The cell-mediated response is part of the
immune response against
infection of cells.
T cells are responsible fo this
response. They differentiate under the influence of the
thymus and respond to
bacteria and viruses within infected
body cells, also
cancer cells and
transplanted tissues.
A
macrophage engulfs a bacteria and
antigens are stripped and put on
receptors which are presented on the surface of the macrophage. This antigen is presented to a virgin T cell. The
T cell receptor must recognize botht the
MHC-II protein and the specific antigen fragment to bind.
A
CD4 protein also helps secure the relationship between the macrophage and the T cell.
The T cell becomes
activated and divides into
helper T cells,
cytotoxic T cells.
The helper T cells help activate
B cells in the humoral response.
The T cells also
secrete interleukins, some of which cause a fever or help
differentiation of other T cells.
The cytotoxic T cells are the
effectors of the cell-mediated response. They
search and destroy infected cells by secreteing chemicals that
punches holes in the infected cell's
membrane, causing
lysis.