|
Snippets:
3.6 Immunotoxicity
The immune system is a highly evolved defence system that protects our bodies from invading organisms, tumour cells and environmental agents. Our bodies are exposed to many bacteria, viruses, fungi and parasites, which are capable of causing serious diseases such as pneumonia, malaria and typhoid fever. Fortunately, our bodies have various systems, including the immune system, that combat these invaders. Environmental chemicals or drugs that can affect the immune system are called immunotoxicants. Immunotoxicants can have three different effects on the immune system: they can suppress the immune system; they can make it hypersensitive, which causes allergies; or they can cause the immune system to attack its own body (autoimmunity).
'''''''''
Chemicals can have three different effects on the immune system:
immunosuppression
hypersensitivity/allergies
autoimmunity
'''''''''''
Table 15. Examples of immunotoxic chemicals
*snip*
Autoimmunity
dieldrin
perchloroethylene
vinyl chloride
epoxy resins
trichloroethylene
hydrazine
quartz
'''''''''''''''
As previously discussed, the immune system has ways of distinguishing host cells and substances from foreign cells and substances, which prevent the immune system from attacking its own body. When the immune system loses the ability to distinguish between the body's own cells and foreign cells, it will attack and kill host cells, resulting in serious tissue damage. This condition is called autoimmunity. Although not as common as immunosuppression or allergies, occupational exposure to certain chemicals has been associated with autoimmune responses. These include the pesticides aldrin and dieldrin, vinyl chloride, and metals such as gold and mercury. In most cases, if the exposure stops, so will the autoimmunity. This is also the case with allergies.
The immune system reacts differently to toxic substances when compared with the responses of other organ systems. The toxic response to a substance is usually dose-related, such that a high enough dose of a chemical will cause an adverse effect in most of the general population. Allergic reactions and autoimmunity, on the other hand, are usually not dose-related. Frequently only a small fraction of the population will be affected regardless of the amount of dose received. Additionally, the effects of chemicals on the immune system are related to the consequences of activating or inactivating of the immune system, rather than a direct toxic effect.
---------------------------------------------------------
http://icmr.nic.in/bujujul01.pdf
ISSN 0377-4910
Vol.31, No.6&7 June-July, 2001
IMMUNE RESPONSE TO EXPOSURE TO OCCUPATIONAL AND ENVIRONMENTAL AGENTS
****
CONCLUSIONS
Immunotoxicology is a study of interactions of chemicals, metals, drugs, etc. with the immune system.
The prime concern is to assess the importance of these interactions with regard to human health. The toxic
response may occur when the immune system is the target of chemicals resulting in altered immune function; this
in turn can result in decreased resistance to infection, certain forms of neoplasia, or immune dysregulation or
stimulation which exacerbates allergy or autoimmunity.
Alternately, toxicity may arise when the immune system responds to the antigenic specificity of the chemical as
part of a specific immune response (allergy or autoimmunity). Certain drugs induce autoimmunity.
A number of substances affect immunological parameters; these include halogenated hydrocarbons,
polychlorinated dibenzoparadioxins and polychlorinated dibenzofurans; pesticides (DDT, HCH, cyfluthrin,
malathion, etc.); organic solvents; asbestos; silica and metals like lead, cadmium, mercury. Oxidant air pollutants
like sulphur dioxide, nitrogen dioxide, ozone and air-borne dust particles may affect immune function.
The detection of immune changes on exposure to
immunotoxic agents is more complicated and difficult in
humans than in experimental animals
*snip*
---------------------------------------------------------
http://www3.sympatico.ca/cnin/toxdef.html
Toxicity Definitions
Neurotoxicity: Adverse effects on the structure or function of the central and/or peripheral nervous system caused by exposure to a toxic chemical. Symptoms of neurotoxicity include muscle weakness, loss of sensation and motor control, tremors, cognitive alterations and autonomic nervous system dysfunction. Other symptoms include memory loss, extreme fatigue, hearing impairments and/or tinnitus, dizziness, sleep disturbances, depression, pain and/or numbness of the extremeties, lightheadedness, breathing difficulties, loss of interests in hobbies, and confusion.
*snip*
Endocrine Toxicity: Any adverse structural and/or functional changes to the endocrine system (the system that controls hormones in the body) which may result from exposure to chemicals. Endocrine toxicity can harm human and animal reproduction and development.
Immunotoxicity: Adverse effects on the normal functioning of the immune system, caused by exposure to a toxic chemical. Changes in immune function could produce higher rates of infectious diseases or cancer, or more severe cases of those diseases. Immunotoxic chemicals can also cause auto-immune disease or allergic reactions.
*snip*
-------------------------------------------------------
http://wwwoud.niwi.knaw.nl/elecpubl/imwo/tnov/tnov838.htm
Discipline Report on (Bio)Medical and
Health Sciences Research in the Netherlands 1998
TNO-V | TNO-Nutrition and Food Institute
TNOV/838 Target Organ Toxicology
--------------------------------------------------------
More from the WHO's page:
http://www.who.int/pcs/training_material/hazardous_chemicals/section_2.html
Table 11. Recognized skin effects of pesticides
Pesticide
Effect
paraquat, captafol, 2,4-D, mancozeb
contact dermatitis
benomyl, DDT, lindane, zineb, malathion
skin sensitization, allergic reaction, rash
hexachlorobenzene, benomyl, zineb
photoallergic reactions
organochlorine pesticides
chloracne
hexachlorobenzene
deep scarring, loss of hair, skin atrophy
*****************************************
***
Although skin irritation commonly occurs after dermal exposure to certain chemicals, the effects of most concern are the systemic effects. After a chemical has been absorbed through the skin and has entered the systemic circulation, it can travel throughout the body and damage organs and body systems (see chapter 3).
***
2.3 Inhalation route of exposure
The lung is another common route of exposure but, unlike the skin, lung tissue is not a very protective barrier against chemical exposure.
**
Consequently, the lung tissue is very thin and allows the passage not only of oxygen, but also of many other chemicals directly into the blood. In addition to systemic damage, chemicals that pass through the lung surface may also injure the lung tissue and interfere with its vital role of oxygen supply.
If a chemical cannot become airborne, it cannot enter the lungs and, thus, cannot be toxic by the inhalation route.
|
Имунната система