Asialo GM1+ NK cells have opposite roles in the activation of alloreactive cytotoxic T lymphocyte (CTL) response in vitro and in vivo

The immuno-regulatory role of AsialoGM1+ murine NK cells in the induction of allogeneic cytotoxic T cell responses was studied in vivo and in vitro. Depletion of ASGM1+ cells from the (CBAxC57BL/6)F1 cells used for the foot-pad immunization of CBA mice greatly reduced the formation of allospecific CTLs. However, highly purified ASGM1+ cells were not efficient stimulators of alloCTLs in vivo by themselves. When the same genetic combination was used in alloCTL stimulation culture in vitro, ASGM1+ cells were seen to suppress the activation of the CTL response. The opposite roles of ASGM1+ cells in the alloCTL activation in vivo and in vitro were seen when both lymphoid cells (spleen cells or peripheral blood cells) and non-lymphoid cells (epidermal cells) were used as stimulators. The data presented in this paper suggest that during the alloCTL activation, ASGM1+ cells have an important enhancing role in vivo; but in vitro these cells suppress the antigen-presenting cells.