Antigen

“ Immune body or amboceptor is the name given to a substance present in the serum of an infected animal that has successfully resisted inoculation with some particular micro-organism, and which possesses the power of linking the complement normally present in the serum to bacteria of the species used as antigen in such a manner that the micro-organisms are rendered innocuous, and ultimately destroyed. ”

“ Alcoholic extracts of beef heart are most commonly used. Details of this test may be learned in the advanced course in Immunity and Serum Therapy.
The complement-fixation test might be applied to the determination of unknown bacteria, using the unknown culture as antigen and trying it with the sera of different animals immunized against a variety of organisms, some one of which might prove to furnish specific amboceptor for the unknown organism and hence indicate what it is. ”

“ The process by which passive immunity is acquired depends upon the fact that as a result of the reaction between the specific virus of a particular disease (the antigen) and the tissues of the animal attacked, certain substances—antibodies—are produced, which when transferred to the body of a susceptible animal protect it against that disease. The most important of these antibodies are the antitoxins. From the study of the processes by which immunity is secured against the effects of bacterial action the serum and vaccine methods of treating certain infective diseases have been evolved. ”

“ Examples might include the findings of the presumptive biomarker identification with the addition of a positive PCR, ELISA, or electrochemiluminescence (ECL) results, using specific target nucleic acid sequences for the organism and antibody recognition of agent-specific antigen sites, respectively. ”

“ The substance within the introduced cell which acts as a stimulus (antigen) to the body cells is called an “agglutinogen.” That “agglutinogen” is present in the cell has been shown by injecting animals experimentally with extracts of cells (bacterial and other cells) and the blood serum of the animal injected showed the presence of agglutinin for the given cell. It will be noticed that the receptors which become the free agglutinins have at least two functions, hence at least two chemical groups. ”

“ Complement Fixation.—Complement fixation tests have been employed in the diagnosis of several tropical diseases but do not seem to be at present sufficiently reliable or practical with the exception of that for yaws and tularaemia. The chief difficulty with complement fixation tests for suspected sera is to obtain a reliable antigen. Should we later on be able to prepare bacterial antigens as satisfactory as Noguchi’s acetone-insoluble antigen is for the Wassermann test there may be a field for such tests in tropical pathology. ”

“ The molecules which lead to the production of anti-substances are usually known as antigens, and each antigen has a specific combining affinity for its corresponding anti-substance, fitting it as a lock does a key. The antigens, as already indicated, may occur in bacteria, cells, &c., or they may occur free in a fluid. Anti-substances may be arranged, as has been done by Ehrlich, into three main groups. ”

“ Infected cells commonly seen in the lung of fetuses that develop a high titer of antibody for PPV probably represent this stage of replication (see Fig. 17.8C) . Affected cells subsequently round up, become pyknotic, and disintegrate with release of virus and viral antigen (Fig. 17.2B) . Other cells in the culture that are not at the appropriate stage to support viral replication continue to phagocytize and accumulate viral antigen in their cytoplasm (Fig. 17.2C) . ”

“ The protein used as antigen to stimulate its formation, or some part of the protein molecule (haptophore group) , which acts as stimulus to the cell is spoken of as a “precipitinogen,” both terms after the analogy of “agglutinin” and “agglutinogen.” In fact the specific precipitation and agglutination are strictly analogous phenomena. Precipitins act on proteins in (colloidal) solution and cause them to settle out, agglutinins act on substances within cells which cells are in suspension in a fluid and cause the cells to settle out. ”

“ Still, after having used vaccines on human beings and animals for twenty-one years, and observing that plant life reacts to an antigen in a similar manner, I am at least entitled to the same conclusions. This gives me an opportunity of knowing years in advance just what to expect.
While my work is still going on as an experiment I have no hesitancy in saying that I can and have put as much active immunity to the blight into the chestnut in five years as nature has been able to place in perhaps four or five thousand years by her usual method. ”

