Antigens


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Antigens

 

colloid substances of high molecular weight which, when introduced into the bodies of animals and man, stimulate the formation of specific antibodies that react with them. An indispensable condition for antigenicity is the difference of the antigen from the substances normally present in the recipient. Antigens consist principally of foreign proteins, some polysaccharides (mostly of bacterial origin), and complexes of proteins and various chemical compounds. There are corpuscular antigens—for example, suspensions of bacteria—which produce agglutination (clumping) reactions with antibodies and soluble antigens—for instance, toxins—which produce precipitation (sedimentation) reactions. Simple proteins of low molecular weight, such as gelatin proteins, are not antigenic. Egg and blood serum albumens (molecular mass 40,000–70,000) have less antigenicity than gamma globulins and other proteins with higher molecular mass (> 160,000). Lipides and carbohydrates that have no antigenic properties and that acquire them in combination with proteins are called haptens. Antigens may be synthesized artificially by combining any of a number of chemical substances with protein. Antigens contain two components, a substance of high molecular weight which is the vehicle for antigenic stimulation (usually a protein) and a nonprotein group whose structure determines the specificity of the given antigen. These groups are called determinants (or specificity factors); they are located on the surface of the antigen and may be separated from the colloid carrier. In certain pathological states—for instance, hemolytic anemia—the body’s own proteins acquire antigenic properties, that is, they become autoantigens. Since proteins have individual specificity, proteins of an animal are antigens for other animals of the same species (isoantigens). It is precisely for this reason that reactions resulting from tissue incompatibility occur in transplants (except in cases of transplant from one monovular twin to another).

References in periodicals archive ?
The endpoint concentration identifies not only the antigens to which the patient is allergic, but also the patient's level of sensitivity to them, providing a safe point for the initiation of immunotherapy.
Gilbert's group concluded that pp65, a small protein that CMV releases as soon as it infects a cell, interferes with a cell's ability either to chop up IE into antigens or to display the fragments on its surface.
Cytogen's PROSTASCINT molecular imaging agent is the first and only commercial product targeting prostate-specific membrane antigen or PSMA.
As shown in panels D, E, and F, all donors were strongly reactive to the CMV antigens (0.
After 3 weeks of acclimation to their feed regimens, rats were sensitized and 2 weeks later challenged with house dust mite (HDM) antigen via intratracheal instillation.
flexneri to synthesize the immune-stimulating antigens of another organism.
SurModics' distribution of DIARECT's recombinant autoimmune antigens in North America and Japan demonstrates our commitment to providing compelling technologies and products for the IVD market," said Bruce Barclay, President and CEO of SurModics.
This, they believed, would guarantee that the dendritic cells present the antigen properly.
Because Caspi's results might benefit uveitis patients, who must take immunosuppressants in order to retain their vision, NEI's Scott Whitcup and Robert Nussenblatt tested retinal S antigen in two patients.
helvetica were still present, but antibodies to the other three antigens were not observed, indicating that R.
Most recently, the researchers gave B-chain-linked antigens from heart grafts to mice following tissue transplants.
B-cell activation by cross-linking the B-cell antigen receptor, CD40-CD40L interactions to promote switching, TGF-bd1 by directing the switch to IgA, and Th2-type cytokines by increasing the number of post-switch Ig[A.