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
Interleukin secreted by macrophages, stimulating lymphocytes is 
Select and explain. 
A. IFN alpha, B. TNF alpha, C. IL-1, D. IL-6
C: IL-1
Answer: C: IL-1 
Explanation: IL1> IL6

Macrophages release IL – 1 which stimulates the T – helper cells.
The T – cells in response proliferate and release IL – 2 which in turn further stimulates T – cell proliferation and B cell proliferation and differentiation into plasma cells.
Please note that even IL-6 (produced by macrophages) acts on late stages of B cell differentiation enhancing antibody formation. Still, IL-1 being the most important cytokine having systemic effects of inflammation has been chosen as the answer here in preference to IL-6.