“ T lymphocytes: also called T cell. They are an important type of lymphocytes that maintain the immune system and are essential to fight against pathogenic microorganisms. There are two main types of T lymphocytes, Cytotoxic T cell (Tc) and the T helper cells (Th) . The Tc look for antigen infected cells in the body. When a Tc recognizes an antigen bound to a cell, it adheres to the surface of the infected cell and produces toxic molecules, killing the cell. ”

“ Individuals vary just as much in susceptibility and hence in reactive power, and generally speaking, an individual will react better in the production of antibodies to a stimulus to which he has been more or less subjected, i.e., to organisms derived from his own body.
In the preparation of a vaccine great care must be used in heating so that the organisms are killed, but the antigens are not destroyed. Many of the enzymes present in bacteria, especially the proteolytic ones, are not any more sensitive to heat than are the antigens, hence are not destroyed entirely. ”

“ An agglutination test involving the use of growing culture as antigen was developed by Wellmann (1955) . In this test, called the Wachstumsprobe or growthagglutination test, a culture of E. rhusiopathiae growing in liquid medium in the presence of sterile test serum agglutinates if sufficient specific antibody is present.
No serologic test has proved useful for routine diagnosis of acute infection or for differentiation between immune and susceptible pigs. Serologic diagnosis may have some value in detection of chronic infection, primarily on a herd basis. ”

“ Hemadsorption, secondary adult porcine thyroid cells, guinea pig erythrocytes, 22 hours after thyroid cells were infected and then subcultured (May-Grünwald-Giemsa; ×100) . Several investigators have used IF microscopy to follow the development of PPV in cell culture (Cartwright et al. 1969; Lucas and Napthine 1971; Mengeling 1972; Siegl et al. 1972; Bachmann and Danner 1976) . In general, the sequence of events is as follows. Viral antigen is detected in the cytoplasm of cells soon after infection if the inoculum contains a high titer of virus and viral antigen. ”

“ Human immune serum shows no reaction with the blood of any animals except to a slight extent with that of various monkeys, most with the higher, very slight with the lower Old World and scarcely any with New World monkeys.
It is a fact of theoretical interest mainly that if agglutinins and precipitins themselves be injected into an animal they will act as antigens and cause the formation of antiagglutinins or antiprecipitins, which are therefore receptors of the first order since they simply combine with these immune bodies to neutralize their action, have only a combining or haptophore group. ”

“ In addition to the clinical applications of therapy and diagnosis, monoclonal antibodies have also proven to be superior tools for studying viral antigenicity, evolution, and for the treatment of acute viral disease in humans [8] , [24] , [47] , [48] . ”

“ Again, antibodies may be formed in response to antigens other than infective particles—thus the injection into suitable animals of foreign proteins such as egg albumin, heterologous blood sera or red blood discs from a different species of animal, will result in the formation of specific antibodies possessing definite affinities for their respective antigens. ”

“ One is difficulty in expressing conformationally correct large antigens and scaling up the methods needed to do this to the extent that would allow large-scale manufacture. A second challenge has been the only modest antibody responses achieved even with a range of new adjuvants. ”

“ We also identified the location of several defined epitopes which evolve over time and drive antigenic change. Our data indicate that antibodies targeting these sites block carbohydrate binding and likely select for the emergence of new strains that escape herd immunity and recognize unique carbohydrates for entry, resulting in new outbreaks of disease in vulnerable human populations. Importantly, these studies critically inform the rational design of broadly active vaccines and immunotherapeutics for the treatment of norovirus disease. ”

“ Gaz., Nov., 1896. ↑ * The Bordet-Gengou reaction is based on the fixation of the complement, using a culture of the vibrio as an antigen. The following mixtures are prepared in three test tubes: Nos. 1 and 2 contain 0.2 c.c. suspension of cholera vibrio, and 0.6 c.c. suspected person's serum (heated to 56° F. for half an hour) , and 0.1 c.c. complement (guineapig's serum) ; tube 3, a similar mixture with the substitution of normal person's serum. These tubes are shaken and incubated for half an hour. ”

