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ADVERSE EFFECTS ADJUVANTS VACCINES Adjuvants are chemical substances which are added to vaccines to boost immune response, but they can also cause a wide range of adverse side effects. Part 2 of 2 [Editor's Note: This article refers to research studies involving animals. We wish to advise readers that we at NEXUS do not condone or support the validity, efficacy or morality of animal experimentation or vivisection.] IMMUNOLOGY PRINCIPLES: ANTIBODY RESPONSE o explain the action of adjuvants, we should look into immunology. The theory of vaccine efficacy is based on the ability of vaccines to evoke the formation of antibodies. This is of varying efficacy, depending on the nature of the antigen(s) and the amount of antigenic substance administered. However, the mechanisms for the diversity of immune reactions are complex, and to this day are not quite known and understood. There are numerous theories, the favoured one being antibody response as the sign of immunisation (acquiring immunity). Specific immunity to a particular disease is generally considered to be the result of two kinds of activity: the humoral antibody and the cellular sensitivity. The ability to form antibodies develops partly in utero and partly after birth in the neonatal period. In either case, immunological competence—the ability to respond immunologically to an antigenic stimulus—appears to originate with the thymic activity. The thymus initially consists largely of primitive cellular elements which become peripheralised to the lymph nodes and spleen. These cells give rise to lymphoid cells, resulting in the development of immunological competence. The thymus may also exert a second activity in producing a hormone-like substance which is essential for the matura- tion of immunological competence in lymphoid cells. Such maturation also takes place by contact with thymus cells in the thymus. Stimulation of the organism by antigen results in proliferation of cells of the lymphoid series accompanied by the formation of immunocytes, and this leads to the antibody pro- duction. Certain lymphocytes and possibly reticulum cells may be transformed into immunoblasts, which develop into immunologically active ("sensitised") lymphocytes and plasmocytes (plasma cells). Antibody formation is connected with plasma cells, while cellular immunity reactions are mainly lymphocytic. None of the theories for antibody formation comprehends all the biological and chemi- cal data now available. However, several principal theories have been considered at length. The so-called instructive theory holds that the antigen is brought to the locus of anti- body synthesis and there imposes in some way the synthesis of the specific antibody with reactive sites which are complementary to the antigen. The clonal selection theory, evolved by Burnett (1960), presupposes that the informa- tion requisite to the synthesis of the antibody is part of the genetics. While the body develops a wide range of clones of cells necessary to cover all antigenic determinants by random mutation during early embryonic life, those clones which are capable of reacting with antigens of the body ("self") are destroyed, leaving only those cells which are not ori- ented to self ("non-self"). Upon stimulation by a foreign antigen, the clones of the cells corresponding to the particular foreign antigen are stimulated to proliferate and to produce the antibody. Other researchers demonstrated that there are at least four different antigens formed by descendants of a single cloned cell. By this mechanism, the information for antibody syn- thesis is contained in the genetic material of each cell (DNA) but is normally repressed. The antigen then assumes the role of a de-repressor and initiates (provokes) the RNA syn- thesis for a particular messenger, resulting in the corresponding antibody production. The by Viera Scheibner, PhD © 2000 178 Govetts Leap Road Blackheath, NSW 2785 Australia Telephone: +61 (0)2 4787 8203 Fax: +61 (0)2 4787 8988 178 Govetts Leap Road Blackheath, NSW 2785 Australia Telephone: +61 (0)2 4787 8203 Fax: +61 (0)2 4787 8988 NEXUS 41 FEBRUARY — MARCH 2001