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IMMUNOLOGICAL MECHANISMS AGAINST BACTERIA AND PARASITES. |
Both the innate and adaptive immune responses have a large number of mechanisms to fight against bacterial and parasitic infections. |
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Immune response against bacteria |
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One useful
classification, which is according to the surface of the bacteria could be:
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Aspect of GRAM (-) bacteria (Salmonella) in XLD culture medium
Aspect of Staphylococcus aureus colonies (GRAM (+)) in agar-blood. |
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Tthe most effective mechanism for destroying the bacterial membrane of Gram-positive bacteria, is phagocytosis; while for Gram-negative, mycobacteria and spirochetes (due to their double lipid envelope), the most effective way is cytotoxicity, mediated by complement and cytotoxic cells. The effectiveness of the immune mechanisms will be different depending on the pathogenic mechanism of the infectious agent (direct effect or toxins). For example: bacteria that produce toxins are effectively attacked by antibodies, while in pathologies directly related to the bacteria, cytotoxicity mechanisms will be more effective. |
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As part of the adaptive
immune response, antibody production plays a main role based on
several mechanisms: neutralization of bacterial toxins, mucosa
protection (IgA) and activation of the complement by the classical
pathway, which produces the destruction of bacteria or activating phagocytosis
by the stimulation of the Fc receptor. Phagocytosis is one of the most
effective mechanisms against bacteria, so the release of cytokines is of
great importance in this kind of infections. |
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Parasitic diseases have an important economic relevance in the swine species
Due to the complexity of their structures however, the real immunological mechanisms acting against parasites are not well known. The main characteristics of the immune response against parasites can be summarized in the following points: |
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Main mechanisms of innate and adaptive responses against parasites Even though parasites are very antigenic, not all of the responses that they induce are effective. This is mainly due to the fact that they produce different antigens during the different stages of their cycles. The immunological fight against parasitic diseases is still very limited. |
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We can conclude that the phagocytosis mechanism
is related to the first stages of the parasitic
infection. |
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CHAPTER 7 | Previous theme | Bibliography | Course program |