“ Neutralizing antibodies derived from the B cells of 1918 influenza pandemic survivors. Nature. 2008;455:532–536.187166251 2 Tan M, Hegde RS, Jiang X. The P domain of norovirus capsid protein forms dimer and binds to histo-blood group antigen receptors. J Virol. 2004;78:6233–6242.15163716↑ Choi JM, Hutson AM, Estes MK, Prasad BV. Atomic resolution structural characterization of recognition of histo-blood group antigens by Norwalk virus. ”

“ These data absolutely underscore the critical importance of determining the structures of several of these human mAbs with their appropriate GII.4 VLP epitopes by either cryoEM or crystallography, for informing targeted mutagenesis to identify the role of key residues in regulating antigenicity and antibody escape. ”

“ Differences in bovine lymphocyte antigen associations between immune responsiveness and risk of disease following intramammary infection with Staphylococcus aureus. J Dairy Sci 78:1937-1944.
Meeker, D. L.; Rothschild, M. F.; Christian, L. L.; Warner, C. M.; and Hill, H. T. 1987a. Genetic control of immune response to pseudorabies and atrophic rhinitis vaccines. I. Heterosis, general combining ability and relationship to growth and backfat. J Anim Sci 64:407-413.
___. 1987b. Genetic control of immune response to pseudorabies and atrophic rhinitis vaccines. ”

“ Their data indicate, however, that even though changes in the immunological characteristics of proteins are brought about by formolization, the proteins retain enough of their specific chemical characteristics to allow consistent differentiation of species by immunological methods. In the tests which I performed, the relative positions of the precipitin curves, whether native or formolized extracts were involved, remained unchanged (Figs. 10, 11) . All data used in interpretation of the serological relationships were obtained from tests in which formolized antigens of equivalent age were used. ”

“ But in certain directions, notably in regard to the relations with micro-organisms, changes in the blood-plasma can be made out, though they are not associated in all cases with changes in the formed elements which float in it, nor with any obvious microscopical or chemical alterations.
The phenomena of immunity to the attacks of bacteria or their toxins, of agglutinative action, of opsonic action, of the precipitin tests, and of haemolysis, are all largely dependent on the inherent or acquired characters of the blood serum. It is a commonplace thatImmunity. ”

“ Ways of detecting adulteration in foods, particularly foods from animal sources, and of differentiating proteins of varied origin, as well as means of establishing biological relationships and differences among groups of animals through “immunity reactions” of blood serums have followed from knowledge gained by application of the facts or the methods of immunity research. Hence the study of “immunity problems” has come to include much more than merely the study of those factors which prevent the development of disease in an animal or result in its spontaneous recovery. ”

“ The question of the value of preventive inoculation is, however, still an open one. So also are other applications of the principles of immunity, as the production of anti-sera for snake-venom, and for the irritant (and perhaps intoxicating) vegetable agent causing hay fever.
I have earlier in this lecture referred to methods of serum diagnosis depending on agglutination or solution of bacteria or on the precipitation of protein. Immunology has recently contributed to medicine another diagnostic method of great value. ”

“ The increased ingestion of bacteria in active immunity would seem to depend upon the presence of immune opsonins in the serum. These, as already explained, are true anti-substances. Thus the apparent increased activity of the leucocytes is due to a preliminary effect of the opsonins on the bacteria. We have no distinct proof that there occurs in active immunity any education of the phagocytes, in Metchnikoff’s sense, that is, any increase of the inherent ingestive or digestive activity of these cells. ”

“ Of the chief methods used in producing active immunity the first is by inoculation with bacteria whose virulence has been diminished, i.e. with an “attenuated virus.” Many of the earlier methods of attenuation were devised in the case of the anthrax bacillus, an organism which is, however, somewhat exceptional as regards the relative stability of its virulence. Many such methods consist, to speak generally, in growing the organism outside the body under somewhat unsuitable conditions, e.g. at higher temperatures than the optimum, in the presence of weak antiseptics, &c. ”