Defective assembly of the IS in ARPC1B-deficient T lymphocytes. (A) Confocal images of T cells from a HC and P1, P2, and P7 adhering to ICAM1/anti-CD3 Ab-coated slides and stained for F-actin, ARPC1B, α-tubulin, and DAPI. Images representative from 1 out of 3 experiments. (B) Quantification of the area of individual cells interacting with ICAM1/anti-CD3 Ab. Median bar with minimum-maximum. Red lines: median average for HD and patients. %: Mean percentage of the medians between patients and HDs. Results of 2 independent experiments. (C) Distribution of T-cell morphologies according to the indicated subtypes: cell without protrusion, emission of filopodia, or assembly of a circular lamellipodia. (D) Representative confocal images of control T cells or T cells from P1, P2, and P7 upon interaction with P815 that have been precoated or not with anti-CD3 Ab. Fixed conjugates were stained for F-actin, ARPC1B, and DAPI. Representative images from 1 out of 2 experiments. (E) Quantification of the proportion of T cells engaged in conjugates with P815 targets precoated or not with anti-CD3 Ab. Conjugate formation was assessed at the indicated time points upon cell mixture. Results of 2 independent experiments.