Table 2.

Activation and differentiation markers used for the study of T-cell responses after natural and vaccine challenges.

Molecule	Function	T-Cell Subset Marker
HLA-DR	Class II major histocompatibility complex molecule	Effector cells
CD38	ADP-ribosyl cyclase ectoenzyme	Effector cells
Ki-67	Nuclear protein expressed during active phases of cell cycle and associated with cell proliferative activity	Effector cells
B-cell lymphoma (Bcl)-2	Anti-apoptotic protein that prevents the release of cytochrome C and oxygen reactive species from mitochondria	Naïve and central memory cells
CCR7	Chemokine receptor for the CCL19 and CCL21 chemokines. Involved in the homing of T-cells to secondary lymphoid organs	Naïve and central memory cells
CD45RA	Phosphatase involved in T-cell receptor signal transduction	Naïve and central memory cells and terminally-differentiated cells
CD45RO	Phosphatase involved in T-cell receptor signal transduction	Memory cells
CD28	Receptor for costimulatory molecules, involved in the amplificationof T-cell receptor signalir	Naïve and memory cells, decreasing cell differentiation
CD127	Alpha chain of the II-7-receptor; IL-7 supports the survival of mature T-cells	Naïve and memory cells, decreasing along cell differentiation
Programmed death 1 protein (PD-1)	Regulatory receptor that inhibits T-cell receptor signaling	Memory cells
Perforin/Granzyme B	Cytotoxic molecules induce apoptosis intarget cells	Effector cells