Donor's and recipient's antigen presenting cells co-operatively enhance the allo-reactive proliferation of peripheral blood lymphocytes.

Antigen-presenting cells (APC) play important roles in the allo-reactive proliferation of T cells in vitro and in the allo-graft rejection in vivo. This work was aimed at establishing whether a co-operation of any kind occurs between donor's and recipient's APC during allo-reactions, and whether certain cell surface molecules, such as beta 2-microglobulin (beta 2m) and human leucocyte antigens (HLA), are involved in such an interaction. The data herein reported show that the allo-reactive proliferation of peripheral blood lymphocytes (PBL) is markedly intensified by a positive co-operation between donor's and recipient's APC. Such a synergistic co-stimulatory action can be significantly hindered by a monoclonal antibody aimed against beta 2m while being not changed by monoclonal antibodies binding to either HLA-A-B-C or HLA-DR molecules. Hence, our preliminary results indicate that a positive interaction between donor's and recipient's APC may be of importance for allo-graft rejection.