الفهرس 
I- IntroductionOnly 14 pages are availabe for public view
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Abstract
Animals are exposed to millions of potential pathogens daily, through contact, ingestion and inhalation. Their ability to avoid infection depends on their mechanism of innate immunity. There has been a tendency to emphasize the role of the humoral and/or cellular immunological system in defense against infection; however, it is equally clear that this system is not triggered rapidly enough to protect against exposure to pathogens.
Classic examples of host response-mediated pathogenesis that seen in diseases such as aflatoxicosis (aflatoxin Bl), the secondary toxic metabolite that produced by fungus {Aspergillus flavus) and Gram-negative bacteria (Fish pathogen; Aeromonas hydrophila) sepsis were chosen in the present study.
Animals were grouped into three groups; the first was injected i.p. once every 3 days for 21 days with 300 ug /kg b.wt. of prepared pure aflatoxinBl (AFB1), the second group was injected i.p. also, once every 3 days for 21 days with crude endotoxin of Aeromonas hydrophila (AhE) with a dose of 8 mg protein/ 0.5 ml PBSS / rat, while the third group remained as control group and injected at the same intervals by an equivalent volume (0.5 ml) of PBSS.
The data showed that the injection with AFB1 caused an increase of the total leucocytic count all over the experimental time intervals while, the injection of the crude bacterial endotoxin caused a decrease at all periods of the experiment. Regarding the differential leucocytic count AFB1 and AhE toxins decreased the lymphocytic differential count. Moreover, aflatoxin Bl decreased the monocytic differential count then it increased at the end of the experiment. Both AFB1 and AhE toxins replace the chair upon the differential count of monocytes whereas, the
former temporarily decrease the count then increase it and vice versa with the effect of AhE toxin. While the AFB1 decrease the differential count of neutrophiles, the AhE toxin appears to increase its ratio except at the
first six days post-injection. Both toxins were slightly affected the eosinophilic count. On the other hand, basophils were not detected during the injection of both toxins all over the experiment.
Regarding the total protein level, it is obvious that both toxins decrease its level in serum, conditioned medium splenocytic cell culture and cell lysate cell culture of both splenocytes and lymphocytes.
While, the both toxins decreased the albumin, (3-globulin fraction levels and A/G ratio, they increased the al, a2 and g-globulin fractions
Whereas, AFB1 decreased the phagocytic activity over all the experimental periods, crude AhE toxin caused an increased behaviour. Also, both biological toxic antigens produced more or less the same increased effect on the level of complement 3 (C3) in tested sera.
Both biological toxic antigens produced more or less the same increased effect on the total level of immunoglobulins in the serum, conditioned medium and cell lysate cell culture of both splenocytes and lymphocytes
The estimated value of the agglutination titre was increased AFB1 or AhE injection. While the agar double diffusion precipitation technique showed that injection with AFB1 was more potent than AhE toxin.
The results of cell mediated response showed that enumeration of the rosette forming cells was greatly affected as a result of intraperitoneal injection of AFB1 or AhE toxins. Also, the data of migration inhibition factor (MIF) showed that both tested toxins produced a potent effect.
Regarding the data obtained as the result of i.p. injection of AFB1, the sections of liver showed proliferation of kupffer cells associating with necrobiotic changes at the 3rd day post-injection followed by sever hyperplastic activation of the epithelial cells of bile ducts associated with disfiguration of hepatocytes. Also, the nuclear components were fragmented (Kayrolysis) and the nuclear membrane was disappeared. At the 18th day post-injection double nuclei, karyomegaly and hyperchromcia were observed in the hepatocytes in association with sever infiltration of the hyperplastic cells of bile duct. On the other hand, the liver section of the Aeromonas hydrophila endotoxin group showed proliferation of kupffer cells, enlargement of the hepatocyte size, and granular eosinophilic cytoplasm. The portal vein and sinusoids showed severe dilatation, oedema and many inflammatory cells.
