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
Leukotrienes are secreted by all except - 
Select and explain. 
A. Macrophages, B. T4 cells, C. T8 cells, D. Platelets
D: Platelets
Answer: D: Platelets 
Explanation: Leukotrienes are a family of eicosanoid inflammatory mediators produced in leukocytes by the oxidation of arachidonic acid and the essential fatty acid eicosapentanoic acid by the enzyme arachidonate 5-lipoxygenase. As their name implies, leukotrienes were first discovered in leukocytes, but have since been found in other immune cells like macrophages Reff: www.medscape.com