FIGURE 2.

Induction of protection from complement by IL-4 requires up-regulated expression of claudin-5. ECs were transfected with 2.5 nm siRNA targeting claudin-5 (three different sequences) (A), VE-cadherin (B), or β-actin (A and B), and then incubated with 10 ng/ml IL-4 for 48 h. The ECs were used to prepare cell extracts for immunoblotting or, after washing, tested for sensitivity to complement by incubation for 2 h with 20–30% human serum. Bar graphs are means ± S.E. of results from nine experiments in A and four experiments in B. *, p < 0.001, degree of cytotoxicity in IL-4-treated samples versus medium alone; **, p < 0.05, IL-4 control versus IL-4 siRNA-treated; #, p < 0.001, medium alone versus medium siRNA. The immunoblots are representative of nine independent experiments (A) and four independent experiments (B).