Blocking of integrin β1 and β3 inhibits adhesion to α3(IV)NC1 domain. (A) Cell adhesion assay. MLECs were seeded onto a 96-well plate coated with α3(IV)NC1 in the presence of the indicated integrin antibodies and cell adhesion was evaluated. Values are means (± the standard error of the mean [SEM]) of triplicate wells. Differences between 3 independent experiments control IgG and various integrin antibodies treated cells binding were significant. *P < .05 and **P < .01. (B) Proliferation assay. Similar to panel A, cells were preincubated with indicated integrin proteins with and without α3(IV)NC1 and cell proliferation was evaluated. The results are shown as mean (± the standard error of the mean [SEM]) *P < .05, α3(IV)NC1 without vs with α3β1 and αVβ3 integrins. **P < .008, α3(IV)NC1 without vs with α3β1 + αVβ3 integrins together. (C-I) Identification of α3(IV)NC1 functional binding integrins. MLECs were treated with α3(IV)NC1 for approximately 6 hours and extracts were immunoprecipitated with anti-α3(IV)NC1 antibody or control IgG. Immunoprecipitates were fractionated by SDS-PAGE and immunoblotted with anti-α3(IV)NC1, αV, α3, β3, β1, α1, and α5 antibodies. Crude cell lysate was used as a positive control.