Q: In this task, you are given a sentence. You are expected to recognize the name of gene or protein. Although there might be several correct answers, you need to write one of them.
 To directly examine the effect of 1 , 25 - ( OH ) 2D3 on T cell activation in the absence of other complicating interactions , we utilized a panel of cloned Ia - restricted T cell hybridomas that secrete IL 2 on activation by cloned Ia - bearing stimulator cells ( TA3 ) or when stimulated by mitogen .
A:
IL 2