Figure 2. Mouse models for studying memory T_Reg cells.

Three primary mouse models have been used to identify and to characterize memory regulatory T (T_Reg) cells. a. In a tissue-specific inducible antigen model, expression of a pseudo-self antigen can be precisely turned on and off. This system facilitates the generation of memory T_Reg cells (by turning on the antigen) and their isolation and characterization in both secondary lymphoid organs and peripheral tissues after the antigen is turned off^11,13. b. In an antigen-specific gestational model, maternal CD4⁺ T cells with surrogate fetal specificity can be precisely identified during primary pregnancy, post-partum and with fetal antigen restimulation in subsequent pregnancies¹². c. In an acute infection model with influenza virus, the initial infection is rapidly cleared but virus-specific memory T_Reg cells are generated and maintained long term. These memory T_Reg cells mitigate the tissue damage that occurs upon reinfection with the virus^14,15.