Leukocytic response and composition of enteral microbiota in chickens fed a sage extract supplemented diet and infected with Salmonella Enteritidis PT4

The effects of sage on the enteral microbiota and leukocytic response of chickens challenged with Salmonella Enteritidis (SE) PT4 were studied. Chickens were divided into four groups: control, sage (S), SE and sage+S. Enteritidis (SSE). Groups S and SSE were fed sage extract (8.2 g kg^?1) for 21 days. Groups SE and SSE were challenged with SE (10⁸ CFU) on day 4. The administration of the sage extract to the SSE group confirmed the selective antibacterial activity on SE, and resulted in an increased number of leukocytes, lymphocytes, heterophils and phagocytic activity index at day 3 post-infection. In the early phase of the infection, there was a tendency to increase the numbers of CD3+, CD8+ and IgM+ cells in the SSE group. The later phase led to a decrease of IgM+, CD3+ and CD4+ cells, but an increase in influx of macrophages, which suggested their movement into inflammatory regions.     

Heat stress impairs performance and induces intestinal inflammation in broiler chickens infected with Salmonella Enteritidis

Stressful situations reduce the welfare, production indices and immune status of chickens. Salmonella spp. are a major zoonotic pathogens that annually cause over 1 billion infections worldwide. We therefore designed the current experiment to analyse the effects of 31±1°C heat stress (HS) (from 35 to 41 days) on performance parameters, Salmonella invasion and small intestine integrity in broiler chickens infected with Salmonella Enteritidis. We observed that HS decreased body weight gain and feed intake. However, feed conversion was only increased when HS was combined with Salmonella Enteritidis infection. In addition, we observed an increase in serum corticosterone levels in all of the birds that were subjected to HS, showing a hypothalamus–pituitary–adrenal axis activation. Furthermore, mild acute multifocal lymphoplasmacytic enteritis, characterized by foci of heterophil infiltration in the duodenum, jejunum and ileum, was observed in the HS group. In contrast, similar but more evident enteritis was noted in the heat-stressed and Salmonella-infected group. In this group, moderate enteritis was observed in all parts of the small intestine. Lastly, we observed an increase in Salmonella counts in the spleens of the stressed and Salmonella-infected chickens. The combination of HS and Salmonella Enteritidis infection may therefore disrupt the intestinal barrier, which would allow pathogenic bacteria to migrate through the intestinal mucosa to the spleen and generate an inflammatory infiltrate in the gut, decreasing performance parameters.     

Overcrowding stress decreases macrophage activity and increases Salmonella Enteritidis invasion in broiler chickens

Overcrowding stress is a reality in the poultry industry. Chickens exposed to long-term stressful situations present a reduction of welfare and immunosuppression. We designed this experiment to analyse the effects from overcrowding stress of 16 birds/m² on performance parameters, serum corticosterone levels, the relative weight of the bursa of Fabricius, plasma IgA and IgG levels, intestinal integrity, macrophage activity and experimental Salmonella Enteritidis invasion. The results of this study indicate that overcrowding stress decreased performance parameters, induced enteritis and decreased macrophage activity and the relative bursa weight in broiler chickens. When the chickens were similarly stressed and infected with Salmonella Enteritidis, there was an increase in feed conversion and a decrease in plasma IgG levels in the stressed and Salmonella-infected birds. We observed moderate enteritis throughout the duodenum of chickens stressed and infected with Salmonella. The overcrowding stress decreased the macrophage phagocytosis intensity and increased Salmonella Enteritidis counts in the livers of birds challenged with the pathogenic bacterium. Overcrowding stress via the hypothalamic–pituitary–adrenal axis that is associated with an increase in corticosterone and enteritis might influence the quality of the intestinal immune barrier and the integrity of the small intestine. This effect allowed pathogenic bacteria to migrate through the intestinal mucosa, resulting in inflammatory infiltration and decreased nutrient absorption. The data strengthen the hypothesis that control of the welfare of chickens and avoidance of stress from overcrowding in poultry production are relevant factors for the maintenance of intestinal integrity, performance and decreased susceptibility to Salmonella infection.     

