Question 4 of 6 Intermediate Concept

What is the difference between central and effector memory T cells?

Short answer

Central memory T cells generally express lymphoid-homing molecules such as CCR7 and are primed for recall expansion. Effector memory cells often lack CCR7, circulate through or enter peripheral tissues and can provide faster immediate effector responses. Marker definitions are context-dependent.

Why

T-cell memory is heterogeneous rather than a single developmental endpoint. In a common human peripheral-blood scheme, CD45RA-negative CCR7-positive T cells are called central memory, while CD45RA-negative CCR7-negative cells are called effector memory. Central memory cells more readily traffic to secondary lymphoid tissues and typically support proliferative recall potential.

Effector memory subsets can show more immediate effector functions and differing tissue migration profiles. CD45RA-positive CCR7-negative TEMRA cells and tissue-resident memory cells further complicate the simple two-way split. Imagine profiling vaccine responses.

A rise in CCR7-positive memory-like cells and a rise in cytotoxic CCR7-negative cells may reflect different functions even if both show prior antigen experience. Interpret phenotypes alongside CD62L, CD27, CD28, functional assays, tissue source and CD4 or CD8 lineage. Expression of two markers does not establish long-term persistence or protective immunity on its own.

Common mistakes

Treating CCR7 staining alone as proof of memory function or equating effector memory with terminal exhaustion

The interviewer might ask next

What additional markers and functional tests would you add to separate naïve, TCM, TEM and TEMRA cells?