How Does Having Actemra Affect B And T Cells?

does actemra attack the B cell or T cells I am presently taking humira for about 6yrs.my dr.is suggesting to change to acremra. my RA is active . I have taken orencia in the past and it did not help I think it attacks the B cell I might be using the wrong word attack,I know orencia had something to do with B cell. Ialso was on Remicade and got a reaction Hives,weakness,nauseua . I am nervous to change can you help with some info on actemra.