KL-induced Ca²⁺ influx is impaired in the absence of WASP. Three independent BMMC cultures from wt or WASP-deficient mice were obtained, and cells were prepared and labeled for measurement of [Ca²⁺]_i, as described in “Measurement of Kit-induced changes in the intracellular Ca²⁺ concentration.” The real-time KL-induced changes of [Ca²⁺]_i in 3 wt (■) or 3 WASP-deficient BMMC cultures (▩) were analyzed by flow cytometry over 5 minutes (A). In a variant experiment, KL-induced changes of [Ca²⁺]_i were analyzed in wt or WASP-deficient BMMCs either in the presence (bold lines) or absence of EDTA/EGTA (dotted thin lines; B). Immobilization of extracellular Ca²⁺ by EDTA/EGTA allows the separate analysis of changes in [Ca²⁺]_i through the emptying of intracellular stores alone.