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': 'Which of the following white blood cells act as scavengers when they engulf and digest pathogens? \nSelect and explain. \nA. Macrophages, B. T cells, C. B cells, D. Lymphocytes', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Macrophages are a type of white blood cell,\xa0of the immune system,\xa0that engulfs and digests cellular debris, foreign substances, microbes,\xa0cancer cells, and anything else that does not have the type of proteins specific to healthy body cells on its surface\xa0in a process called phagocytosis.\nThis large phagocytes are found in essentially all tissues,\xa0where they patrol for potential pathogens\xa0by amoeboid movement.\xa0They take various forms (with various names) throughout the body (e.g., histiocytes, Kupffer cells, alveolar macrophages, microglia,\xa0and others), but all are part of the mononuclear phagocyte system.\xa0Besides phagocytosis, they play a critical role in nonspecific defence (innate immunity) and also help initiate specific defence mechanisms (adaptive immunity) by recruiting other immune cells such as lymphocytes.\xa0For example, they are important as antigen presenters\xa0to T cells.\xa0In humans, dysfunctional macrophages cause severe diseases such as a chronic granulomatous disease\xa0that result in frequent infections.', 'role': 'assistant'}]