A 32-year-old woman presents with a 3-week history of painless lymphadenopathy in the neck and axillae. On examination, she has firm, rubbery, non-tender lymph nodes. A lymph node biopsy is performed. Histopathology shows sheets of large cells with prominent nucleoli and abundant cytoplasm (Reed-Sternberg cells). Immunohistochemistry reveals CD30+ and CD15+ cells. The pathologist notes that many of these malignant cells are surrounded by apoptotic bodies and dying lymphocytes. Which of the following best explains the mechanism by which these neoplastic cells evade immune destruction despite being surrounded by cytotoxic T lymphocytes?