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: Microbiology
The key cell types involved in the acquired immunity include all EXCEPT: 
Select and explain. 
A. B lymphocytes, B. Erythrocytes, C. T lymphocytes, D. Antigen presenting cells (APC)
B: Erythrocytes
Answer: B: Erythrocytes 
Explanation: The main physiological role of red blood cells (RBCs), or erythrocytes is to transport gases (O2, CO2) from the lung to the tissues and to maintain systemic acid/base equilibria. 
In addition, RBCs are well equipped with antioxidant systems, which essentially contribute to their function and integrity.
They are not involved in acquired immunity.