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: Unknown
Type I helper cells secrete: 
Select and explain. 
A. Interleukin-l, B. Interleukin-2, C. Interleukin-4, D. Interleukin-5
B: Interleukin-2
Answer: B: Interleukin-2 
Explanation: IL -2 
• Interleukins are “cytokines”.
• Proteins of usually low molecular weight.
• Regulating important biological processes.
• Interleukins are produced by Monocytes, Macrophages, B and T Lymphocytes, mast cells, neutrophils. 
IL1 causes fever
IL2 T cell stimulation
IL3 Bone Marrow stimulation
IL4 IgE Stimulation
IL5 IgA Stimulation