or jnk schmitz j et al immunity 23 479 490 2005 in this assay cells e g hek293ft cells are transfected with either a mock expression vector or with an expression vector encoding st2 and incubated with il 33 in the control experiment no test molecule is added to the incubation in the test experiment the molecule to be tested for its ability to inhibit il 33 signal transduction is added cellular extracts are prepared and blotted with anti phospho erk1 2 anti phospho p38 anti phospho i u03bab u03b1 or anti phospho jnk antibodies a decrease in the level of phosphorylated erk1 2 p38 i u03bab u03b1 or jnk in extracts from il 33 treated cells when incubated with the test molecule indicates that the test molecule is an antagonist of il 33 binding to the il 1racp receptor complex another in vitro assay that can be performed is to assay for phosphorylation of nf u03bab erk1 2 or p38 in cells that naturally express st2 e g mouse mast cells wtmc schmitz j et al immunity 23 479 490 2005 in the control experiment wtmc cells are incubated with il 33 but no test molecule is added to the incubation in the test experiment cells are incubated with il 33 and the molecule to be tested for its ability to inhibit il 33 signal transduction cell lysates are separated by sds page and electroblotted cellular extracts are blotted with anti nf u03bab anti phospho erk1 2 or anti phospho p38 antibodies a decrease in the level of phosphorylated nf u03bab erk1 2 or p38 in extracts from.