This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
[{'content': 'Perforin ? \nSelect and explain. \nA. NK cell, B. Cytotoxic T cell, C. Plasma cell, D. Monocyte', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Cytotoxic T cell Cytotoxic T Lymphocyte-Mediated Apoptosis Cytotoxic T lymphocytes (CTLs) recognize foreign antigens presented on the surface of infected host cells. Upon activation, CTLs secrete perforin, a transmembrane pore-forming molecule, which promotes entry of the CTL granule serine proteases called granzymes. Granzymes cleave proteins at aspaate residues and thus activate a variety of cellular caspases. In this way the CTL kills target cells by directly inducing the effector phase of apoptosis.", 'role': 'assistant'}]