Salmonella enterica Serovar Enteritidis Ghosts Carrying the Escherichia coli Heat-Labile Enterotoxin B Subunit Are Capable of Inducing Enhanced Protective Immune Responses

The Escherichia coli heat-labile enterotoxin B subunit (LTB) is a potent vaccine adjuvant. Salmonella enterica serovar Enteritidis ghosts carrying LTB (S. Enteritidis-LTB ghosts) were genetically constructed using a novel plasmid, pJHL187-LTB, designed for the coexpression of the LTB and E lysis proteins. S. Enteritidis-LTB ghosts were characterized using scanning electron microscopy to visualize their transmembrane tunnel structures. The expression of LTB in S. Enteritidis-LTB ghost preparations was confirmed by immunoblot and enzyme-linked immunosorbent assays. The parenteral adjuvant activity of LTB was demonstrated by immunizing chickens with either S. Enteritidis-LTB ghosts or S. Enteritidis ghosts. Chickens were intramuscularly primed at 5 weeks of age and subsequently boosted at 8 weeks of age. In total, 60 chickens were equally divided into three groups (n = 20 for each): group A, nonvaccinated control; group B, immunized with S. Enteritidis-LTB ghosts; and group C, immunized with S. Enteritidis ghosts. Compared with the nonimmunized chickens (group A), the immunized chickens (groups B and C) exhibited increased titers of plasma IgG and intestinal secretory IgA antibodies. The CD3⁺ CD4⁺ subpopulation of T cells was also significantly increased in both immunized groups. Among the immunized chickens, those in group B exhibited significantly increased titers of specific plasma IgG and intestinal secretory IgA (sIgA) antibodies compared with those in group C, indicating the immunomodulatory effects of the LTB adjuvant. Furthermore, both immunized groups exhibited decreased bacterial loads in their feces and internal organs. These results indicate that parenteral immunization with S. Enteritidis-LTB ghosts can stimulate superior induction of systemic and mucosal immune responses compared to immunization with S. Enteritidis ghosts alone, thus conferring efficient protection against salmonellosis.     

Immunopathology of chickens infected in vivo and at hatching with the avian osteopetrosis virus MAV.2–0

The immunological capacity of chickens infected with MAV.2–0, an avian osteopetrosis virus, was studied both morphologically and functionally. Infection of 11 to 12-day-old embryos with a high (0.58 × 10⁶-1.2 × 10⁶ plaque-forming units; PFU) and an intermediate (5.8 × 10⁴ PFU) dose of virus resulted in severe stunting, as manifested by lower body and lymphoid organs (bursa, thymus and spleen) weights. The bursa and spleen of osteopetrotic chickens were poorly developed, the thymus partially necrotized; all lymphoid organs had fewer lymphocytes than controls, and there were far fewer germinal centers in the spleen of infected birds, as compared to controls. The humoral and cellular immunity of these osteopetrotic chickens was significantly suppressed, as assessed by (a) the plaque-forming cell response against sheep red blood cells (SRBC) in the spleen; (b) circulating antibody responses against SRBC, Brucella abortus and human γ-globulins (HGG); (c) the delayed hypersen-sitivity reaction against HGG; and (d) mitogenic responsiveness of peripheral blood and spleen lymphocytes to concanavalin A, phytohemagglutinin M and pokeweed mitogen. A few birds, infected as 11-day embryos with the lowest concentration of virus (2.9 × 10⁴ PFU) had no palpable bone lesions, the lymphoid organs had normal histology, and immune responses were quite similar to those in uninfected control birds. Osteopetrotic chickens, infected within 48 h after hatching (5.8 × 10⁵ PFU), had normal IgM-class antibody responses against all antigens studied (SRBC, Brucella, HGG), whereas IgG and/or IgA responses tended to be lower than those observed in the normal controls. These findings, together with the regularly organized small lymphoid follicles in the bursa, indicate a late affection of B cell development, whereas in the birds infected at 11–12 days of incubation, an almost total arrest of B cell development was observed. T cell functions of birds infected at hatching were suppressed to the same extent as those of in ovo infected birds indicating susceptibility of the T cell lineage to MAV.2–0 also at later stages of development.     

