Human immune system

Human Immunodeficiency Virus. Human immunodeficiency vims (HIV) causes Acquired Immunodeficiency Syndrome (AIDS), which has no cure. HIV infects the cells of the human immune system, such as T-lymphocytes, monocytes, and macrophages. After a long period of latency and persistent infection, it results in the progressive decline of the immune system, and leads to full-blown AIDS, resulting in death. 

Immunotoxicity. Limited information is available regarding the effects of endosulfan on the human immune system. However, specially designed studies using rats indicate that both humoral and cellular immune responses are depressed by ingested endosulfan at doses that do not induce any overt signs of toxicity (Banerjee and Hussain 1986,1987). In vitro studies support the possibility that endosulfan affects immune system function (Das et al. 1988). These results demonstrate that immunotoxicity may be a more sensitive end point of endosulfan-induced toxicity than other end points, and humans may be at risk for adverse immune effects following exposure to endosulfan. An intermediate-duration oral MRL was derived based on the observation of depressed immune responses (Banerjee and Hussain 1987). 

The Liskamp group also examined the ability of peptoid-peptide hybrids to be bound by the MHC Class II receptor, an important component of the human immune system [39]. Two of three peptoid substitutions in the 14-residue peptide caused substantial decreases in binding affinity, despite the fact that these were solvent-exposed residues. These results were attributed to a loss of hydrogen-bond contacts as well as to steric clashes caused by unfavorable positioning of the new side chain groups. 

The production of N-formylated proteins is a characteristic specific to bacteria and, therefore, an obvious target for the human immune system. It has been shown that professional phagocytes, the first line of defence against invading microorganisms, express receptors that recognise N-formylated peptides [12], and that activation of these receptors mediates migration of... 

A new industrial chlorine alternative was purposefully designed to imitate the stabilized bromine antimicrobials produced naturally in the human immune system. It is the first biomimetic industrial biocide. It is chemically analogous to the antimicrobial product of... 

Human immune system Variable region of antibodies, histocompatibility genes... 

As a bacterial protein, streptokinase is viewed by the human immune system as an antigenic substance. In some cases, its administration has elicited allergic responses that have ranged from mild rashes to more serious anaphylactic shock (an extreme and generalized allergic response characterized by swelling, constriction of the bronchioles, circulatory collapse and heart failure). 

Holladay, S.D. and Smialowicz, R.J., Development of the murine and human immune system differential effects of immunotoxicants depend on time of exposure, Environ. Health Perspect., 108, 463, 2000. 

Immunotoxicity testing in rodents exposed to industrial and/or environmental chemicals, has been recognized as an important toxicological concern for over 25 years. Early immunotoxicity testing relied primarily on the mouse, due to the plethora of immune structure and function research performed by immunologists to better understand the human immune system. As such, the mouse has been the most employed rodent for immunotoxicity testing. Immune system function assays employed in screening for immunotoxicity were developed in adult mice. These same immune function assays have served to help identify toxicant induced immunosuppression in the rat. 

West, L.J. Defining critical windows in the development of the human immune system, Human Experimental Toxicology 21, 499,2002. 

An autoimmune response is rarely detected during preclinical drug development because of the lack of good predictive animal models for the human immune system. Owing to their low incidence and idiosyncratic nature, autoimmune diseases quite often appear as a serious issue only after product launch [2,22]. 

Recently, it has been possible to grow cells of the human immune system in special mice. These mice carry a genetic defect called severe combined immunodeficiency (SCID), which leaves them with crippled immune systems, much like those in AIDS patients. Because SCID mice lack functional cellular immunity, it is possible to implant them with human cells without tissue rejection taking place. Researchers have recently developed techniques to implant human fetal tissues containing stem cells for the blood into SCID mice. It is then possible to reconstitute these mice with functional human immune system cells, including T lymphocytes and B lymphocytes. They have also found that if these SCID mice are infected by HIV, the virus will establish infection in the human tissue and destroy the T helper lymphocytes, just as it does in humans. Thus, it may be possible to study some of the mechanisms by which HIV attacks the immune system in these mice. In addition, they may be very useful for testing potential antiviral drugs. 

Describe how the human immune system works, focusing on the B and T cells. 

Given this structural similarity, it should not be surprising to learn that sulfanilamide competes with p-aminobenzoic acid for a binding site on the surface of dihydropteroate synthetase. Put another way, sulfanilamide binds to the enzyme where p-aminobenzoic acid should bind but no reaction occurs. The consequence is that a step in folic acid biosynthesis is disrupted and the bacterial cell is deprived of adequate folic acid. Nucleic acid synthesis, among other things, is disrupted, leading to a cessation of cell growth and division. The human immune system can mop up what remains. No similar consequences befall the human host since it cannot make folic acid in the first place and must get an adequate supply of this vitamin in the diet. 

Immunotoxicity. There are currently no data on the effects of 2-hexanone on the human immune system via any route of exposure. Animal data included an inhalation study in which there was a 40% decrease in peripheral white blood cells in rats exposed to 2-hexanone (Katz et al. 1980). In addition, 2,5-hexanedione, a metabolite of 2-hexanone, was shown to adversely affect lymphoid organs of the immune system in rats and to cause impairment of immunity in mice (Upreti and Shanker 1987). Immunological assessments, including analysis of peripheral blood components and effects on lymphoid tissue, conducted as part of intermediate-or chronic-duration studies and skin sensitization tests would be useful in developing a dose-response relationship and assessing the potential risk to chronically exposed persons in the vicinity of hazardous waste sites or to exposed workers. 

There was a problem with using mouse monoclonal antibody proteins to treat some human diseases, however. The human immune system recognizes the mouse antibody as the foreign protein it is. 

The effects of interferons on the human immune system are highly variable. IFN-p tends to suppress certain aspects of immune function, whereas IFN-a can inhibit immune cell proliferation IFN-y, on the other hand, displays immune-enhancing properties. All three types of interferon have been studied preclinically and even clinically. 

Any material proposed for implantation, whether for cell transplantation or some other application, must be biocompatible i.e. it must not provoke an adverse response from the host s immune system. If this goal is not met the implant may be rejected. To this end it is important that the material be easily sterilized either by exposure to high temperatures, ethylene oxide vapor, or gamma radiation. A suitable material must therefore remain unaffected by one of these three techniques. However, biocompatibility is not simply a question of sterility. The chemistry, structure, and physical form of a material are all important factors which determine its biocompatibility. Although our understanding of the human immune system is advancing rapidly, it is not yet possible to predict the immune response to a new material. This can only be determined by in vivo experiments. 

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