Involvement of integrins in human intestinal mast cell adhesion.

(A) Integrin mRNA expression. RT-PCR was performed with RNA derived from mast cells directly after their isolation (purity, 95%) or with RNA from mast cells after culture in the presence of SCF (purity, 99% or greater). DNA amplifications with specific primer pairs were separated on a 1% agarose gel. M indicates 100-bp DNA ladder. (B) Blocking of integrin subunits. Cells were preincubated for 10 minutes at 37°C with an isotype control or blocking mAbs directed against the integrin subunits β1(CD29), β2 (CD18), and αVβ3 (CD51). Adhesion of mast cells to fibronectin (FN) is expressed as percentage of control, whereas adhesion of mast cells preincubated with isotype control was set at 100% (means ± SD, n = 3). (C) Effect of SCF and mAb 29C6 on HUTS-21 β1 epitope expression. Cells were incubated with SCF or 29C6, each at 100 ng/mL (54 nM or 6.5 nM), for 60 minutes or with buffer control before analysis of the expression of the HUTS-21 epitope presented on an activation-dependent confirmation of β1. Isotype control staining is shown in gray. Full lines show antibody staining (right peak). Results of 1 of 3 representative experiments are shown. Mast cell purity was 98% or greater.