Effect of an Enterococcus faecium probiotic on specific IgA following live Salmonella Enteritidis vaccination of layer chickens

Probiotics and immunization are being widely adopted by the poultry industry with the goal of controlling Salmonella enterica. However, the interaction between these two management protocols has been sparsely studied. The present study aimed to understand the role of an Enterococcus faecium probiotic in the production of salmonella-specific IgA in layers immunized with a live vaccine. Four groups were used: “Control” (no vaccine or probiotic); “Probiotic” (which received an E. faecium product); “Vaccine” (immunized with two doses of a live attenuated S. Enteritidis vaccine); and “Vaccine?+?probiotic”. Faecal salmonella-specific IgA was analysed 7 and 20 days post-vaccination (dpv) boost. At 7 dpv, the “Vaccine” and “Vaccine?+?probiotic” groups had similar IgA levels. However, at 20 dpv, IgA levels were two times higher in the “Vaccine?+?probiotic” group compared to the “Vaccine” group. To understand the role of the intestinal microbiota in this finding, bacterial diversity in faeces was analysed by 16S rRNA gene sequencing. The improvement in IgA production in probiotic-treated birds was accompanied by marked changes in the faecal microbiome. Some of the main differences between the “Vaccine” and “Vaccine?+?probiotic” groups included reduction of Escherichia-Shigella and increases in Blautia, Anaerotruncus and Lactobacillus in the latter group. Although no direct causal link can be established from this study design, it is possible that the E. faecium probiotic induces improved antibody production following vaccination via modulation of the intestinal microbiota.     

Individual and combined effects of ochratoxin A and Salmonella enterica serovar Gallinarum infection on pathological changes in broiler chickens

A study was conducted to evaluate the individual and combined effects of ochratoxin A (OA) and Salmonella enterica serovar Gallinarum (S. Gallinarum) on gross and histopathological changes in broiler chickens. One hundred and seventy-six 1-day-old broiler chicks were divided into two groups of 88 chicks each; one group was fed a control mash diet, and the other group was fed a mash diet containing 2 parts/10⁶ OA. On day 14, each group was further subdivided into two groups, with one group inoculated with S. Gallinarum intraperitoneally (1.25×10¹⁰ colony-forming units/0.5ml) whereas the other group was not inoculated with S. Gallinarum. Four birds from each group were sacrificed on 1, 2, 3, 5, 7, 10, 14 and 21 days post inoculation to record pathological changes in different organs. Gross and microscopic changes in OA-fed birds indicated the kidneys and bursa of Fabricius as the primary organs to be affected by this toxin. Gross and microscopic changes due to S. Gallinarum infection indicated the liver and spleen as the primary organs affected by this infection. The effects of OA on the kidney and bursa of Fabricius were enhanced following S. Gallinarum infection. Degenerative changes and interstitial nephritis in the kidneys, and lymphocyte depletion from bursal follicles were more pronounced and were observed earlier in the combination group. In conclusion, data indicate that birds fed OA and infected with S. Gallinarum will demonstrate increased pathology compared with birds fed OA alone or those infected with S. Gallinarum but not fed OA.     

