Immune system hypersensitivity

Not all antigen-antibody reactions are of benefit to the body, as sometimes the complexes (or their subsequent interaction with body tissues) may result in tissue damage. This must be regarded as a malfunction of the immune system and is known as a hypersensitive reaction. These reactions can be categorized into five main types. The first three involve the interaction between antigen and humoral antibody, and as the onset of the reaction is rapid, the condition is termed immediate hypersensitivity. The fourth type (delayed hypersensitivity) involves T cells and the symptoms of the reaction appear after 24 hours. The fifth type is where antibody stimulates cell function. 

A limited study in animals also presents evidence for increased susceptibility to Streptococcus zooepidomicus (Aran d et al. 1986). Immune system effects observed in mice exposed orally to trichloroethylene included inhibition of cell-mediated immunity, delayed type hypersensitivity, and inhibition of antibody-mediated immunity (Sanders et al. 1982). Female mice appeared to be more sensitive than male mice. A study in which a susceptible strain of mice was treated with intraperitoneal injections of trichloroethylene suggests that trichloroethylene can accelerate the autoimmune response (Khan et al. 1995). The immune system may be a sensitive end point for toxic effects from low-level exposure to trichloroethylene however, no firm conclusions can be drawn from the available information. Additional human and animal studies are needed to better characterize this end point and determine the potential for immunological effects for people exposed to trichloroethylene at hazardous waste sites. 

IBS activity may be affected by the immune system. Some IBS patients have been found to have antibodies, which may indicate food hypersensitivity that might be involved in symptom production.14 Specifically, sensitivity has been demonstrated to common foods such as wheat, beef, pork, soy, and eggs. 

This chapter presents specific information with regard to the effects of environmental and occupational exposure to arsenic on inflammatory processes, the immune system, and host defense. While the focus is on the in vivo and in vitro effects of arsenic on host immune responses (e.g., immunotoxicity and hypersensitivity) and their relationship to clinically observed manifestations of arsenic toxicity (e.g., inflammation and skin cancer), information on the potential mechanisms through which arsenic may exert its biological effects is also provided. 

Autoimmunity. In autoimmunity, as with hypersensitivity, the immune system is stimulated by specific responses that are pathogenic, and both tend to have a genetic component that predisposes some individuals more than others. However, as is the case with hypersensitivity, the adverse immune response of drug-induced autoimmunity is not restricted to the drug itself, but also involves a response to selfantigens. 

Although polyclonal antibodies have been used for passive immunization and therapeutic treatments, there are cases when hypersensitivities are induced. The reason is that polyclonal antibodies contain not only the specific antibody that binds to the desired antigen but other antibodies, which our immune system will treat as foreign substances and act against. 

The above forms of hypersensitivity must be distinguished from allergies involving the immune system (p. 72). 

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