T-cell system

The immime system is characterised by an ability to distinguish between self and non-self. Exogenous materials are consistently bracketed as non-self but also endogenous entities, if recovered outside their principal habitat, can be immuno active. The immunological response originates from either of two different systems, B-cells or T-cells, where the B-cell system handles non-cellular intruders and the T-cell system is dedicated to whole cells. 

As parent metal alters sodium balance and lipid metabolism it induces metallothionein synthesis. Nickel chloride affects the T-cell system and suppresses the activity of natural killer cells. If given orally or by inhalation, nickel chloride has been reported to decrease iodine uptake by the thyroid gland. 

By September 1981, the Center for Disease Control (CDC) in Atlanta had compiled a list of just over 100 deaths ascribed to Kaposi s sarcoma or to Pneumocystis carinii pneumonia or both. Ninety-five of these patients were gay white males. The number of such deaths rose to 270 by the end of the year, and all of the post-mortems revealed immune systems that were essentially devoid of T-lymphocytes with body organs engulfed by organisms like Staphylococcus aureus, E.coli and Cryptosporidium. Somewhat surprisingly, the numbers of B-lymphocytes, that is, the ones already committed to producing antibodies, were within normal levels, and so the disease was clearly highly specific for the T cell system. In particular, one class of lymphocyte, the CD4 lymphocyte, was absent or very severely diminished in numbers. 

This review has focused on effects of protein energy malnutrition on immune responses in the human host. These studies document major impairment of the T-cell and complement systems in severe PEM, and less profound, but probably significant, effects upon B-cells and immunoglobulins, particularly SIgA. While mild-moderate malnutrition also alters the T-cell system and may predispose to... 

Thus a plethora of classical T cell markers, T cell specific cytokines and transcription factors have been reported to date in several species, suggesting that the fish T cell system has many characteristics in common with its mammalian counterparts. However, the presence of additional molecules (e.g. CD4L, IFN-yrel) and putative common ancestors (e.g. IL-17C/E,CD25 like) clearly show that fish T cell markers and T cell functions are likely to be different relative to mammals, and even the number and types of T cell subsets will potentially vary. 

In addition to their endocrine disrupting properties, it must be appreciated that many of the chemicals in question possess more general toxic properties, which may be potentiated by metabolism by the organism. Several PAHs, PCBs and PCDDs are carcinogenic, while certain phthalate esters can enhance the excretion of zinc, potentially leading to zinc deficiency. Zinc, an essential element, plays a vital role in spermatogenesis and mature T-cell production. Deficiency may result in abnormalities of the male reproductive system, depletion of spermatogenesis and suppression of the immune system. 

In addition to antibodies, the immune system also consists of bone-marrow derived lymphocytes, or B cells, and T cells that come from the thymus gland, both of which (indirectly) produce antibodies. These cells, in turn, may be helped by helper cells (= H) and suppressed by suppressor cells (= S). Helper cells may be alarmed as to the presence of antigens by macrophages (= M) that eat the antigens and leave parts of their meal on their cell surface. 

Stauffer [stauff92] reports that the concentration of cells in this system quickly saturates. For low initial concentrations po, the viral population wins over the population of cells of the immune system and the system can be said to develop Aids. For larger po, the population of helper T cells becomes greater than that of the virus and the immune system wins. 

Cytokines. Figure 1 Inhibition of cytokine synthesis during activation of the specific immune system. The monoclonal antibodies Muromonab and Basiliximab are specific for the CD3 complex of the T-cell receptor, and for the IL-2 receptor on lymphocytes, respectively. Cyclosporin and Tacrolimus inhibit activation of cytoplasmic NF-AT, a transcription factor essential for activation of the IL-2 gene ( NFAT Family of Transcription Factors). Sirolimus interferes with mTOR signaling and inhibits IL-2 dependent proliferation. Red pharmaka, blue target proteins. 

The field of DNA vaccination started when eukaryotic expression vectors were injected into the muscle of laboratory animals [2]. The authors observed protein expression for more than 2 months after injection and noted that no special delivery system was required to obtain this expression. Subsequently, it was demonstrated that antibodies can be induced simply by injecting plasmid DNA into the muscle of mice [3]. Subsequent studies found that the injection of expression plasmids also leads to the induction of a cytotoxic T-cell response. After injection, the DNA enters cells of the vaccinated host and the encoded gene becomes expressed. This eventually leads to the induction of a cellular cytotoxic T-cell, T-helper, and/or humoral (antibody) immune response. 

Cole et al. (1995) reported on knock-out mice with a germ line deletion of GR. They demonstrated that lack of GR leads to perinatal death, atelectasis of the lung, and lack of adrenalin synthesis. To circumvent perinatal lethality, Tranche et al. (1999) and Brewer et al. (2003) generated tissue-specific somatic deletions of GR. This allowed to characterize GR function in the CNS, the immune system, and the liver in more detail. In particular, these approaches revealed novel aspects of organ-specific glucocorticoid physiology such as anxiety-like behavior, growth control, and polyclonal T cell activation. 

Large granular lymphocytes, not belonging to either the T- or B-cell lineage. Natural killer (NK) cells are considered part of the innate defense system since, in contrast to cytotoxic T-cells, they are able to kill certain tumor cells in vitro without prior sensitization. The basal activity of NIC cells increases dramatically following stimulation with type I IFNs. In addition, NK cells display Fc-receptors for IgG and are important mediators of Antibody-Dependent-Cell-mediated-Cytotoxicity (ADCC). 

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