Immunogenic potential and protective efficacy of a sptP deletion mutant of Salmonella Enteritidis as a live vaccine for chickens against a lethal challenge

Salmonella Enteritidis (SE) is a highly adapted pathogen causing severe economic losses in the poultry industry worldwide. Chickens infected by SE are a major source of human food poisoning. Vaccination is an effective approach to control SE infections. This study evaluated the immunogenicity and protective efficacy of a SE sptP deletion mutant (C50336ΔsptP) as a live attenuated vaccine (LAV) candidate in chickens. 14 day-old specific pathogen-free (SPF) chickens were intramuscularly immunized with various doses of C50336ΔsptP. Several groups of chickens were challenged with the virulent wild-type SE strain Z-11 via the same route at 14 days post vaccination. Compared to the control group, the groups vaccinated with 1 × 10⁶, 1 × 10⁷ and 1 × 10⁸ colony-forming units (CFU) of C50336ΔsptP exhibited no clinical symptoms after immunization. Only slight pathological changes occurred in the organs of the 1 × 10⁹ CFU vaccinated group. C50336ΔsptP bacteria were cleared from the organs of immunized chickens within 14 days after vaccination. Lymphocyte proliferation and serum cytokine analyses indicated that significant cellular immune responses were induced after the vaccination of C50336ΔsptP. Compared to the control group, specific IgG antibody levels increased significantly in vaccinated chickens, and the levels increased markedly after the challenge. The 1 × 10⁷, 1 × 10⁸, and 1 × 10⁹ CFU vaccinated chickens groups showed no clinical symptoms or pathological changes, and no death after the lethal challenge. Whereas severe clinical signs of disease and pathological changes were observed in the control group chickens after the challenge. These results suggest that a single dose of C50336ΔsptP could be an effective LAV candidate to against SE infection in chickens.     

Study on immunofunction and immunoregulation post newcastle disease vaccination of chickens infected with chicken anemia virus

Study on immunofunction and immunoregulation post newcastle disease vaccination of chickens infected with chicken anemia virus     

Safety and efficacy of a virulence gene-deleted live vaccine candidate for fowl typhoid in young chickens

The safety and efficacy of a live lon-and-cpxR-deleted Salmonella enterica serovar Gallinarum (SG) vaccine candidate (JOL916) was evaluated in young layer chickens. Vaccinated (n=25) and unvaccinated (n=25) groups were organized, respectively, at 1, 2, 3, and 4 weeks of age. One-week-old and 2-week-old chickens were orally inoculated with 2×10⁷ colony-forming units of JOL916, and orally challenged with 2 x 10⁶ colony-forming units of a wild-type SG strain at the third week post vaccination (w.p.v.). Doses of vaccination and challenge were increased 10-fold for 3-week-old and 4-week-old chickens. SG-antigen-specific peripheral lymphocyte proliferation response and concentrations of plasma IgG and secretary IgA in the intestine were examined at the second w.p.v. Gross lesions of the liver and spleen and recovery of the vaccine strain from the spleen were also examined at the second w.p.v. No evidence of side effects was detected by observation of general condition and body weight gain in all vaccinated groups. No, or very mild, gross lesions in the chickens were observed in the liver and/or spleen after vaccination. Significant cellular immune responses and systemic IgG responses were induced after vaccination in all age groups. Elevation of secretary IgA concentration was significant in the group, vaccinated at the age of 1 week. Depression scores after challenge were significantly lower in the vaccinated groups, as compared with the corresponding control groups. Significant reductions of death rates were observed in all vaccinated groups, as compared with the equivalent unvaccinated groups. Thus, the oral vaccination of young chickens with JOL916 was demonstrated to be safe. Moreover, it offered efficient protection against fowl typhoid.     

Detection of intestinal intraepithelial lymphocytes,goblet cells and secretory IgA in the intestinal mucosa during Newcastle disease virus infection

