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This experiment was conducted to evaluate the combined effects of manganese-amino acid complex and arginine supplementation on the immune competence of broilers. On the day of hatch 640 male Cobb 500 broiler chicks assigned to two study groups (immune stimulate and non-stimulated). A 2 × 2 factorial arrangement of treatments was used with two manganese sources (MnSO4 or manganese-amino acid complex - MnAA) and two digestible Arg:Lys ratios (1.12 or 1.20). The treatments are: IM (80 ppm MnSO4); MnAA (40 ppm MnSO4 + 40 ppm MnAA); IM+Arg: 80 ppm MnSO4+ L-Arg (Arg:DigLys 1.20); MnAA+Arg: 40 ppm MnSO4 + 40 ppm MnAA + L-Arg (Arg:Lys 1.20). For treatments 1 and 2, the digestible Arg:Lys ratio was 1.12, considered normal for corn-soybean meal-based diets. Birds in the immune stimulated group received a dose of Salmonella Enteritidis vaccine. For growth performance and lymphoid organ development, no significant results were observed. Non-stimulated birds fed diets with Arg supplementation had higher percentage of mucosal T helper, T helper and T cytotoxic, compared to the normal Arg:Lys ratio (1.12). In the immune stimulated birds, broilers fed exclusive IM diet had a higher amount of T helper, T cytotoxic, activated T cytotoxic, and APC cells compared to broilers fed MnAA. The inorganic Mn diets, resulted in higher humoral antibody level (increased IgM levels) only when associated with supplementation of L-Arg. However, the use of an associated Mn source, could support high levels of IgM in commercial levels of Arg. No differences were observed to macrophage phagocytic activity analyses., (© 2018 Poultry Science Association Inc.)

This experiment was conducted to examine the effect of trace mineral sources on broiler performance, carcass composition, trace mineral digestibility, and tibia bone quality of broiler chickens. A total of 480 Ross 308 male day-old chicks were allocated to 24 pens and assigned to 4 dietary treatments in a completely randomized design. Treatments were as follows: inorganic (I) was basal diet supplemented with 750 g/t inorganic trace mineral premix; organic 1 (O1) and organic 2 (O2) was basal diet supplemented with 375 and 500 g/t organic yeast proteinate trace mineral premix respectively; and hydroxychloride (H) was basal diet supplemented with 1000 g/t salt encrusted trace mineral premix. On day 25, no differences in feed intake (FI), body weight gain (BWG), feed conversion ratio (FCR), or livability (LV) were observed between treatments (P > 0.05). On day 38 birds fed O1 and H had higher weight gain (P < 0.05) and lower FCR (P < 0.001) relative to I. Mineral sources had no impact on FI or LV (P > 0.05) on day 38. Spleen percentage of body weight on day 25 was increased in birds fed O1 and H treatments (P < 0.05) over the I treatment. Mineral sources had no effect on relative weights of thymus or bursa of Fabricius on day 25, or bone quality and carcass composition on day 39 (P > 0.05). Apparent digestibilities of Cu and Zn were greater in birds fed yeast proteinated trace minerals compared to other sources.

With the ongoing intensification of the poultry industry and the continuous need to control pathogens, there is a critical need to extend our understanding of the avian immune system and the role of nutritional interventions on development of immune competence in neonatal chicks. In this review, we will focus on the ontogeny of the lymphoid organs during embryonic life and the first 2 weeks post-hatch, and how early feeding practices improve heath and modulate the development and function of the immune system in young chicks. The evidence for the positive impact of the nutrition of breeder hens on embryonic development and on the survival and immunity of their chicks will also be outlined. Additionally, we will discuss the vital role of supplemental feeding either in ovo or immediately post-hatch in chick health and immunity and the importance of these approaches in ameliorating immune system functions of heat-stressed chicks. To conclude, we provide some perspectives on a number of key issues, concerning the mechanisms of nutritional modulation of immunity, that need to be addressed. A thorough investigation of these mechanisms may assist in the formulation of diets to improve the immunity and general health status., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The aim of the study was to examine the effects of cage furnishing and social stress on some lymphoid organ weight and innate, cell-mediated, and humoral immune responses in laying hens. Sixty-four chickens were used. The chickens were divided into 2 groups; one of the groups was reared in furnished cages (RFC) and the other was reared in conventional cages (RCC). In wk 17, social stress was applied. Heterophil and lymphocyte percentages; liver, spleen, thymus, and bursa of Fabricius weights; phagocytic activity; oxidative burst and chemotaxic activity of heterophil; CD4+ and CD8+ cell proportions; and antibody production were measured. The effect of rearing methods was significant on heterophil, lymphocyte percentage, heterophil/lymphocyte (H/L) ratio, and antibody production. Heterophil percentage and H/L ratio were lower (P=0.001, P=0.001, respectively), and antibody production was higher (P=0.003) in RFC hens compared to RCC hens. The main effect of social stress was also significant on heterophil, lymphocyte percentages, and H/L ratio. Heterophil percentage was higher (P=0.049); H/L ratio tended to be higher (P=0.068); and lymphocyte percentage tended to be lower (P=0.072) due to stress. In addition, thymus and bursa of Fabricius weights tended to be lower (P=0.073 and P=0.074, respectively) in stressed hens. There were significant interactions between rearing methods and social stress on oxidative burst, chemotaxic activity, and CD4+ and CD8+ proportion (P=0.001, P=0.004, P=0.054, and P=0.001, respectively). These parameters were significantly higher in RFC hens, when they were exposed to stress. On the other hand, they did not differ in RCC or unstressed RFC hens. These results indicated that cage furnishing positively affected heterophil functions, CD4+ and CD8+ cell proportions, and antibody production. Therefore, we suggest that cage furnishing, which is recommended for improving the welfare of animals, is also beneficial for improving the immune response of hens under the stress condition., (© 2015 Poultry Science Association Inc.)

