This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology, Subject name: Microbiology
[{'content': 'True about cytokines is - \nSelect and explain. \nA. It is always a polypeptide, B. It acts on protein targets, C. It takes pa in intrinsic enzymatic reactions, D. Chemotactic', 'role': 'user'}, {'content': 'Answer: A \nExplanation: They are a broad and loose category of small proteins (~5-20 kDa) that are impoant in cell signaling. They act on receptors Ref: Ananathanarayanan & Panikers textbook of microbiology 9th edition pg: 152', 'role': 'assistant'}]