The origin of IgA in chicken bile: its rapid active transport from blood

In the chicken, there are two bile ducts, one draining the left lobe of the liver directly into the duodenum and the other draining the right lobe via the gall bladder. Cannulation of these ducts enabled us to collect bile in unanesthetized birds and to compare the IgA concentrations of the hepatic bile, gall bladder bile and blood serum. Bile from the cystic and hepatic ducts of the same bird contained similar amounts of IgA (1.7 mg/ml), roughly 10 times as much as in serum, but considerably less than that found in the concentrated bile collected by aspiration from the gall bladder (8 mg/ml). Ligation of the two bile ducts resulted in a three to fourfold increase in the concentration of IgA in serum suggesting that IgA is normally removed from serum by the biliary route. This was confirmed by a substantial recovery of i.v. injected, radiolabeled monoclonal dimeric human IgA in the bile corresponding to a rapid active clearance from the blood circulation; negligible amounts of monomeric human IgA, similarly injected, were recovered from the bile.

Coccidiosis: localization of lymphoblasts in the infected small intestine

Peripheral blood lymphocytes of chickens and thoracic duct lymphocytes and mesenteric lymph node cells of rats, were labelled with 125I-deoxyuridine and injected intravenously into chickens or rats respectively. Sixteen to 18 h later the intestines of coccidia infected animals contained more radioactivity than those of uninfected controls. This result was obtained with cell suspensions from both infected and normal donors indicating that, as with nematode infected rodents, the increased homing of the cells to parasitised gut was not antigen specific. In chickens the stimulus which causes the increased homing of cells to the intestine was induced within hours of parasite inoculation. This reflects the rapid response of this host, previously described with other parameters, and which may be characteristic of birds.

Immunity to coccidiosis: T-lymphocyte- or B-lymphocyte-deficient animals

Comparisons were made between infections with Eimeria spp. in normal animals and in animals with functional deficiencies in either T-lymphocytes (athymic nude rats) or B-lymphocytes (bursectomized chickens). Approximately three times more oocysts of E. nieschulzi were passed during a primary infection in the nu/nu rats, and in contrast to the nu/+ rats, they were completely susceptible to reinfection. Nu/nu rats did not produce agglutinating antibodies to sporozoites, and injections of serum from immunized nu/+ rats caused a reduction of oocyst production during a primary infection in both nu/nu and nu/+ rats. In chickens, oocyst production in primary infections with E. maxima or with E. acervulina was increased 1.5 to 2-fold in the bursectomised (BX) groups, and the clinical effects of infection with E. maxima were greater than in controls. The BX birds were slightly more susceptible than the controls to challenge inoculations of oocysts, but nevertheless, they were very substantially immune. Tests for the functioning of B- and T-lymphocytes indicated that in the BX birds there was a severe deficiency of B-cell function, but near-normal T-cell function. The results show that T-lymphocytes are essential for immunity and that, although they may function partly as helper cells for immunoglobulin production, their major effect is exerted via some other mechanism.

Peripheral blood leucocyte response to coccidial infection: a comparison of the response in rats and chickens and its correlation with resistance to reinfection

The peripheral blood leucocyte (PBL) response to infection with two species of the intestinal protozoan Eimeria shows a remarkably similar pattern in both rats and chickens. Like resistance to these parasites, the PBL response to reinfection is species-specific and it coincides with the inhibition of development of the parasite and with cellular infiltration of the lamina propria. In primary infections, the numbers of PBL increased biphasically and significant changes were found in the count of polymorphonuclear cells (PMN), lymphocytes, and large mononuclear cells (LMN). A consistent pattern of two increases in PMN, some lymphopenia, and two increases in LMN was found in rats and chickens. The response to secondary infections was more rapid and much briefer, particularly in chickens in which significant changes were detected within hours of infection and consisted of an almost equal increase in PMN and in lymphocytes. This secondary response occurred only in animals challenged with the homologous species. It was not evoked by challenge with a related species which develops in approximately the same area of the intestine.

Immunity to coccidiosis: stages of the life-cycle of Eimeria maxima which induce, and are affected by, the response of the host

An attempt was made to determine the relative importance of the different life-cycle stages of Eimeria maxima in the induction of immunity and also those stages most affected by the immune response of the host. In one experiment the life-cycle was controlled by chemotherapy but in all other experiments partial life-cycles were induced by transfers of infected mucosa between hosts. The results indicated that the second generation schizont stage is probably that most concerned in the induction of protective immunity and that sexual stages are most susceptible to immune inhibition. After initial inhibition in the immune host the earlier asexual stages were able to resume development when transferred to a susceptible host. The longer the period of exposure to the immune environment, the less able was the parasite to recover.