Previously, the different monochromatic lights have been demonstrated to affect splenocyte proliferation and melatonin (MEL) secretion in broilers. The present study was designed to evaluate the effects of different monochromatic lights on the development and immune function of broiler cecal tonsils, and to disclose the mechanisms underlying these phenomena. A total of 185 broilers (P0) including intact, sham-operated, and pinealectomized groups were exposed to blue light (BL), green light (GL), red light (RL), and white light (WL) by a light-emitting diode system for 14 days. Compared with RL groups, the GL in the intact and sham-operated groups showed larger follicle areas (66.70%), higher percentages of proliferating cell nuclear antigen (PCNA)-positive cells (33.33%), increased numbers of IgA(+) cells (48.60%), and increased antioxidase activity (33.33%-61.37%), whereas, the density of iNOS and MDA content in GL were lower (43.63%-54.43%) than that of RL. In contrast, after pinealectomy, the area of follicles, the percentage of PCNA-positive cells, the number of IgA(+) cells, and the antioxidase activity decreased in the different light treatments, but the density of iNOS and MDA content increased substantially. There was no significant difference in these parameters between broilers exposed to GL and other lights (P = 0.085-1.000). The results suggested that the enhanced effects of GL on the development and immune function of cecal tonsils in young broilers were mediated by elevated antioxidative status via up-regulation of MEL., (© 2014 Wiley Periodicals, Inc.)

A total of 250 broilers in a completely randomized design selected to evaluate the effect of different levels of chromium (Cr) supplementation on performance, carcass traits and some blood parameters of heat-stressed broiler chicks. All birds were kept under heat stress temperature (33 ± 3°C) and divided into five treatments groups. Each treatment consisted of five pens with 10 birds in each pen. The basal diets were supplemented with 0 ppb (control), 800 ppb Cr-L-Met (T(1)), 1,200 ppb Cr-L-Met (T(2)) or 800 ppb CrCl(3) (T(3)), and 1,200 ppb CrCl(3) (T(4)). The feed intake and body mass were measured at 10, 21, and 42 days of age. Blood samples were collected from two birds in each replicates to determine biological and hematological values at 28 and 42 days of age. There were no significant difference in mass gain and feed conversion of broilers that received Cr supplementations compared with controls. The serum glucose concentration decreased in broilers received organic chromium methionine supplements compared with other treatments groups. Slight but not significant increases were observed in serum high-density lipoprotein (HDL) concentration of treated groups than controls while the mean serum HDL concentration was significantly higher in T(2) group compared with control group. Serum low-density lipoprotein level decreased in broiler received organic Cr supplements (p < 0.05).

Present paper reports the effects of aqueous and ethanolic extracts of sugar cane (Saccharum officinarum L.) juice and bagasse, respectively on protective immune responses in industrial broiler chickens against coccidiosis. Immunotherapeutic efficacies of the extracts were measured by evaluating their effect on body weight gain, oocyst shedding, lesion score, anti-coccidial indices, per cent protection and elicited serum antibody responses against coccidiosis. Results revealed a significantly lower (P<0.05) oocyst shedding and mortality in chickens administered with sugar cane extracts as compared to control. Further, significantly higher (P<0.05) body weight gains and antibody responses were detected in chickens administered with sugar cane extracts as compared to chickens of control group. Moreover, ethanolic extract showed higher anti-coccidia index (227.61) as compared to aqueous extract (192.32). The organ body weight ratio of the lymphoid organs of experimental and control groups were statistically non-significant (P>0.01). These results demonstrated that both ethanolic and aqueous extracts of sugar cane possess immune enhancing properties and their administration in chickens augments the protective immunity against coccidiosis., (Copyright © 2011 Elsevier Inc. All rights reserved.)