Newcastle disease, which is caused by Newcastle disease virus (NDV), is a highly contagious viral disease of poultry and other bird species. The mucosa is the first line of defence to invading pathogens, including NDV, and it has been confirmed that the mucosa can contribute to host protection. This study was conducted to evaluate the intestinal mucosal immunology in NDV infection. Forty specific-pathogen-free chickens were divided into two groups, 20 birds in each group. Group 1 was inoculated with NDV by the intravenous route. Group 2 was used as the control group and was given sterile phosphate-buffered saline by the same route. At 24, 48, 72, and 96 h post infection (h.p.i.), five chickens from each treatment were killed. Samples of the duodenum, jejunum, and ileum were collected to quantify intestinal intraepithelial lymphocytes (IEL), goblet cells and secretory IgA (sIgA) by cytochemistry and immunohistochemistry analysis. The results indicated that IEL were increased from 24 to 72 h.p.i. in the infected tissues, and were significantly higher than in the control group at 48 h.p.i. (P < 0.01). In contrast to IEL, goblet cell numbers were reduced dramatically from 24 to 96 h.p.i. in the infected birds (P < 0.01) Furthermore, the content of sIgA was significantly higher at 48 and 72 h.p.i. in the infected tissues (P < 0.01). sIgA positivity was observed in the epithelial lining of the intestinal mucosa. These data suggest that IEL, goblet cells, and sIgA were involved in the intestinal mucosal immunity against NDV infection.     

Immune Responses against Salmonella enterica Serovar Enteritidis Infection in Virally Immunosuppressed Chickens

To understand the role of immune mechanisms in protecting chickens from Salmonella infections, we examined the immune responses of Salmonella enterica serovar Enteritidis-infected chickens and the effect of chicken anemia virus (CAV), a T-cell-targeted virus, on S. enterica serovar Enteritidis-induced immune responses. One-day-old chicks were orally inoculated with S. enterica serovar Enteritidis with or without intramuscular injection of CAV. The bacterial infection, pathology, and immune responses of chickens were evaluated at 14, 28, and 56 days postinoculation. The infection increased the levels of S. enterica serovar Enteritidis-specific mucosal immunoglobulin A (IgA), the number of gut-associated T cells, and the titer of serum IgG specific for S. enterica serovar Enteritidis surface antigens. CAV infection depressed these immune responses, especially the mucosal immune responses, but did not increase the number of S. enterica serovar Enteritidis-infected cells in the intestine. The severity of pathological lesions appeared to be reciprocal to the level of immune responses, but the S. enterica serovar Enteritidis infection persisted. These results suggest that oral infection of S. enterica serovar Enteritidis in chickens induces both mucosal and systemic immune responses, which have a limited effect on the S. enterica serovar Enteritidis infection under conditions designed to mimic the field situation.     

Pathology of the thymus,spleen and bursa of Fabricius in zinc-deficient ducklings

The weight and growth index of bursa of Fabricius, thymus and spleen were significantly reduced (P < 0.05 or P < 0.01) in zinc (Zn)-deficient ducks (Zn 22.9 mglkg diet) when compared with normal ducks. The G0/Gl phase of the cell cycle of the bursa of Fabricius, thymus and spleen was much higher, and the S and G2+M phases lower in Zn-deficient ducks than in the controls. Histopathologically, there was lymphocyte degeneration and depletion of lymphoid organs, and the reticular cells of thymus were also degenerate or necrotic in the Zndeficient group. The results demonstrated that Zn deficiency seriously inhibited the growth of lymphoid organs and caused marked pathology in the lymphoid organs. The results also showed that the effect of Zn deficiency on the primary lymphoid organs occurred earlier than on the secondary lymphoid organs. The effect of Zn deficiency was greatest on the bursa of Fabricius, followed by the thymus, and then the spleen.     

Time-course investigation of infection with a low virulent Pasteurella multocida strain in normal and immune-suppressed 12-week-old free-range chickens

