Cytokine profile of draining lymph node lymphocytes in mice grafted with syngeneic keratinocytes expressing human papillomavirus type 16 E7 protein

Studies on the immune response to human papillomaviruses are compromised by the extreme host and tissue specificity of these viruses. To circumvent this, a mouse model system has been used in which antigen is presented via a differentiated, syngeneic keratinocyte graft expressing human papillomavirus type 16 (HPV-16) E7 protein. Using this model, previous studies have shown that animals grafted with a high cell inoculum (1×107 NEK 16 cells) exhibit a delayed-type hypersensitivity response that is E7-specific and CD4+-mediated, but those receiving a low cell inoculum (5×105 NEK 16 cells) are rendered unresponsive to subsequent and repeated antigen challenge. To investigate the mechanisms underlying this phenomenon, we have analysed the early changes in the cytokine profile of the graft-draining lymph node (GDLN) after high- or low-dose grafts. At 4 days post-grafting, there was a peak secretion of IL-2 associated with a decreased secretion of IL-4 by γδ-TCR+ cells in the group receiving 1×107 NEK 16 cells. At 5 days post-grafting, there was a peak secretion of IL-10 by CD8+ cells in both the high- and low-dose graft groups compared with controls. In contrast, low dose-grafted animals showed an increase in IL-4 production by CD8+ cells at this time-point. Low antigen challenge in this model system is associated with the appearance of a CD8+ population in the GDLN that secretes both IL-4 and IL-10. This population may represent a Tc2 or Ts subset that could induce further unresponsiveness.