The chicken bursa of Fabricius and calf ileal Peyer's patch are thought to be the primary lymphoid organs of B cell development. In the bursa, the existence of secondary lymphoid tissue, called the diffusely infiltrated area, has been recognized. Recently, we have found the presence of a region of secondary lymphoid tissue in the ileal Peyer's patch at the period of the most rapid growth of this organ. In this study, we compared the development of these secondary lymphoid tissue regions in the bursa and ileal Peyer's patch histologically. Before hatching, lymphatic follicle formation occurred in the bursa, but not in the diffusely infiltrated area, where only a small number of lymphoid cells were found. However, during fetal calf development, lymphatic follicle formation occurred not only in the primary lymphoid organ but also in the secondary lymphoid tissue regions. Therefore, the prenatal development of the secondary lymphoid tissue regions of the bursa and ileal Peyer's patch were distinct. After hatching, formation of the germinal center, which contained many CD4+ cells, was observed in the diffusely infiltrated area of the bursa. After birth, many CD4+ cells and IgG mRNA expression were observed in the lymphatic follicle of the secondary lymphoid tissue regions in the ileal Peyer's patch, but rarely in the ileal Peyer's patch lymphatic follicles. The change of character of these secondary lymphoid tissue regions at the postnatal stage might be dependent on external antigens., (Copyright 2009 Elsevier B.V. All rights reserved.)

The CD1 molecules are cell-surface proteins that bind and present foreign lipids and glycolipids to T cells in a manner similar to the MHC system. While the mammalian CD1 antigen presentation pathway is well characterized, little is known about CD1 in non-mammalian vertebrates. Previous studies have identified two CD1 homologues in the chicken. We developed a monoclonal antibody designated NL1-1.A1 specific for the chCD1-1 isoform and have used this to characterize CD1 expression in tissues and cells of normal adult and embryonic chickens. The chCD1-1 isoform is expressed on a high proportion of cells in the spleen and bursa. Cells in the spleen that stain for CD1 are also positive for IgM and consistent with identification of these as B cells. In the skin, chCD1-1 is expressed on cells with dendritic morphology along the dermal-epidermal boundary and in epidermal sheets consistent with chicken Langerhans cells. Staining of cells in the medullary region of the chicken thymus was also observed. The CD1 proteins in mammals traffic to intracellular compartments to acquire lipid antigens for subsequent presentation to T cells on the surface. Consistent with data from mammal CD1 proteins, chCD1-1 partially co-localized with a lysosomal marker in the myeloid cell line BM2. Taken together, these data support broad distribution of chCD1-1 in both lymphoid and non-lymphoid tissues of the chicken that is remarkably similar to the distribution of CD1 isoforms in mammals.

Embryonic survival, pipping and hatching success, and sublethal biochemical, endocrine, and histological endpoints were examined in hatchling chickens (Gallus gallus), mallards (Anas platyrhynchos), and American kestrels (Falco sparverius) following air cell administration of a pentabrominated diphenyl ether (penta-BDE; DE-71) mixture (0.01-20 microg/g egg) or polychlorinated biphenyl (PCB) congener 126 (3,3',4,4',5-pentachlorobiphenyl; 0.002 microg/g egg). The penta-BDE decreased pipping and hatching success at concentrations of 10 and 20 microg/g egg in kestrels but had no effect on survival endpoints in chickens or mallards. Sublethal effects in hatchling chickens included ethoxyresorufin-O-dealkylase (EROD) induction and histological changes in the bursa, but these responses were not observed in other species. Polychlorinated biphenyl congener 126 (positive control) reduced survival endpoints in chicken and kestrel embryos and caused sublethal effects (EROD induction, reduced bursal mass and follicle size) in chickens. Mallards were clearly less sensitive than the other species to administered penta-BDE and PCB 126. In a second experiment, the absorption of penta-BDE (11.1 microg/g egg, air cell administered during early development) into the contents of chicken and kestrel eggs was determined at various intervals (24 h postinjection, midincubation, and pipping). By pipping, 29% of the penta-BDE administered dose was present in the egg contents in chickens, and 18% of the administered dose was present in kestrel egg contents. Based on uptake in kestrels, the lowest-observed-effect level on pipping and hatching success may be as low as 1.8 microg total penta-BDE/g egg, which approaches concentrations detected in eggs of free-ranging birds. Because some penta-BDE congeners are still increasing in the environment, the toxic effects observed in the present study are cause for concern in wildlife.

