What are the characteristics of T cell exhaustion?

The most notable characteristics of T cell exhaustion include:

• Caused primarily due to excessive and continual stimulation
• Progressive and hierarchical loss of effector and memory function usually within a few weeks
• Sustained high expression of inhibitory markers with multiple markers being expressed
• Low proliferative capacity
• Low telomerase activity 
• Low or no expression of NK cell receptor markers
• Low or no expression of CD57 in humans