in the first host antigen-presenting cells present alloantigen in association with host ia to host th ( the conventional form of antigen presentation ) , while in the second passenger leucocytes ( dendritic cells ) in the donor allograft present incompatible ia ( class ii ) antigen directly to host th cells , or indeed if ia is identical with the host they may present class i antigen to host th cells .
C0206431
antigen presentation
C0019630
class ii