system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
A 50-year-old man presents to a clinic with a skin lesion on his forearm, which recently changed in color from light brown to brown-black. The lesion was initially pinhead in size but now has grown to the size of a penny. On examination, there is a 3.5 x 2.5 cm irregularly-shaped lesion on his left forearm. A photograph of the lesion is presented. A biopsy of the lesion shows nests of pigmented melanocytes, with few areas showing invasion into the superficial dermis. The physician talks to the patient about a new drug, a monoclonal antibody against the cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) molecule, that has recently been launched in the market for his condition. The CTLA-4 molecule usually interacts with which of the following on the antigen-presenting cells?
assistant
B7