Figure 1.

VLA-4/VCAM-1 interaction increases the adhesion of B cells to target membranes. (A) Differential interference contrast (DIC) and IRM images of 3-83 naive B cells settled onto planar lipid bilayers containing p31 antigen (100 molec/μm², top panels; 25 molec/μm², bottom panels) in the presence or absence of ICAM-1 (50 molec/μm²), VCAM-1 (50 molec/μm²) and/or neutralizing anti-mouse α4 mAbs. Scale bar, 5 μm. (B) Naive 3-83 B cells were evaluated for their capacity to form tight contacts on membranes loaded with p31 in the presence or absence of ICAM-1 or VCAM-1 at 50 molec/μm². After 5–10 min, images were collected at each of the specified antigen densities and the number of cells showing tight contacts was determined. Data are representative of four different experiments. (C) Quantification of the area of B-cell contact with membranes containing p31 antigen at the indicated densities in the presence or absence of ICAM-1 or VCAM-1 at 50 molec/μm². Data represent the mean of 40 cells in each case.