A 28-year-old woman from Chennai presents with progressive bilateral milky-white macules on her face, dorsal hands, and around her mouth over the past 8 months. Wood's lamp examination shows bright blue-white fluorescence of the lesions. Biopsy from the advancing edge shows complete absence of melanocytes at the basal layer with a lymphocytic infiltrate. The pattern marked **D** in the diagram — Non-Segmental Vitiligo with autoimmune melanocyte destruction — is confirmed. Which of the following best describes the primary pathogenic mechanism driving melanocyte loss in this patient?