Histopathologic Changes in Lymphoid Organs During Plasmodium Lophurae Infections in Thymectomized and Bursectomized Chickens

Bryan M. LongeneckerDepartment of Zoology, University of Missouri, Columbia, Missouri 65201

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Robert P. BreitenbachDepartment of Zoology, University of Missouri, Columbia, Missouri 65201

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After infection with Plasmodium lophurae, the spleens and bursae of thymectomized chickens were significantly smaller than those of intact, infected birds. The mean ratio of bursa weight to body weight in female birds was significantly greater than the mean ratio of the males in both infected groups. Two basic types of follicular degeneration occurred in the bursa as a result of the infection, the first being a simple loss of cells from the medullary region, whereas the second led to the complete destruction of the follicle and its replacement by interfollicular connective tissue. During particularly severe infections, practically all bursal follicles degenerated. Lymphocytic depletion occurred in the spleen by day 2 of the infection, and lymphoid regeneration began by day 6. The reparative events in the spleen appeared to proceed as well in bursectomized as in normal birds. Although results from thymectomized birds were inconclusive, there was some indication that non-nodular lymphoid regeneration might be under thymic control. After infection, the amount of thymic medullary tissue increased at the expense of cortical tissue. In addition, cellular degenerative changes were noted in the medulla. Lymph nodules often appeared in the thymic medulla. The female thymectomized birds had earlier, depressed-peak parasitemia as compared with male thymectomized birds or sham-operated controls.

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