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
CD 4 are associated with - 
Select and explain. 
A. Helper T cell, B. Supressor T cell, C. NK cells, D. T cell antigen receptor complex
A: Helper T cell
Answer: A: Helper T cell 
Explanation: T cells can differentiate into effector cells. Helper (CD4) T-cell activity, in addition to stimulating B cells to produce antibodies, promotes the development of delayed hypersensitivity and thereby also serves in the defense against intracellular agents, including intracellular bacteria (eg, mycobacteria), fungi, protozoa, and viruses. Reff: Ananthanarayanan & Panikers textbook of microbiology 9th edition pg: 135