Histopathological findings of the renal tissues of both tested groups revealed that the kidney sections in aflatoxin group showed the appearance of karyomegalic nuclei of epithelial cells lining renal tubules These features associated with basophilic cytoplasm, fibroblastic proliferation and dilatation of blood vessels. On the other hand, renal sections of Aeromonas hydrophila endotoxin group showed enlarged size of the endothelial cells lining the glomerular tuft associated with intracytoplasmic vacuolation.
The histopathological findings of the splenic tissue of both tested groups revealed that the spleen sections of AFB1 group showed mild hyperplasia in the lymphocytes of the white pulps, hemosiderosis in the red pulps and hyalinization in the wall of the dilated blood vessels. On the other hand, spleen sections of Aeromonas hydrophila endotoxin group showed lymphoid hyperplasia and dilatation of the blood vessels of splenic hilus associated with perivascular oedema and inflammatory cell infiltration.
The thymus sections of AFB1 group showed necrobiotic changes in the medullary cellular component associated with hyalinization in the reticular fibres, while the cortical portion showed lymphoid hypoplasia.
On the other hand, the thymus sections of the Aeromonas hydrophila endotoxin group showed depletion in thymocytes in both cortical and
medullary.
Concerning the methyl-green pyronine stain for nucleoproteins within the frozen sections of spleen and thymus for both treated and control groups, the obtained data showed that aflatoxinBl injection resulted in mild activation of the lymphoblasts in spleen sections. While, spleen sections of the Aeromonas hydrophila endotoxin (AhE) groups showed wide hyperactivation and hyperplasia of the germinal center that associated with more pyroniphilic cells.
Regarding the thymus sections, methyl-green pyronine stain showed that the aflatoxinBl has no remarkable effect upon the nucleoproteins within the studied frozen sections all over the experimental period. On the other hand, the injection with Aeromonas hydrophila endotoxin (AhE) showed a wide active germinal center associated by the presence of many of pyroniphilic lymphoblasts.
The present work illustrates the negative following effects of the mycotoxin; aflatoxinBl on:
Immune system, whereas the aflatoxinBl weak the different Cells like neutrophils, lymphocytes and monocytes, and causes different histological disorders on the immune tissues (spleen and thymus) associated with other pathological disorders of the liver.
Immune response, whereas the aflatoxinBl attenuates both the innate response (e.g. phagocytic activity) and the cellular one (T-cell response) more than the’u\humoral response (antibody production), thus increasing the susceptibility of the animal to infection by many diseases hich may lead to its death or cause severe loss in the animal mass poduction.
Protein synthesis, whereas it is found that the aflatoxinB 1 causes damage in the hepatocytes which are responsible for the synthesis of protein in the body. This damage effect was arising by the direct intact conjugation between the toxin and the hepatocytic nucleo-acids (DNA and RNA) which lead to the diminution of the protein production ability of the animal.
In addition, the present work proved the negative effects of the bacterial toxins (endotoxins of Aeromonas hydrophila) as follows:
1- Enhancing both the humoral and the cellular immune responses to secrete some ions and chemical mediators that finally cause necrotic and inflammation effects on the different body cells.
2- Causing a temporal increase in the efficacy of the reaction between the splenocytes and the thymocytes with antibodies by secreting the nucleic acids that are responsible for the production of different constituents of the immunological responses (antibody production, agglutinin proteins and precipitated proteins).
Final conclusion
In conclusion, the present study dedicated that both fungal (AflatoxinB 1) and bacterial toxins (endotoxin of Aeromonas hydrophila) were from the most factors that attenuate the immune response of the body, thus leading to increase the susceptibility of the animal mass production and fish production to the infection with different diseases. Recommendation and future work: The present study recommended the followings:
1-The study of the different effects of the fungal and the bacterial toxins should be directed to the molecular level rather than to the cell level to illustrate the mechanisms of interaction between them and other toxins
2- The activation of the immune system should be tested via different ways either by various activators or immunomedulators with different doses to show the best strategies for the treatment and protection against such toxins.
3- Different tests for detection of these toxins should be applied on both the food and water sources of fish and animals to prevent their pollution with these harmful toxins.