Now, memory cells are those cells of our body that remain with us for the duration of our lifetime. And they keep a copy of this antigen in case reinfection ever takes place. And if reinfection does take place, they elicit a secondary immune response that is much quicker and more efficient than a primary immune response. Now, what about the T lymphocytes? So this dendritic cell can also interact with T lymphocytes. There are four different types of T lymphocytes.