So plasma cells are those cells that produce antibodies while memory B cells store a copy of that antibody in case reinfection ever takes place. Now, instead of the CD four being a helper T cell, let's suppose we have some other type of T lymphocyte that binds to, let's say, a macrophage. In such a case, we can actually stimulate the cell mediated immunity. So CD four T cells can also bind to APts such as macrophages and dendritic cells and they release these chemicals known as lymphocines. And these lymphocines will stimulate our cell mediated immunity. And that means it will call upon other macrophages, other wide blood cells that will come to that infected area and begin our defensive mechanism response engulfing those pathogenic agents.