An experiment was conducted to determine the effects of different doses of liquid dl-2-hydroxy-4-methylthio butanoic acid (LMA) on growth performance and immune response in broiler chickens. In an arrangement with 4 graded levels of LMA to meet 80, 100, 120, and 140% of methionine requirements of broilers recommended by Chinese feeding standards for chickens, 256 one-day-old Arbor Acres male broiler chickens were randomly divided into 4 treatments with 8 replicates of 8 birds each. Growth performance, cellular immunity, and humoral immunity were determined. Results from increasing LMA levels were as follows. There were no significant differences (P > 0.05) in body weight gain and feed intake among the treatments, but the ratio of feed to gain was linearly decreased and significantly greatest (P < 0.05) in the group fed at 80% of methionine requirement. Serum globulin levels on d 21 and 42 were linearly increased significantly (P < 0.05); phagocytosis of neutral red of peripheral blood lymphocyte was quadratic and was lowest in the deficient group (P < 0.05). The proliferation of peripheral blood lymphocytes in response to lipopolysaccharide was quadratically influenced, and that of the 120% group on d 21 and the 100% group on d 42 was significantly greater than in the other groups (P < 0.05). Antibody titers to Newcastle disease virus on d 4 after the first inoculation of the vaccine were quadratically increased, anti-bovine serum albumin antibody production on d 13 after the second immunization was quadratic, and antibody titers were greatest in the groups fed at 100 or 120% of methionine requirement. In conclusion, methionine deficiency resulted in decreased feed utilization and decreased humoral and nonspecific immuno-competence of broiler chickens. The use of LMA to correct a methionine deficiency corrected these problems.

An experiment was conducted, including flow cytometry, to study the pathology of the lymphoid organs and peripheral blood T lymphocytes in zinc (Zn)-deficient chickens. One hundred 1-day-old broiler chickens were randomly divided into two groups and fed on diets with 100 mg/kg Zn (controls) or Zn-deficient diets (Zn, 23.63 mg/kg) for 7 weeks. The weight and growth index of the bursa of Fabricius, thymus and spleen were significantly reduced (P<0.05 or P<0.01) in Zn-deficient birds when compared with those of control broilers. The G0/G1 phase of the cell cycle of the bursa, thymus and spleen was much higher (P<0.01), and the S, G2+M phases and proliferating index lower (P<0.05 or P<0.01) in Zn-deficient broilers than in the controls. The acid alpha-naphthyl acetate esterase-positive ratio of the peripheral blood T lymphocytes and the CD4 and CD8 numbers were markedly reduced (P<0.05 or P<0.01), and the CD4/CD8 ratio increased. Histopathologically, lymphocytes of lymphoid organs were depleted and the reticular cells of the thymus were also degenerate or necrotic in the Zn-deficient birds. The results demonstrate that Zn deficiency seriously inhibited the development of lymphoid organs, impaired the progression of lymphocytes from the G0/G1 phase to the S phase, and caused pathological injury 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. Potential mechanisms underlying the observations are discussed.

A dietary deficiency of Arg may suppress chick immune system functions; however, research evaluating immune function responsiveness of commercial broilers fed dietary Arg levels near NRC (1994) recommendations is sparse. Therefore, three experiments were conducted to evaluate growth and immunity of broilers fed varying Arg levels near NRC (1994) specifications. Because Arg and Lys are similar in structure and are known to compete in intestinal absorption, dietary Lys treatments [near NRC (1994) recommendations] were evaluated to determine if Arg and Lys interact to affect broiler immunity. There were four dietary treatments in Experiment 1 representing a 2 x 2 factorial design of additional Arg (120% of NRC) or additional Lys (120% of NRC) added to a control diet containing 100% of NRC Arg and Lys (six replications per treatment). Experiment 2 contained the following four treatments: the control diet; the control diet plus L-Arg (0.20% Arg of diet); the control diet plus L-Lys HCl (0.20% Lys of diet); and the control diet plus L-Arg-L-Glu (0.10% Arg of diet). Graduations of Arg were fed from 90 to 120% of NRC in 10% increments in Experiment 3. Also, half of the birds were exposed to vaccinations of Newcastle disease virus and infectious bronchitis virus in Experiment 3 to derive a 2 x 4 factorial design. Experiments 1 and 2 were conducted from Days 1 to 18 and Experiment 3 was conducted from Days 1 to 15 in Petersime battery brooders. No interactions occurred between dietary Lys and Arg in Experiment 1. Increasing dietary Arg, but not Lys, from 100 to 120% of the NRC recommendation increased (P < or = 0.05) Day 18 BW gain. Treatment differences in the cutaneous basophil hypersensitivity assay in Experiment 1 did not occur. In Experiment 2, treatment differences in growth responses, lymphoid organ development, and primary antibody titers to SRBC did not occur. Unvaccinated birds in Experiment 3 fed an Arg-deficient diet had lower (P < or = 0.05) feed conversion in comparison with vaccinated birds fed an Arg-deficient diet. Vaccinated birds had lower (P < or = 0.05) Day 15 BW than unvaccinated birds, but higher (P < or = 0.05) titers to Newcastle disease virus. Increasing dietary Arg in Experiment 3 increased plasma Arg (P < or = 0.05), but did not affect plasma Lys. Although increased dietary Arg improved BW gain in Experiment 1, minimal effects were noted in growth and immune system parameters throughtout this study. A dietary Arg level near the NRC (1994) recommendation should support proper immune system functions in healthy chicks.

