Modes of Immune Response


        The body is capable of two major types of immune response to an infection;
The production of antibodies, illustrated here on the left, and cell mediated response on the right.

      With antibody production, a B-cell presents antigen to a TH2 cell. This triggers the release of cytokines, including interleukin 4, interleukin 10, and interleukin 13. The B-cell then divides and differentiates into plasma cells producing antibody.

    With cell mediated response, a macrophage internalises material and interacts with a TH1 cell, which causes the production of cytokines, including interferon gamma, by the TH1 cell. This is capable of activating the macrophage and inducing MHC class II molecules on its surface.

    When an antibody response takes place, interleukin 10 cytokines produced by the TH2 cell will prevent TH1 cells from producing interferon gamma, effectively suppressing the cell mediated response.

    If a cell mediated response occurs, the interferon gamma, which activates the macrophage, also prevents the production of cytokines by the TH2 cell, thus suppressing the antibody response. The immune system therefore goes into one mode of response or the other.

     Another layer of activity which effects the type of response which predominates is the production of interleukin 13 cytokines by the TH2 cell in an antibody response. This blocks the production of interleukin 1 and Tumour Necrosis Factor which are the prime effector cytokines of the macrophages. It also promotes B-cell proliferation.

   With the cell mediated response, the production of interleukin 12 by macrophages tends to promote differentiation of T-cells into its pathway, loading up more cells which can reinforce this aspect of the response.