Which of the following statement(s) is/are CORRECT for antigen activated effector T cells? P. CD4+ cells make contact with macrophages and stimulate their microbicidal activity. Q. CD4+ cells make contact with B cells and stimulate them to differentiate into plasma cells. R. CD8+ cells make contact with B cells and stimulate them to differentiate into plasma cells. S. CD8+ cells make contact with virus infected cells and kill them.