The homeostasis of the immune system depends on the balance between the immune response to an invaded pathogen and the immune tolerance to self antigens. Both central and peripheral tolerances are important mechanisms for the induction and maintenance of T cell tolerance. Recently, much attention has been paid to regulatory T cells （Treg）, which play a significant role in maintaining peripheral immune tolerance. So far, there has been no satisfactory advance regarding the surface markers of Treg cells, as none is unique for Treg cells. In this review, we summarize some important molecules expressed in naturally occurring CD4^＋CD25^＋ Treg cells （nTreg）, including forkhead/winged-helix family transcriptional repressor p3 （Foxp3）, the tumor necrosis factor receptor （TNFR） family, CD28/CTLA4 molecules, chemokine receptors, Toll-like receptors （TLRs）, membrane- bound TGF-β and other molecules, such as neuropilin-1, lymphocyte activation gene-3 （LAG）-3 and granzyme. This review provides a collective view on current studies of nTreg cell activation and development related to the expression of molecules and cell phenotype markers, which is important for elucidation of nTreg cell origin, development and function. Cellular ＆ Molecular Immunology. 2006;3（3）：189-195.
B and T lymphocyte attenuator （BTLA）, identified as an immune inhibitory receptor recently, plays widespread roles on T and B cells. Emerging evidence has generated plentiful information on the mechanisms which BTLA mediates negative regulation in immune responses and involves in a variety of physiological and pathological processes. The exploration of the biological mechanisms and regulation of BTLA will open possibilities on novel therapeutic strategies in immune-related diseases. Cellular ＆ Molecular Immunology. 2005;2（6）：427-432.
