Simplify the following text for a Grade 9 native English-speaking person.
Original: Effector lymphocytes function to eliminate the antigen , either by releasing antibodies ( in the case of B cells ) , cytotoxic granules ( cytotoxic T cells ) or by signaling to other cells of the immune system ( helper T cells ) .
Simplified: Cytokines signal to other immune cells that there is a foreign antigen present . Other T cells , called cytotoxic T cells , produce toxic granules which cause the death of infected cells .