Regulatory T Cells Increase the Avidity of Primary CD8 + T Cell Responses and Promote Memory

Treg-ulating Immune Responses There are many checks and balances to keep the immune system from running amok. One of the most critical is a specialized population of T cells, called regulatory T cells (T regs ). In their absence, a lethal autoimmune disease develops in both humans and mice. Although T regs are well known for their suppression of autoimmune responses, how they modulate responses to infectious agents is less well understood. Using inducible deletion of T regs in mice, Pace et al. (p. 532 ) showed that T regs are important for shaping the avidity of CD8 + T cell responses. In the absence of T regs , CD8 + T cell responses were of lower avidity, and the CD8 + T cells were more responsive to lower-affinity antigens. When T regs were absent, stable interactions between T cell and antigen-presenting cells were increased as a result of higher amounts of chemokine expression in the lymph nodes. T reg depletion also resulted in a lower-avidity CD8 + T cell response to infection with the bacterial pathogen Listeria monocytogenes .