Self-antigens, immune response

T-Lymphocytes (4,5) and other cellular components of the immune system also have equally wide implications in regulation of the normal immune system. The T-lymphocytes play a central role in the body s response to harmful antigens and tumor—host interaction (4). Responses involve antigens derived from vimses, bacteria, parasites, and tumors. T-ceUs also participate in the immune surveillance response, where self-antigens are recognized, but usually sequestered within the cell and, when exposed, become markers of cellular damage. 

Transformed cells expressing tumour-specific surface antigens that closely resemble normal surface antigens may not induce an immune response. Furthermore, some tumour antigens, although not usually expressed in adults, were expressed previously during the neonatal period (i.e. just after birth) and are thus believed by the immune cells to be self . 

In summary, although numerous AhR-dependent changes in the bone marrow and thymus have been found in TCDD-treated mice, it appears that these effects are self-limiting in adult mice, as T and B cell numbers are not reduced in secondary lymphoid tissue except after exposure to high doses of TCDD or in the context of an adaptive immune response. More subtle effects, such as changes in the antigenic specificity of peripheral T and B lymphocyte populations, have not been documented. 

The mechanism most commonly invoked to explain the association of infection with autoimmune disease is molecular mimicry that is, the concept that antigens (or more properly, epitopes) of the microorganism closely resemble self-antigens.50 The induction of an immune response to the microbial antigen thus results in cross-reactivity with selfantigens and the induction of autoimmunity. Although epitope specific cross-reactivity has been shown in some animal models,48,51 53 molecular mimicry is clearly demonstrated to be the causative mechanism in few, if any, human diseases.3 54,55... 

Regulatory T (T ) cells represent a distinct T-cell lineage that plays a key role in tolerance to self antigen and prevention of autoimmune diseases, as well as in inappropriate immune responses involved in allergic diseases [1-3]. Tr cells are characterized by a set of phenotypic and functional... 

The hypothesis of the existence of T cells that specifically regulate immune responses towards self and allogeneic antigens has been formulated since 25 years ago [21]. However, phenotype and functional properties of Treg have been at least partially defined only in the last few years. 

Finally, besides conventional liposomes that are made from natural (e.g., egg yolk and soybean) or synthetic phospholipids, novel liposomes called archaeosomes that are prepared from the polar ether lipids extracted from various archaeobacteria proved also interesting for the design of vaccines as peptide antigen carriers (71) and as powerful self-adjuvanting vaccine delivery vesicles that promote both humoral and cell-mediated immunity (72). Related to this, one can mention that pseudopeptides, which are less prone to proteolysis when conjugated to liposomes, were also competent in triggering a humoral immune response (73). 

In addition to having an overabundance of several self-antigens, tumor cells express unique antigens, which can be recognized by the host immune system, provided that the immune system is simultaneously activated. Without this activation, the immune system will become tolerized to the unique antigens known as tumor-associated antigens (TAAs), which are usually small peptides of 8 to 10 amino acids. The potential exists for the eradication of cancers by injection of TAAs and the subsequent immune response. Indeed, there have been many tumor-reactive CTLs identified that recognize specific TAAs (15). 

After an antigen (a non-self molecular entity) has entered the body, it is recognized by the cells of the immune system. An important step in eliciting an efficient immune response to an... 

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