<prompt> Graft Versus host reaction is mediated byMacrophagesT lymphocytesB lymphocytesT lymphocytes and macrophages  <response>: In GVHD, the donated bone marrow or peripheral blood stem cells view the recipients body as foreign. The donated T cells present in the graft, attack the tissues of the transplant recipient after perceiving host tissues as antigenically foreign. There are two forms of GVHD: Acute graft versus host disease aGvHD. Chronic graft versus host disease cGvHD. Ref: Ananthanarayana textbook of Microbiology 9th edition Pgno : 186 