Twelve-week-old indigenous chickens, either immune-suppressed using dexamethasone (IS) or non-immune-suppressed (NIS), were challenged with a low virulent strain, Pasteurella multocida strain NCTC 10322^T, and developed clinical signs and pathological lesions typical of chronic fowl cholera. NIS birds demonstrated much more severe signs of fowl cholera than IS birds. With few exceptions, signs recorded in IS and NIS birds were of the same types, but significantly milder in the IS birds, indicating that immune suppression does not change the course of infection but rather the severity of signs in fowl cholera. P. multocida signals by fluorescent in situ hybridization (FISH) were observed between 1 h and 14 days in the lungs, trachea, air sacs, liver, spleen, bursa of Fabricius and caecal tonsils, while signals from other organs mostly were observed after 24 h. More organs had FISH signals in NIS birds than in IS birds and at higher frequency per organ. Many organs were positive by FISH even 14 days post infection, and it is suggested that these organs may be likely places for long-term carriage of P. multocida following infection. The present study has demonstrated the spread of P. multocida in different tissues in chickens and distribution of lesions associated with chronic fowl cholera, and pointed to a decrease of pathology in IS birds. Since dexamethasone mostly affects heterophils, the study suggests that these cells play a role in the development of lesions associated with chronic fowl cholera in chickens.     

Influence of antigenic stimulation on lymphoid cell traffic in the chicken

The influence of one intravenous injection of human serum albumin (HSA) on the pattern of cell migration from the bursa of Fabricius was studied in six-week old chickens. The bursa was labeled in situ with ['Hlthymidine 24 h after either HSA o r saline administration. Forty-eight hours following local labeling of the bursa, the chickens were killed and the transport of label to other lymphoid organs studied with a radiochemical method, based on measurements of tritium in DNA of the different organs, and with autoradiography. The radiochemical method revealed a significantly increased proportion of bursa-derived label in the spleen of the immunized chickens. This was associated with an increased number of heavily labeled bursa-derived cells in the autoradiograms from the same organ. The majority of the bursa emigrant cells in the spleen were localized in the red pulp, particularly in clusters of pyroninophilic cells. Their topographical distribution was not apparently influenced by the immunization. It is suggested that the increased homing of bursa-derived cells to the spleen may reflect a recruitment of antibody-forming cell precursors.     

Viral protein sythesis by tissues from avian leukosis virus-infected chickens. II. Effect of passive neutralizing antibody in normal and agammaglobulinaemic chickens.

Synthesis in vitro of avian leukosis virus (ALV) group (gs proteins, p27 and p12, by various tissues from chickens infected within a few days after hatching was studied by means of autoradiography of immunoelectrophoretic patterns. Viral protein was synthesized in all tissues of chicks examined between days 18 and 50 of age after which time liver, kidney, bursa, thymus, and spleen became negative. The lung and genital organs of the chicks, however, continued to synthesize viral protein up to 100 days of age, when the experiment was ended. Repeated injections of neutralizing chicken antibody to ALV (Ab) starting on day 26 or 37 caused gs protein to decrease in spleen, liver, and thymus within 5 days but not in bursa, lung, and genital organs. Agammaglobulinaemic (Agamma) chickens showed prolonged persistence of gs protein synthesis in the spleen and liver; this synthesis was abrogated by passive Ab. Liver from Agamma chickens, however, also became negative without Ab treatment. The relative roles of antibody and cellular immunity in influencing ALV replication during the initial phase of infection before lymphoma development are discussed.     

The effects of polymorphisms in IL-2, IFN-γ, TGF-β2, IgL,TLR-4, MD-2, and iNOS genes on resistance to Salmonella Enteritidis in indigenous chickens

Salmonella Enteritidis is a major cause of food poisoning worldwide, and poultry products are the main source of S. Enteritidis contamination for humans. Among the numerous strategies for disease control, improving genetic resistance to S. Enteritidis has been the most effective approach. We investigated the association between S. Enteritidis burden in the caecum, spleen, and liver of young indigenous chickens and seven candidate genes, selected on the basis of their critical roles in immunological functions. The genes included those encoding interleukin 2 (IL-2), interferon-γ (IFN-γ), transforming growth factor β2 (TGF-β2), immunoglobulin light chain (IgL), toll-like receptor 4 (TLR-4), myeloid differentiation protein 2 (MD-2), and inducible nitric oxide synthase (iNOS). Two Malaysian indigenous chicken breeds were used as sustainable genetic sources of alleles that are resistant to salmonellosis. The polymerase chain reaction restriction fragment-length polymorphism technique was used to genotype the candidate genes. Three different genotypes were observed in all of the candidate genes, except for MD-2. All of the candidate genes showed the Hardy–Weinberg equilibrium for the two populations. The IL-2-MnlI polymorphism was associated with S. Enteritidis burden in the caecum and spleen. The TGF-β2-RsaI, TLR-4-Sau 96I, and iNOS-AluI polymorphisms were associated with the caecum S. Enteritidis load. The other candidate genes were not associated with S. Enteritidis load in any organ. The results indicate that the IL-2, TGF-β2, TLR-4, and iNOS genes are potential candidates for use in selection programmes for increasing genetic resistance against S. Enteritidis in Malaysian indigenous chickens.     

