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Summary of  "Classic Toxicology:
                   Chemically-Induced Immune Response Explained

From Our Toxic Times,
(April 1999, Vol 10, No 4).

 by Dr. Patrick Williams
 of  Benchmark Genetics
 Phone: 507- 645-2378

In "Classic Toxicology: Chemically-Induced Immune Response Explained,"
Dr. Patrick Williams provides an explanation, following the traditional
toxicological model, of  how the immune system reacts with toxic  chemicals.

Dr. Patrick Williams describes:

        Innate Immunity - the body’s physical and chemical barriers; blood proteins;
                                       phagocytic macrophages, neutrophils, and natural killer cells.

and Acquired Immunity - a specific immune response to each foreign agent.

Also, Dr. Patrick Williams discusses Chemical Irritants, Toxicants,
Allergens and Hypersensitivity

Chemical Irritants and Toxicants

               "Toxic effects are not produced by a chemical agent unless that 
               agent or its metabolites reach susceptible cells tissues, or organs
               within the body.  In addition, the concentration and longevity of
               the chemical in the body are critically important to the production 
               of a toxic effect ... and the susceptibility of the body.

               As in the case of chemical irritants, cellular and tissue toxicity
               results in an inflammatory response. If this occurs on the external
               surface, redness, swelling, heat, and pain will be observed.
               These same indications of inflammation occur inside the body
               as well."

Chemical Allergy

                "Chemical allergy is an immunologically mediated adverse reaction
               resulting from previous exposure (sensitisation) to a specific chemical
               or structurally similar one (hypersensitivity). Most chemicals and their
               metabolic products are not large enough to be recognized by the immune
               system as a foreign substance."

               "However, when a chemical binds with a "self" protein (called a hapten)
               it forms an antigen and can now be recognized by the immune system ...

               "This hapten-protein complex (antigen) is then capable of stimulating
               the formation of antibodies, which occurs over a 7-14 day period.
               This process is called sensitization."

Hypersensitivity can be classified into four types on the basis of immune
mechanisms and mediator molecules (this is a simplification):

     TYPE 1 - Immediate Hypersensitivity - typically mediated by IgE
                     (eg isocyanates).

     TYPE 2 - Antibody-Mediated Cytotoxic Hypersensitivity - antibodies
                     against haptens bound to cell surfaces (eg heavy metals).

     TYPE 3 - Immune Complex Mediated Hypersensitivity - deposition of antigen-
                     antibody complexes in various tissues (blood vessels and joints).

     TYPE 4 - Cell Mediated Hypersensitivity - sensitized T cells (typically in skin)
                     release cytokines in response to a secondary exposure (eg allergic
                     contact dermatitis which represents a true allergy with minute amounts
                     of chemical causing reactions -- distinct from irritant contact dermatitis
                     where the severity of the reaction is related to the dose applied.

                     Fifty (50%) of chemically sensitive patients display Type 4
                     Hypersensitivity Reactions
(Rea, 1992.)

The full article, "Classic Toxicology: Chemically Induced Immune Response Explained," (and many others on related topics) is available from:

The Chemical Injury Information Network  (CIIN) and its monthly magazine,
Our Toxic Times

To view the extensive index of past issues, please click here.

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