Continuous adrenocorticotropin (ACTH) delivery by mini-osmotic pumps is a reliable method to induce stress in broilers. The present study was conducted to determine the minimum effective dose of ACTH that will evoke physiological stress. Chicks, which had been reared under floor-pen conditions until 5 wk of age received mini-osmotic pumps by surgical implantation. The mini-osmotic pumps delivered 2, 4, 8, or 16 IU of porcine ACTH/kg BW/d for 7 consecutive d. Controls (CON) were untreated chicks. Continuous infusion of ACTH caused dose-related stress responses. Chicks that received 8 or 16 IU showed the greatest responses, whereas those that received 2 or 4 IU were intermediate to the birds dosed with high ACTH and the CON birds. Responses included decreased BW; decreased relative weights of the bursa of Fabricius, thymus, and spleen; and increased relative liver weight. Concomitantly, increased liver lipid and decreased liver moisture were recorded. Plasma concentrations of corticosterone (CS), glucose (GLU), total protein (TP), cholesterol (CHOL), and triglycerides (TRI) and the ratio of heterophils to lymphocytes were increased during ACTH infusion. ACTH infusion at 8 IU/kg BW/d for 7 d was determined to be the minimum effective dose that caused physiological stress in broilers.

A model was developed to study stress in chickens. Continuous administration of adrenocorticotropic hormone was employed (ACTH) using physiological mini-osmotic pumps. A validation of controls for this procedure showed that nonhandled (NHCON), sham surgical procedure for pump implantation (SMCON) and surgical implantation of a pump delivering saline (SALCON) were all acceptable controls. Continuous delivery of ACTH at 8 IU/kg BW/d for 7 d caused increases in plasma corticosterone (CS), glucose (GLU), cholesterol (CHOL), triglycerides (TRI), high-density lipoprotein (HDL), total protein (TP), and the heterophil/lymphocyte (H/L) ratio. Body weight, as well as relative weights of the major immunobiological organs (i.e., spleen, thymus, and bursa of Fabricius) were decreased. Finally, liver was increased due to lipid and moisture accumulation. This model is the first to show in a single experiment all the major adaptive stress responses of chickens.

In the chicken proventricular mucosa, aggregations of lymphocytes were localized in three different sites of the lamina propria, namely, underneath the surface epithelium, near the duct orifice of the deep proventricular gland, and in the gland tissue itself. In the lymphoid masses underneath the surface epithelium and in those near the duct orifice, CD4+ T lymphocytes and TCR2+ T lymphocytes occupied their central part, and B lymphocytes were localized in the periphery. CD8+ T lymphocytes and TCR1+ lymphocytes were evenly distributed in the masses. Infiltration of lymphocytes into these sites was first observed on the 20th embryonic day. At 1 week after hatching, CD3+ lymphocytes began to occupy the central area of the masses and His-C1+ B lymphocytes tended to be located in the periphery. Ultrastructurally, M cells were found neither in the epithelium of the mucosa nor in that of the excretory duct close to the lymphoid masses. In the deep proventricular gland, the lymphoid masses had a germinal center consisting of B lymphocytes, surrounded by the T lymphocyte-rich periphery. These masses were first recognized at the 3rd post-hatching week, presumably being formed against possible antigens invading into the lumen of the proventricular gland. On the other hand, the lymphoid masses beneath the surface epithelium and those near the duct orifice existing before the hatching period were considered to be prepared to establish the local mucosal immune barriers against the expectant antigenic invasion.

In vivo effects of graded dietary levels of arginine on the body and lymphoid organs were investigated using Cornell K strain chickens of the B15/B15 haplotype. Two-week-old birds were fed an arginine-deficient basal diet (0.53% arginine) supplemented with additional arginine (up to 1.0% L-arginine to the diet). At four weeks of age, body weight, lymphoid organ weight, and concentrations of amino acids in plasma were measured. Arginine supplementation produced significant increases in plasma arginine (from 200 nM in chicks fed the basal diet to 2,000 nM in chicks receiving the 1.5% arginine diet) and ornithine concentrations (from 17 nM in chicks fed the basal diet to 500 nM in chicks receiving the 1.5% arginine diet). The arginine-deficient diet reduced body weight gain (P < 0.0001) and thymus, spleen, and bursa of Fabricius weights (P < 0.05). In contrast to the bursa weight, the thymus and spleen weights, as percentages of body weight, were also decreased (P < 0.05). This study suggests that arginine markedly influences lymphoid organ development, with a more pronounced effect on the thymus and spleen than on the bursa of Fabricius.