Evaluation of a selected lactic acid bacteria-based probiotic on Salmonella enterica serovar Enteritidis colonization and intestinal permeability in broiler chickens

Two experiments were conducted to evaluate the effect of a lactic acid bacteria-based probiotic (FloraMax-B11^®) against Salmonella enterica serovar Enteritidis intestinal colonization and intestinal permeability in broiler chickens. Experiment 1 consisted of two independent trials. In each trial, day-old broiler chicks were assigned to one of two groups: control?+?S. Enteritidis or probiotic?+?S. Enteritidis. At 72?h post-S. Enteritidis challenge, haematology and caecal content were evaluated for S. Enteritidis colonization. In Experiment 2, day-old broiler chicks were assigned to one of four groups: negative control; probiotic; control?+?S. Enteritidis; or probiotic?+?S. Enteritidis. At 72?h post-S. Enteritidis challenge, chickens in all groups were given an oral gavage dose of fluorescein isothiocyanate dextran (FITC-d). In both trials of Experiment 1, a significant reduction (P?S. Enteritidis in caecal content and a reduction in the incidence of S. Enteritidis enriched caecal samples were observed in probiotic?+?S. Enteritidis chickens. In addition, significant heterophilia and lymphopaenia were observed in control?+?S. Enteritidis chickens. In Experiment 2, a decrease in numbers of S. Enteritidis in caeca were observed in probiotic?+?S. Enteritidis chickens when compared to control?+?S. Enteritidis. Also, an increase in serum FITC-d concentration was detected in control?+?S. Enteritidis. These results suggest that early infection with S. Enteritidis can increase intestinal permeability, but the adverse effects can be prevented by the administration of the probiotic tested.     

Comparative natural killer cell activities of thymic, bursal, splenic and intestinal intraepithelial lymphocytes of chickens

The natural killer (NK) cell activities of spleen, thymus, bursa, peripheral blood and gut intraepithelial lymphocytes (IEL) from FP and SC chickens were investigated in 4-hr and 16-hr 51Cr release assays. Target cells were 4 different tumor cell lines derived from either an avian leukosis tumor transplant (LSCC-RP9, LSCC-RP12) or from Marek's disease lymphomas (MDCC-MSB-1, MCDD-CU36). Great variability in cytotoxic potential was observed among NK cells of different lymphoid organs. NK cell cytotoxicity varied depending upon the type of effector cells, type of target cells, the ratio of effector to target cells, and the age and genetic background of chickens. Substantial levels of NK cell activity were detected in spleen and gut IEL of SC chickens in a 4-hr assay. In contrast, the NK cytotoxicity in gut IEL of FP chickens was not detectable until 16 hr after incubation. The ranges of target cell specificity demonstrated by IEL, spleen, thymus and bursa NK cells were similar to one another and, in general, the level of cytotoxicity increased with incubation time. Thymus and bursa NK cell activity of both SC and FP chickens was not detectable in a 4-hr assay but substantial NK cell activity was demonstrated in a 16-hr assay. The results of the present study demonstrate that various lymphoid organs of chickens, such as spleen, thymus, bursa, and gut intraepithelium, contain subpopulations of cells that can mediate spontaneous cytotoxicity.