Please be advised that a J-1 holder is only allowed to perform the activity listed on his/her Form DS-2019 and as stated in the regulations for that category of exchange. It will also identify the start and end date of the exchange program.
Issuance of the J-1 visa, like all non-immigrant visas, is at the discretion of Consular Officers viewing visa applications at U.S. embassies and consulates. This means that even if you are accepted to an exchange visitor program and have received your DS-2019, the Consular Officers decide if you receive the J-1 visa.