Background: We have analyzed by electron microscopy, immunohistochemistry, and flow cytometry the development of chicken caecal tonsil, the largest lymphoid organ of avian gut-associated lymphoid tissue (GALT)., Methods: White Leghorn chickens of different ages obtained from a local supplier were routinely processed by transmission electron microscopy. For both immunohistochemistry and flow cytometry, we tested a battery of specific monoclonal antibodies (mAbs) to chicken cell markers on caecal cryosections or cell suspensions, respectively., Results: A rudimentary caecal tonsil occurs at the end of incubation. The organ grows just after birth, reaching the adult condition 4 days later. Firstly (4 days to 2 weeks), it contains predominantly T lymphocytes, principally TcR alphabeta+ and CD4+ cells, which occupy largely the named caecal diffuse lymphoid tissue. In adult tonsils (6-week-old chickens) however, B lymphocytes, mainly expressing either IgM or IgA, predominate. They occur in both the subepithelial zone and the germinal centers, in which there are also a few T cells. After 2 weeks the CD8+ lymphocytes gradually become more numerous than CD4+ cells. In the tonsillar epithelium CD8+TcRgammadelta+ T cells, CD8+TcRgammadelta-alphabeta-, presumably NK cells, and a few B lymphocytes are the main cell subpopulations., Conclusions: Chicken caecum grows fast after hatching. The diffuse lymphoid tissue largely contains TcR alphabeta CD4+ or CD8+ cells. CD8+ cells of caecal epithelium represent gammadelta T cells or NK cells. B lymphocytes which occur in the subepithelial zone, germinal centers, and, in few numbers, the caecal epithelium predominantly express either IgM or IgA.

In the present study, we characterized intra-epithelial leukocytes in the digestive tract of chickens during postnatal development. Their phenotype was characterized by monoclonal antibodies in cryostat sections and the numbers of the different cell-types were counted in the epithelium of the esophagus, proventriculus, duodenum, jejunum, cecum, and colon. All intra-epithelial leukocytes bore the leukocyte-common antigen CD45; 35% were T lymphocytes, and 50% bore a B-cell marker. However, no immunoglobulin-bearing cells were detected in the epithelium. Monocytes and macrophages were found only in the epithelium of the esophagus. A remaining population of non-B, non-T, non-monocyte cells (15%) was present in all parts of the digestive tract. The number of intra-epithelial leukocytes was greatest in the duodenum and jejunum, and decreased in the proximal part of the cecum and in the colon. Intra-epithelial leukocytes were only sporadically detected in the proventriculus. The total number of intra-epithelial leukocytes increased until 8 weeks after hatching and then decreased at 18 months. In the esophagus, the total number of intra-epithelial leukocytes changed little during aging. We found that the intra-epithelial leukocytes of chickens and rodents are distinct in that chicken intra-epithelial leukocytes comprise a cell population that bears a B-cell antigen but that lacks surface immunoglobulins.

The development of bronchus-associated lymphoid tissue (BALT) in conventionally reared broiler chickens of 1 day and 1, 2, 3, 4, 6, and 8 weeks of age was studied using light and electron microscopy (scanning and transmission). BALT in these chickens resembled other mucosa-associated lymphoid tissues (MALT) in that it was composed of an altered epithelium overlying a population of lymphocytes and contained potential antigen-presenting cells, such as macrophages and dendritic cells; high endothelial venules were also present. In contrast to other MALT, epithelial cells in chicken BALT were not of the M-cell type; i.e., they lacked large numbers of apical tubules and vesicles for specialized uptake of luminal antigens. There were age-related differences in size, number, and cellular composition of BALT nodules. Lymphoid nodules were progressively larger and more numerous with increasing age. Germinal centers were present in birds 2 weeks of age and older. BALT epithelium was primarily squamous and non-ciliated in 1-day and 1-week-old chicks, becoming progressively more columnar and ciliated in older chickens. Lymphocyte infiltration of the epithelium was extensive at 1 to 4 weeks of age; in older chickens, distinct epithelial and lymphocytic compartments were separated by connective tissue.

Development of the lymphoid cell compartment in bronchus-associated lymphoid tissue (BALT) of specific pathogen free chickens was examined. Specifically, B lymphocytes, T cell subsets (CD4 and CD8), and IgA-, IgG-, and IgM-producing plasma cells were labeled using immunocytochemical methods. Immunoglobulin-producing cells (IgPC) were quantitated, and comparisons of IgPC numbers were made among chickens of different ages, among immunoglobulin isotypes, and between lymphoid (BALT) and nonlymphoid (non-BALT) areas in the primary bronchus. At hatching, BALT was devoid of IgPC, but by 2 weeks of age cells producing IgA, IgG, and IgM were present. Initially, there were approximately equal numbers of IgA-, IgG-, and IgM-PC; after 2 weeks of age, however, IgG- and IgM-PC outnumbered IgA-PC. At all ages, IgPC were more numerous in non-BALT regions of the primary bronchus than in BALT regions. Small numbers of T and B lymphocytes were present in BALT from 1-day old chickens, but substantial populations of these cells were not seen until 1-2 weeks of age. T helper (CD4+) cells were found near B cell regions in BALT lymphoid nodules, while T cytotoxic/suppressor (CD8+) cells were more evenly distributed throughout the nodules and in the epithelium. B lymphocytes predominated in germinal centers and also overlapped CD4+ populations adjacent to germinal centers. Lymphocyte cell types needed to initiate and regulate immune responses are present in chicken BALT and may be involved in protecting poultry from respiratory pathogens.

