title: Apoptosis of purified CD4+ T cell subsets is dominated by cytokine deprivation and absence of other cells in new onset diabetic NOD mice.
abstract: BACKGROUND
  Regulatory T cells (Treg) play a significant role in immune homeostasis and self-tolerance. Excessive sensitivity of isolated Treg to apoptosis has been demonstrated in NOD mice and humans suffering of type 1 diabetes, suggesting a possible role in the immune dysfunction that underlies autoimmune insulitis. In this study the sensitivity to apoptosis was measured in T cells from new onset diabetic NOD females, comparing purified subsets to mixed cultures.
  
  
  RESULTS
  Apoptotic cells are short lived in vivo and death occurs primarily during isolation, manipulation and culture. Excessive susceptibility of CD25(+) T cells to spontaneous apoptosis is characteristic of isolated subsets, however disappears when death is measured in mixed splenocyte cultures. In variance, CD25(-) T cells display balanced sensitivity to apoptosis under both conditions. The isolation procedure removes soluble factors, IL-2 playing a significant role in sustaining Treg viability. In addition, pro- and anti-apoptotic signals are transduced by cell-to-cell interactions: CD3 and CD28 protect CD25(+) T cells from apoptosis, and in parallel sensitize naïve effector cells to apoptosis. Treg viability is modulated both by other T cells and other subsets within mixed splenocyte cultures. Variations in sensitivity to apoptosis are often hindered by fast proliferation of viable cells, therefore cycling rates are mandatory to adequate interpretation of cell death assays.
  
  
  CONCLUSIONS
  The sensitivity of purified Treg to apoptosis is dominated by cytokine deprivation and absence of cell-to-cell interactions, and deviate significantly from measurements in mixed populations. Balanced sensitivity of naïve/effector and regulatory T cells to apoptosis in NOD mice argues against the concept that differential susceptibility affects disease evolution and progression.
authors.affiliation: Frankel Laboratory, Schneider Children's Medical Center of Israel, Petach Tikva, Israel.
authors.forename: Ayelet
authors.initials: A
authors.lastname: Kaminitz
authors.forename: Enosh M
authors.initials: EM
authors.lastname: Askenasy
authors.forename: Isaac
authors.initials: I
authors.lastname: Yaniv
authors.forename: Jerry
authors.initials: J
authors.lastname: Stein
authors.forename: Nadir
authors.initials: N
authors.lastname: Askenasy
mesh_terms: D000818:Animals; D017209:Apoptosis; D018106:CD28 Antigens / Q000096:biosynthesis; D017252:CD3 Complex / Q000096:biosynthesis; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology*; D016923:Cell Death; D016207:Cytokines / Q000378:metabolism*; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism; D005260:Female; D006706:Homeostasis; D007376:Interleukin-2 / Q000378:metabolism; D053645:Interleukin-2 Receptor alpha Subunit / Q000096:biosynthesis; D051379:Mice; D008810:Mice, Inbred C57BL; D016688:Mice, Inbred NOD
chemical_list: D018106:CD28 Antigens; D017252:CD3 Complex; D016207:Cytokines; D007376:Interleukin-2; D053645:Interleukin-2 Receptor alpha Subunit