of human platelets on the immobilized extracellular domain of CD84. Washed human platelets seeded on coverslips coated with various proteins at a concentration of 50 μg/mL. Platelets were preincubated with either 5 μg/mL α-CD84 (E and F) or isotype control Fab fragment (G) prior to seeding. Pictures are representatives of experiments repeated at least 3 times in duplicate.