THE IMMUNE-RESPONSE IN HALO NEVI

The mechanism(s) responsible for halo nevus presents a provocative lin k with the immune response to melanoma. Although no direct demonstrati on of melanocyte killing has been observed by the immune effector cell s found within the halo, the abundance of antigen-presenting cells in the regressing nevus and the presence of T lymphocytes at the site of depigmentation suggest that these cells participate in the halo phenom enon. Within the latter population of cells, evidence points to the in volvement of CD8(+) T cells as potential effecters in the destruction of nevomelanocytes. The break in tolerance that triggers migration and the presumed activation of these and other lymphocytes in the nevus i n the apparent absence of disease remains unexplained. This brief over view reviews the evidence for the participation of the immune response in the genesis of the halo nevus.