A paragon of self-tolerance: CD25+CD4+regulatory T cells and the control of immune responses

Table 1 Comparison of the phenotype of conventional naïve CD4⁺ T cells and CD4⁺ regulatory cells (T_R)

Conventional naïve helper T cell	Natural regulatory T cell (T_R)
Foxp3 ^-	Foxp3 ⁺
CD5^low, CD11a^low, CD25^low, CD38^low, CD44^low, CD45RB^high, CD54^low, CD103ε^low, GITR^low	CD5^high, CD11a^high, CD25^high, CD38^high, CD44^high, CD45RB^low, CD54^high, CD103^high, GITR^high
About 90–95% of splenic CD4⁺ T cells	About 5–10% of splenic CD4⁺ T cells
Responsive to conventional T cell stimuli	Anergic to conventional T cell stimuli
Non-suppressive	Suppressive

Many of the distinctions are not absolute; for instance, activated non-regulatory effector T cells express cell surface markers with a pattern similar to that of T_R cells, so such discrimination is possible only with constitutive expression. Currently, expression of Foxp3 seems to be the most accurate marker for T_R cells because this does not vary with the activation state.

ISSN: 1478-6362