Ignoring specified tables on replication primary
first of all, the replication variables have effect on the slave only when activated on a replicated "slave" server. you need to understand that the filtering rules on master differ from the ones on slave. on master you can choose only to log a whole db or not. on slave you have more options. here is described http://dev.mysql.com/doc/refman/5.5/en/replication-rules.html
and here: http://dev.mysql.com/doc/refman/5.5/en/replication-rules-table-options.html
I think, you want to skip replicating a set of tables with a given pattern on slave. So, the variables must be configured on the slave. Change the configuration file on the salve and add the db_name instead of % for db part. 


  replicate-wild-ignore-table=db_name.%_session line


After that, validate that the variable is activated (is shown in the output) by running: 


  show slave status \G 


once the filter is activated, slave server will skip all the statements which meet the given pattern. but before doing any change read how MySQL handles replication rules because you can skip important tables if you don't understand the rules.