The influence of the bursa on Fabricius, spleen and thymus on the course of Plasmodium lophurae infections in chickens
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"Splenectomized chicks were severely deficient in their ability to combat an infection or reinfection with Plasmodium lophurae. Infection of splenectomized chicks usually caused death while sham-operated controls recovered. Birds splenectomized on the 5th day of an infection, when parasitemias had dropped to a low level, showed an immediate and usually fatal recrudescence. Chicks which were hormonally or surgically bursectomized on the 1st day after hatching demonstrated higher parasitemias then their sham-operated controls. However, parasitemias of birds bursectomized at 18 days of age did not differ from their control group. Thymectomy had no significant effect on the resultant parasitemias. It is thus concluded that the spleen is of primary importance in the development of immunity to this strain of Plasmodium lophurae. The bursa is of secondary importance and contributes something to the development of the immune mechanism before 18 days of age. Bursaless birds demonstrated higher initial gamma-1, beta-1, beta-2, alpha-1 and alpha-2 values than sham operated control groups. These high mean values in the bursaless birds decreased during the malarial infection to a low level on about day four of the infection. The infected control group showed no decrease; in fact, an increase was often observed in this group. On the other hand, low albumin and gamma-2 titers were obtained in the bursaless groups. These altered protein changes were most apparent in the hormonally bursectomized groups, and especially in the thymectomized-hormonally bursectomized group. The plasma protein values of the thymectomized group were similiar to those of the sham operated infected birds. The major plasma protein response to the injected malarial parasites in the sham operated infected group was an increase in gamma-1 globulin. An early peak was noted on day two of the infection as well as an increase from day ten to fifteen. This response did not appear in any of the bursaless groups or in the non-infected group. The possible significance of a relationship between the high alpha and low gamma-2 globulin levels of bursaless birds is discussed. Antimalarial antibodies were detected in the plasma of normal birds which recovered from infection with P. lophurae. These antibodies were detected as specific antiparasitic agglutinins in normal birds. These agglutinins were not detected in the plasma of bursaless birds which had been infected and reinfected. The administration of hyperimmune plasma to bursaless and normal birds resulted in highly depressed parasitemias. Interestingly, infected bursaless birds which were given normal plasma from mature cockerels demonstrated parasitemias which were depressed to the level of parasitemias of intact infected birds. This indicated that bursaless birds lack a natural antibody which birds normally develop. Splenectomized-infected birds which received hyperimmune plasma eventually recovered from an infection. Splenectomized—controls, however, succumbed to the infection. The surviving splenectomized birds subsequently demonstrated an ability to control the parasites, as attempts to reinfect these birds failed. It was postulated that in the absence of the spleen and during intense antigenic stimulation, other lymphoid centers develop which are able to participate in normal anamnestic reactions."--Summary.
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