Antigen presentation stimulates T cells to become either "cytotoxic" CD8+ cells or "helper" CD4+ cells. Cytotoxic cells directly attack other cells carrying certain foreign or abnormal molecules on their surfaces. Helper T cells, or Th cells, coordinate immune responses by communicating with other cells. In most cases, T cells only recognize an antigen if it is carried on the surface of a cell by one of the body’s own MHC, or major histocompatibility complex, molecules.
<a href="//commons.wikimedia.org/wiki/User:Fred_the_Oyster" title="User:Fred the Oyster">Fred the Oyster</a>
2014-10-20
<a href="//commons.wikimedia.org/wiki/File:Antigen_presentation.jpg" class="image"><img alt="Antigen presentation.jpg" src="https://upload.wikimedia.org/wikipedia/commons/thumb/9/98/Antigen_presentation.jpg/100px-Antigen_presentation.jpg" decoding="async" width="100" height="89" srcset="https://upload.wikimedia.org/wikipedia/commons/thumb/9/98/Antigen_presentation.jpg/150px-Antigen_presentation.jpg 1.5x, https://upload.wikimedia.org/wikipedia/commons/thumb/9/98/Antigen_presentation.jpg/200px-Antigen_presentation.jpg 2x" data-file-width="500" data-file-height="447"></a><br><a rel="nofollow" class="external text" href="http://www.niaid.nih.gov/publications/immune/the_immune_system.pdf">The Immune System (pdf)</a>