Helper T cells.
   A  protein  (CD4) of a helper T cell binds a MHC surface molecule from
   an infected cell.
   The helper T cells stimulate proliferation of cytotoxic T cells in the
   cell-mediated immunity. Video:  <A ClAsS=MID Href="../../../med/Vid/Campbell8e/43_Animations/43_17HelperTCells_A.swf" oNClick="popurlt('../../../../med/Vid/Campbell8e/43_Animations/43_17HelperTCells_A.swf');txtcolor('helper_t1','gray');return false;" Id=helper_t1><iMg sRc="/images/shockwave.gif" aLt='' boRDer=0></A>