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
Those cells that must co-operate with B cells to produce antibody in response to ceain antigens are known as 
Select and explain. 
A. Stem cells, B. Plasma cells, C. Macrophages, D. Helper T cells
D: Helper T cells
Answer: D: Helper T cells 
Explanation: In the antibody-mediated immune response, CD4 T lymphocytes recognize the pathogen's antigens bound to the class II MHC molecules on the surface of an antigen-presenting cell (APC) (eg, macrophage, B cell), and as a consequence of this interaction, cytokines are produced that stimulate B cells to express antibodies that display specificity for the antigen. Stem cells - Pleuripotent cells Plasma cells - Antibody production Macrophages - Phagocytosis Ref : Ananthanarayana textbook of Microbiology 9th edition Pgno : 135