الفهرس 
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Abstract
Fasciolias is is a world wide problem caused by the parasitic trematode r: gigantica and F. hepatica. It is a destructive disease of liver causing economic losses in the animal husbandry industry . Although disease sequelae due to Fasciola infection in man are not as severe as in sheep and cattle, it may cause considerable morbidity and infrequently death, representing a major health problem particularly in developing countries. The aim of this study was to isolate the antigenic fraction of Fasciola gigantica worms obtained from condemned livers. It also aimed at studying the possibility of induction of some sort of homologous immunity by both crude and purified antigens against challenge infection with r: gigantica. This study was carried out on 150 mice of Swiss albino strain, and 70 rabbits of New Zealand strain. Collection of worms from condemned livers was through local abattoir in Alexandria. The metacercariae were purchased from Raymond Cropper, Gayton house, England, and kept at + 4°C. The purified antigens were isolated from crude extract utilizing two chromatographic fractionations including: column chromatography (molecular sieving) and ion-exchange chromatography. Using sephadex G 50 and sephadex A-I 20 respectively. The purified antigen was isolated in the form of three peaks categorized I, 11 and Ill. The molecular weight was determined by SDS-PAGE, finding that the major component of the 3rd peak was 12 KD protein. Antigens were injected subcutaneously with Freund’s adjuvant, weeks apart. Animals utilized in 2 doses 2 immunization experiments were grouped as follows: Group A: Animals immunized with crude extract of gigantica. Each rabbit received a total dose of 750 pg and each mouse received a total dose of 100 pg prior to challenge \\..jth fasdola gigantica metacercariae 30 for each rabbit c:md 3 for each mouse. Group B: Animals immunized with purified antigen of t: gigantka. They were subgrouped into 3 subgroups I, If, III and received the corresponding isolate. Each rabbit received a total dose of 500 pg and each mouse received a total dose of 1 0 ~g prior to challenge infection with r: giganUca similar to the previous one, Group C: Animals received Freund’s adjuvant only followed by t: gigantica infection. The results of the present study showed that rnice of Albino Swiss strain was not suitable for Fasciola gigantica infection as 60 percent of them died 7 days post infection and the rest didn’t show any worms one month later. On the other hand vaccination of rabbits with crude antigen induced 60 percent reduction in worm burden over the controls. However vaccination of rabbit5 with purified antigen induced reduction in worm burden which reached up to 80 percent (using the 3rd isolated purified antigen, 12 KD). The reduction in worm load was attributed to the possibility . of antibody interference with the ability of the migrating flukes to reach the imrnunologically safe environment of bile ducts or killing of the challenge invading flukes by the effector cells. As regards, the effect on worm length: there was reduction in worm length which was statistically significant using student’s t test. Worm length ranged from 1.4 cm (using purified antigen HI) to 1.7. cm (using crude antigen). This was attributed to interference with maturation of flukes which is one of the causes of reduction in worm fecundity. The current study showed reduction of egg excretion as evidenced by marked diminution in stool egg count. This reduction was attributed to diminished worm fecundity and secondary to reduced worm load. Also egg destruction by e