This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunity, Subject name: Pathology
Role of macrophages in antibody production is? 
Select and explain. 
A. Antigen presentation, B. B cell production, C. Class switching, D. B cell activation
A: Antigen presentation
Answer: A: Antigen presentation 
Explanation: Ans. (a.) Antigen presentation(Ref: Robbins 9th/198)Macrophages that have phagocytosed microbes and protein antigens process the antigens and present peptide fragments to T cells. Upon activation, B lymphocytes proliferate and then differentiate into plasma cells that secrete different classes of antibodies with distinct functions