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
.
