[Ca²⁺]_i elevations in platelets adhering to collagen type VI under flow. Human blood cell suspensions (Figure 1 legend contains details) were perfused at the shear rate of 250 seconds over immobilized collagen type VI (coating solution 350 μg/mL) without or with prior incubation with the indicated antibodies (Figure 1 legend contains details). (A) Typical α-like (short-lasting) and γ-like (long-lasting) [Ca²⁺]_i peaks were observed. (B) Firmly adherent platelets, calculated as described in “Measurement of Ca²⁺ mobilization in adhering platelets.” (C) Activated platelets, calculated as described in the legend to Figure 2. Data are the mean ± 95% CI of at least 8 different experiments. Significant difference from platelets treated with the anti-αIIbβ3 antibody: *P < .05; **P < .01; ***P < .001.