Immune-mediated destruction of melanocytes in halo nevi is associated with the local expansion of a limited number of T cell clones.

The beta-chain repertoire of the T cells that infiltrate spontaneously regressing nevi (the halo nevus phenomenon) was studied. In addition to the infiltration of the halo nevi by cutaneous lymphocyte-associated Ag-positive lymphocytes, oligoclonal expansion of T cells was observed in all halo nevi of all patients. T cells using the same TCR beta-chain were observed in distinct halo nevi of the same patient but not in his peripheral blood, demonstrating a local expansion of common clones that are most likely activated by the Ag(s) shared by independent halo nevi of the same patient.