Primary Immune Response: New antigens trigger the primary immune response. Only a few B-cells can make antibody needed to bind to new antigen in body. Takes several days for B-cells to be activated, cloned and form plasma cells producing the specific antibodies. Period between infection and onset of antibody production is the latent period. After this period, number of antibodies in blood rises rapidly and then begins to fall. Slow and weak response to first infection - primary immune response. Symptoms of disease are shown during this period. Plasma cells die once infection is over. Memory T and B-cells remain in the blood after infection. Memory T-cells remember the specific antigens. Memory B-cells record specific antibodies needed to bind to antigen. Person is immune after primary immune response. Secondary Immune Response: Second infection produces a secondary immune response. If there is another infection by the same pathogen, the immune system will produce a quicker, stronger response. Memory B-cells are activated and divide into plasma cells that produce right antibodies to antigen. Memory T-cells are activated and divide into correct type of T-cells to kill the cell carrying the antigen. Response is so fast, pathogen destroyed before it reproduces enough to cause symptoms. Individual immune to that disease.