Failure of actin cloud formation by T cells from ADAP-KO mice. (A) Quantification of T cells with actin cloud formation upon stimulation with immobilized anti–LFA-1 Ab from wild-type (WT) and ADAP-KO mice. The percentage represents T cells with actin clouds among T cells with LFA-1–induced spreading. (B) Quantification of T cells with cell spreading upon stimulation with immobilized anti-CD3 Ab. Data in A and B represent the mean ± SD of 500 cells each in 3 experiments. (C) Confocal analysis of representative cells in panels A and B. Splenic T cells from wild-type (WT) and ADAP-KO mice were unstimulated (Unstim) or stimulated with immobilized anti–LFA-1 or anti-CD3 Ab. White arrow indicates the actin cloud. For panels A and B, more than 500 cells were analyzed.