Antigens Treg cells

Autoimmune Disease. Figure 1 Mechanisms of self tolerance. DC, dendritic (antigen presenting) cell T, T-lymphocyte Th, T helper lymphocyte Treg, T regulatory lymphocyte. For details see text. 

Although closely related, monocytes/macrophages (MO) possess features that are distinct from DCs. Due to their limited expression of T-cell costimulatory molecules, MO are not able to prime T cells de novo, but rather stimulate effector/memory T cells by the secretion of cytokines, which support T-cell proliferation. As DCs, MO differentiate from myeloid precursors and form a heterogeneous population of antigen-presenting cells (APCs) that link the innate and adaptive immune systems. However, their ability to interact with T cells via MHC class II TCR interaction(s) as well as engagement of T-cell costimulatory receptors on their surface, makes close contact between MO and Tregs likely to occur in vivo. 

Treg cells not only prevent undesired immune responses to innocuous antigens applied onto the skin, but also promote the termination of ongoing... 

Double negative (CD4-CD8-) TCR-ap-f Treg cells that mediate tolerance in several experimental autoimmune diseases have been described [ 111 ]. These double negative T cells are specific for MHC class I molecules and the suppressive effect of these cells on the proliferation and cytotoxic activity of CD8-I- T cells with the same antigen specificity was not mediated by cytokines, but instead was attributed to Fas-mediated apoptosis of alloreactive T cells [112]. 

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