IL-4–stimulated macrophages engage in homotypic and heterotypic interactions through E-cadherin. (A) A5 KLRG1-reporter cells were cocultured overnight with differentially stimulated Cdh1^F/F control or Cdh1^Δ thio-PEMs, and the percentage GFP⁺ reporter cells was determined by FACS. Data are mean ± SEM of 3 individual mice. (B) CD103⁺ CSFE-labeled MTC-1 cells were cocultured with untreated or IL-4–treated Cdh1^F/F control or Cdh1^Δ thio-PEM monolayers, which were either pretreated or not with ECCD2 antibodies. After 45 minutes, nonadherent cells were washed away, and the number of remaining MTC-1 cells was determined by fluorescence measurement. Data were plotted as the percentage change in the number of MTC-1 cells adhering to IL-4–treated thio-PEMs compared with untreated thio-PEMs. Mean ± SEM of 6 wells is shown for one representative experiment. (Ci-iii) Equal numbers of DiI (red) and DiO (green) labeled Cdh1^F/F control (a-d) or Cdh1^Δ (e-h) thio-PEMs were cultured for 24 hours with (b-d,f-h) or without (a,e) IL-4 on Permanox plastic and imaged by confocal microscopy. Volocity analysis software was applied to create a red/green colocalization channel (Ci). The average volume of colocalized voxels per object (Cii) and the amount of nuclei per fused cell (Ciii) were calculated. Data are mean ± SEM of 5 fields. **P < .01.