<prompt> Most important antigen initiating graft rejectionMHC - moleculePolysaccharideDHAHLA - Antigen  <response>: the most important consequence of direct recognition is the activation of CD8 T cells which recognise class I MHC molecules in the graft.Host CD4 helper T cell may be triggered into proliferation and cytokine production by recognition of donorclass II MHC molecules and drive an inflammatory response 