Mannose-sensitivity and cross-reactivity with YAC-1 cells of cytotoxic T cells against syngeneic tumor cells.

Cytotoxic T lymphocytes (CTL) were raised against syngeneic plasmacytoma MOPC-315 cells by culturing spleen cells immunized with MOPC-315 cells 7 to 14 days previously, either in the presence or absence of MOPC-315 cells. The characteristics of these CTL were investigated in relation to those of natural killer (NK) cells. A portion of the CTL population cross-reacted with NK-sensitive YAC-1 cells. The cytotoxic activity of these CTL was blocked strongly by D-mannose and weakly by alpha-methyl-D-mannoside and glucose, but was not affected by galactose or N-acetyl-D-glucosamine. All of the above compounds blocked the activity of NK, but not that of CTL against allogeneic cells. Thus, these CTL have some similar properties to NK cells, but are clearly distinct from NK cells in the surface phenotype: asialo GM1 is positive in the membrane of NK, but negative in that of CTL. The mannose-sensitivity of the CTL activity was not observed when CTL to MOPC-315 cells were generated during the culture of twice-immunized spleen cells plus MOPC-315 cells. Furthermore, the activity of CTL obtained during the reculture of mannose-sensitive CTL with MOPC-315 cells was not blocked by mannose. These results suggest the existence of a maturation process of the CTL population to syngeneic MOPC-315 cells in terms of the sensitivity to D-mannose.