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
Memory T cells can be identified by using the following marker? 
Select and explain. 
A. CD45 RA, B. CD45 RB, C. CD45 RC, D. CD45 RO
D: CD45 RO
Answer: D: CD45 RO 
Explanation: Stem memory TSCM cells, like naive cells, are CD45RO-, CCR7+, CD45RA+, CD62L+ (L-selectin), CD27+, CD28+ and IL-7Ra+, but they also express large amounts of CD95, IL-2Rb, CXCR3, and LFA-1, and show numerous functional attributes distinctive of memory cells Reff: www.mayoclinic.com