Primary immune response is response that appears as a result of the first exposure to antigen. On the other side, secondary immune response is the one that occurs when the organism is exposed to the same antigen for the second, third, fourth time. Responding cells of the first immune response are naïve B and T cells (lymphocytes), while responding cells of the secondary immune response are memory T cells. Secondary immune response is much faster (takes shorter time to establish immunity) and amount of antibodies is higher than in primary immune response.