Answer
The function of cells of the immune system is to defend the body against potentially dangerous organisms and substances.T-cells and B-cells have to learn to recognize specific molecules on potentially harmful entities (antigens, and pathogens); They then develop the ability to produce molecules (antibodies) that will inactivate or destroy the non-self entities. Naive B cells are B cells that have never met their antigen. When the naive B cell meets its antigen for the first time, it takes some time to identify it and slowly produces molecules that have the function of destroying or inactivating the antigen or organism--this is lag time.. In the case of B cells the transformed cells that elaborate the antibodies are called plasma cells This set of responses of an immune cells to their specific antigen for the first time is appropriately called a primary immune response,
A primary immune response is slow, and the titer of antibodies it produces is relatively low-- compared with that produced by memory cells in secondary immune responses.
Immune cells that have learned to identify their specific antigen and to produce antibodies to inactivate it are called memory cells. The memory they retained from the initial contact with their antigen, enable cells of that clone to respond very quickly on subsequent encounters with that specific antigen, These subsequent contacts --after the first--result in quicker more vigorous immune responses of the memory cells. This is the secondary response.
Not only is the secondary response quicker, many more antibodies are produced, and the high titer is maintained longer. In addition, immunity is established faster, and may be functional for many months , even for many years,
Work Step by Step
When naive B cells or T cells meet their specific antigen for the first time they learn to recognize their antigen and to produce antibodies against it. This is a slow process that may take anything from one to two weeks. .The antibody titer rises slowly, relatively few antibodies are made, and effective immunity comes into existence after many days-- or weeks..
Some of the cells initiated in the primary responses form clones of antibody secreting plasma cells. These plasma secrete mainly IgM antibodies, and smaller amounts of IgG.
Initiated memory cells react more quickly on subsequent contacts with their specific antigen. Antibody titers rise to high levels within a few days (3-6 days) . In the secondary response not only are many more antibody molecules produced , but lag time is shorter, effective immunity is established in a shorter time, and lasts for months and years --even for a lifetime in some cases..
Memory cells produce mainly IgG antibodies, but also some IgM , and IgA molecules. IgE antbodies are produced in allergic and parasitic diseases.