The purpose of the present study was to measure the effect of dietary fat source on the fatty acid composition of immune cells in chickens. One-day-old female chicks were fed corn and soybean meal-based diets containing 7% of either lard, corn oil, canola oil, linseed oil (LO), or menhaden fish oil (FO). After being fed experimental diets for 3 to 4 wk, samples of serum, thymus glands, bursa of Fabricius glands, and splenocytes were collected. All samples were frozen and stored at -80 C until lipid analysis. Results indicate that the fatty acid composition of the sera and immune tissues of chickens reflected the fat in the diet. The relative content of long-chain polyunsaturated fatty acids varied considerably among immune tissues, with, from greatest to least, spleen, bursa, and thymus. The young chick demonstrated a substantial capacity to elongate and desaturate linoleic (C18:2n-6) and alpha-linolenic acids (C18:3n-3). Feeding chicks fats rich in n-3 fatty acids (e.g., LO or FO) decreased significantly (P less than .05) the level of arachidonic acid (C20:4n-6) present in the serum and immune tissues by 50 to 75%. The levels of eicosapentaenoic acid (EPA, C20:5n-3) and docosahexaenoic acid (DHA, C20:6n-3) were substantially increased (P less than .05) by FO and LO feeding. However, LO, which is rich in C18:3n-3, was generally only one-half to one-quarter as effective as FO in elevating EPA and DHA levels in immune tissues. The implications for these changes in serum and immune tissue fatty acid profiles are discussed briefly.

One-day-old White Leghorn male chicks were fed different levels of Thyrotropin Releasing Hormone (TRH) (1 and 5 ppm) or Triiodothyronine (T3) (.1 and 1 ppm) for an 8-wk period. In a second experiment, chicken growth hormone (cGH) (10 micrograms/kg of BW) was injected (iv) into different birds daily for 7 days starting at 7 wk of age. Different groups of birds received both T3 (.1 and 1 ppm) and cGH. Serum concentrations of thyroxine (T4), T3, and growth hormone (GH), lymphoid organ weights, total circulating white blood cells (WBC), and differential counts were measured following hormone treatments. It was found that T3, cGH, or a combination of both significantly lowered serum T4 concentrations. Triiodothyronine supplementation at 1 ppm, alone or with cGH significantly increased serum T3 concentrations. Chicken GH with T3 (.1 ppm) significantly increased serum GH concentrations. Thyrotropin releasing hormone supplementation did not affect serum concentrations of either T4, T3, or cGH. Relative bursa weights were greater in chicks that received T3 (1 ppm) or TRH (1 or 5 ppm) but not cGH. Relative spleen weights were enhanced in response to cGH alone or with T3 (1 ppm) but not TRH. Total WBC count was significantly increased in response to T3 (1 ppm). Supplementation of T3 (.1 or 1 ppm), TRH (1 ppm), and the combination of cGH and T3 (1 ppm) significantly increased the percentage of lymphocyte cell population. These results demonstrate the impact of feeding hormones on T3, T4, and cGH concentrations in the serum and suggest the involvement of the above hormones in the growth of lymphoid organs as well as the production of lymphocytes.

The ontogenic development of the bursa-dependent lymphoid tissue in the chicken has been studied using rabbit antisera specific for B lymphocyte sub-populations and two elements of the bursal microenvironment. The antigens investigated were: the chicken B lymphocyte antigen ( CBLA ); mature B lymphocyte antigen ( CMBLA ); a foetal-associated antigen ( CFAA ) present on embryonic haemopoietic cells and adult bone marrow and bursa cells; immunoglobulin (Ig) and IgG; a bursa-specific cortical reticulin fibre antigen ( CBRFA ); a gut-associated mucin antigen ( CGAMA ) present on bursal medullary reticular epithelial (REp) cells. The development of suspected precursor cells was examined using a rabbit antiserum specific for foetal spleen cells. The major finding was the interrelationship between developing B cells and the bursal microenvironment. The first CBLA - and CFAA -positive cells were detected in the bursa at day 8 of incubation but their precise localization was difficult to assess. In 12-15 day embryos, both these cells were found predominantly in the tunica-propria in close proximity to cells bearing the reticulin fibre antigen CBRFA . This close association between CBLA -, CFAA - and CBRFA determinants represents the earliest stages of B cell differentiation and mimics that found in the adult bursa cortex. By day 18, the majority of bursa cells expressed CBLA and Ig and were localized in the developing medullary follicles, the REp cells of which were CGAMA -positive, demonstrating a very early interaction between intestinal tract contents, bursal REp cells and B cell maturation. Around hatching some bursa cells showed a marked increase in the membrane expression of CBLA and Ig, and the simultaneous expression of CMBLA and IgG. These cells were present in medullary follicles; CBRFA was present on cortical reticulin fibres which provided a supporting framework for the more immature CFAA -positive cells.

