CD43-stimulated T lymphocytes recruit additional cells through the uropods. (A) T lymphoblasts adhered to petri dishes coated with ICAM-1-Fc were treated with the anti-CD43 HP2/21 MoAb. A second layer of untreated T lymphoblasts (bright cells) was then added and cell-cell interactions were recorded by videomicroscopy for 30 minutes. Black arrowheads point to transported cells; white arrowheads point to cellular uropods of cells from the first cohort, whereas white arrows point from cellular leading edges. (B) Quantitation of T-cell lymphocyte recruitment mediated by anti-CD43 polarized cells. T lymphoblasts were allowed to adhere to plastic petri dishes coated with ICAM-1-Fc for 30 minutes at 37°C in the presence of the proaggregatory anti-CD43 (HP2/21 and TP1/36) and anti-ICAM-3 (HP2/19) MoAb or the control anti-HLA-A,B W6/32 MoAb. After the addition of a second layer of cells, cell-cell interactions were recorded for 1 hour, and the recruitment index was calculated as the number of cells of the second layer contacted per cell number adhered to the substrate.