Regulatory CD4(+) CD25(+) T (Treg) cells with the ability to suppress host 
immune responses against self- or non-self antigens play important roles in the 
processes of autoimmunity, transplant rejection, infectious diseases and 
cancers. The proper regulation of CD4(+) CD25(+) Treg cells is thus critical for 
optimal immune responses. Toll-like receptor (TLR)-mediated recognition of 
specific structures of invading pathogens initiates innate as well as adaptive 
immune responses via antigen-presenting cells (APCs). Interestingly, new 
evidence suggests that TLR signalling may directly or indirectly regulate the 
immunosuppressive function of CD4(+) CD25(+) Treg cells in immune responses. TLR 
signalling may shift the balance between CD4(+) T-helper cells and Treg cells, 
and subsequently influence the outcome of the immune response. This 
immunomodulation pathway may therefore have potential applications in the 
treatment of graft rejection, autoimmune diseases, infection diseases and 
cancers.