The light and electron microscopic structure of the germinal center of chicken caecal tonsils were studied. Two kinds of germinal centers were revealed; the first was located deep in the lymphatic tissue close to the muscle layer of the caeca. These germinal centers frequently have an incomplete capsule, and are not, therefore, separated from the diffuse lymphatic tissue. The second kind of germinal center was located closer to the epithelium and had a complete capsule separating it from the diffuse lymphatic tissue. Both germinal centers possessed an outer dark cortical zone which contained smaller lymphoblasts (of less than 10 micron in diameter) and a central medullary area which contained larger lymphoblasts (up to 16 micron). Autoradiographic studies revealed that the small lymphoblasts of the outer cortical zone are concerned with cell generation and that the large lymphoblasts of the medullary area may have derived from the small lymphocytes. Within the medullary area of the germinal center are cells which are embedded in an intercellular substance of high density. We propose that the intercellular substance may be a product of this cell. For discussion purposes we have called this cell a secretory cell. The secretory cell may originate from a small lymphocyte-like cell.

Study was done of the distribution and relative densities of immunoglobulin (Ig)M-, IgG-, and IgA-producing cells in the gut-associated lymphoid tissues and the spleen (SP) of control and antibiotic-treated chickens between 3 and 28 days of age. Specific Ig in the serum also were quantitated simultaneously. Antibiotic treatment included preincubation dipping of fertile eggs in gentamicin solution (500 mg/L), injection of chicks with gentamicin (0.2 mg/chick, subcutaneously), and inclusion of chlortetracycline in the diet (200 mg/kg). At 3 days, the gut-associated lymphoid tissues of control chicks carried few Ig-positive cells, except the bursa of Fabricius in which all 3 classes of Ig-bearing cells were present in relatively large numbers. The SP had few,but equal, numbers of IgM- and IgA-positive cells at this age. As control birds grew older, IgM-positive cells dominated in the SP, followed by the IgA cells. Cell populations fluctuated in the bursa of Fabricius of chicks until 21 days of age when IgM and IgA cells stabilized at a higher density than the IgG-positive cells. The cecal tonsils had no Ig-positive cells at 3 days, mostly IgM cells by 7 days, but equal numbers of the 3 types of cells by 28 days. The large intestines had few IgM-positive cells at 3 days and no IgG cells at 3 or 7 days. The numbers of IgM and IgA cells were approximately equal in the large intestine of the chicks from 7 days until 28 days. Maternally acquired IgG predominated in sera of chicks until 14 days of age, followed by the IgM. At 28 days, 'there was more IgM in the serum than IgG. Serum IgA was not detectable until 14 days of age, and its concentration remained at a lower level than IgM or IgG values. Antibiotic-treated chickens generally carried lower densities of Ig cells than did the respective controls. However, statistically significant (P < 0.05) differences were apparent only with respect to Ig cell populations in the cecal tonsils and the large intestines. The treated chickens also had significantly lower serum IgM concentrations at 28 days of age.

The postnatal development of chicken mucosa-associated lymphoid tissues of the eyes, lungs, and intestines were investigated with monoclonal antibodies specific for either all leucocytes, B lymphocytes, mononuclear phagocytes, IgM, IgG, or IgA. Attention has been paid to the relation of lymphoid infiltrates with their surrounding mucosae, the segregation into B-cell and T-cell areas, development of germinal centers, and secretory immunoglobulins. Abundant secretory IgM and IgA was detected in the epithelium of the Harderian glands in the orbits, even though they lacked large leucocyte infiltrates with germinal centers. Lymphoid tissues in the mucosae of lungs and intestines developed separate B-cell and T-cell areas. The proventriculus, Meckel's diverticulum, and Peyer's patches generally contained germinal centers from 12 weeks of age on. Because chickens as young as 2 weeks old had germinal centers in bronchus-associated lymphoid tissue and cecal tonsils, these areas were probably highly stimulated by antigens. Isotype-specific monoclonal antibodies were used to detect IgM-, IgG-, and IgA-bearing follicular cells in the same germinal center.