The Postembryonic Development of the Immunological Barrier in the Chicken Spleens

Feeding Eucommia ulmoides extract enhances protection against high-temperature stress in chicks

Chick's susceptibility to heat stress often leads to growth retardation, immune function impairment, disease, and mortality. This thesis explores the potential ameliorative effect of 0.8% Eucommia ulmoides extract (EUE) into the diet of heat-stressed chicks in a 15-d feeding trial. The investigation reveals that feeding EUE significantly enhances the BW, ADG, AFI, and F/G of chicks experiencing heat stress. Additionally, the EUE groups exhibited higher levels of T-AOC (at 7 and 15d), SOD (at 15 d), GSH-Px (at 15 d), as well as lower MDA concentrations (at 7 and 15d) in chick serum. Pathological changes and H&E staining revealed that EUE effectively improved tissue damage in the duodenum, heart, and stomach induced by heat stress in the chicks. The EUE groups also showed higher levels of IgA (at 7 d), IgG and IgM (at 7 and 15 d). RNA-seq and WGCNA analysis revealed that EUE mitigates cellular damage and losses in heat-stressed chicks primarily through pathways involving signal transduction, protein synthesis and degradation, as well as cell cycle regulation, particularly the latter. This investigation serves as a fundamental and cognitive framework for the development and application of Eucommia ulmoides feed additives aimed at safeguarding the well-being of chicks in adverse environmental conditions.

Insights into microstructure and expression of markers of proliferation, apoptosis and T cells in the spleen of cattle egret (Bubulcus ibis)

The spleen is the largest secondary lymphoid organ with significant roles in pathogen clearance. It is involved in several avian diseases. The cattle egret is a wild insectivorous bird of agricultural and socioeconomic importance. Data related to microstructural features of cattle egret spleen are lacking. The present study investigated the gross anatomical, histological and immunohistochemical characteristics of the cattle egret spleen. Proliferation (PCNA and PHH3), apoptosis (cleaved caspase 3, C.CASP3) and T-cell (CD3 and CD8) markers were assessed. Grossly, the spleen appeared brownish red, oval-shaped and located at the oesophago-proventricular junction. Histologically, the spleen was surrounded by a thin capsule sending a number of trabeculae which contained branches of the splenic vessels. The white pulp consisted of the periarteriolar lymphoid sheath and periellipsoidal lymphatic sheath (PELS). The red pulp was formed of sinusoids and cords. The penicillar capillaries, which represent the terminal segments of the splenic arterial tree were highly branched, wrapped by prominent ellipsoids and directly connected to the splenic sinusoids, suggesting a closed type of circulation. Immunohistochemically, proliferating cell nuclear antigen (PCNA)-expressing cells were distributed with high counts throughout the splenic parenchyma, being highest within the splenic cords and PELS. Both PHH3- and C.CASP3-expressing cells revealed a similar pattern to that of PCNA, although with fewer counts. Large numbers of T cells were observed throughout the splenic parenchyma, mainly within the cords, as revealed by CD3 and CD8 immunoreaction. The present study provides a clear insight into the precise structure of the spleen in cattle egrets and thus improves our understanding about birds' immunity.

Selection for high and low antibody responses to sheep red blood cells influences cytokine and chemokine expression in chicken peripheral blood leukocytes and splenic tissue

White Leghorn chickens from a common founder population have been divergently selected for high (HAS) or low (LAS) antibody responses to sheep red blood cells (SRBC) for 49 generations resulting in 2 diverse lines for this trait. Much has been studied in these two lines; however, the impact of these selection pressures on cytokine and chemokine expression is not fully understood. The purpose of this study is to determine if selection for antibody response to SRBC impacts cytokine and chemokine expression in peripheral blood leukocytes (PBL) and spleen from HAS and LAS chickens. Total RNA was isolated from PBL and spleen after which mRNA expression of cytokines (IL4, IL6, IL10, TGF-β4) and chemokines (CXCL8, CCL4) were determined by quantitative real-time RT-PCR (qRT-PCR). The data were analyzed using Student's t test comparing HAS and LAS (P < 0.05) and are reported as corrected 40-CT. PBL and spleen samples were analyzed separately. With respect to PBL, expression of IL6 was higher (P < 0.05) in PBL isolated from LAS chickens compared to those from the HAS line whereas there were no differences (P > 0.05) in IL4, IL10, CXCL8, CCL4, or TGF-β4. The cytokine and chemokine mRNA expression profiles were different in the spleen between the two lines. IL4 and CXCL8 expression were higher (P < 0.05) in spleen samples from HAS chickens than LAS. The expression of IL6, IL10, CCL4, or TGF-β4 in the spleens did not differ (P > 0.05) between the lines. The data indicate that selection for specific antibody responses to SRBC impacts the cytokine and chemokine expression profile in PBL and spleens but in different ways in HAS and LAS. These studies provide insight into the influence that selection pressures for antibody responses have on different immune response components, specifically cytokines and chemokines typically involved in the innate response.

Dietary supplementation with pseudostellaria heterophylla polysaccharide enhanced immunity and changed mRNA expression of spleen in chicks

In recent years, increasing interest has focused on natural components extracted from plants, among which plant polysaccharides as natural immunomodulators that can promote animal immunity. The present study was performed to investigate the effect of feed supplement Pseudostellaria Heterophylla Polysaccharide (PHP) on serum Immunoglobulins, T lymphocyte subpopulations, Cytokines and Lysozyme (LZM) activity in chicks. In addition, the influence of PHP on splenic gene expression was investigated by transcriptome sequencing. Four hundred 7-day-old Gushi cocks were randomly divided into four groups in a completely randomized design. The chicks were fed with a basal diet supplemented with 0 (CON-A), 100 (PHP-L), 200 (PHP-M) and 400 (PHP-H) mg/kg PHP. Blood and spleen samples were collected from 6 randomly selected chicks in each group at 14, 21, 28, and 35 days of age. The results showed that compared to the CON-A group, the PHP-M group exhibited significant increases in the levels of IgA, IgG, IgM, CD3, and LZM in the serum at 14, 21, 28, and 35 days (P < 0.05), and at 28 d, there was a significant quadratic relationship between the levels of dietary PHP and the levels of IgG, IgM, IFN-γ, IL-2, CD3, and LZM. Furthermore, a total of 470 differentially expressed genes (DEGs) were identified in spleen from PHP-M and CON-A at 28 d. These DEGs were significantly enriched in the Phagosome, Intestinal immune network for IgA production and Cytokine-cytokine receptor interaction pathways. The present investigation highlights the ameliorating effect of dietary PHP on immunological variables and spleen of chicks, the study suggests that PHP supplementation can enhance immunity and positively impact spleen mRNA expression in chicks.

Spirulina platensis as a growth booster for broiler; Insights into their nutritional, molecular, immunohistopathological, and microbiota modulating effects

BACKGROUND

The present study is designed to assess the effect of adding various doses of Spirulina platensis (SP) on broiler chicken growth performance, gut health, antioxidant biomarkers, cecal microbiota, histopathology, and immunohistochemistry of inducible nitric oxide synthase (iNOS). 240 male Cobb 500 broiler chicks (1 day old) were placed into four groups (sixty birds/group), then each group was further divided into three replicates of 20 chickens each for 35 days. Birds were allocated as follows; the 1st group (G1), the control group, fed on basal diet, the 2nd group (G2): basal diet plus SP (0.1%), the 3rd group (G3): basal diet plus SP (0.3%), and the 4th group (G4): basal diet plus SP (0.5%).

RESULTS

Throughout the trial (d 1 to 35), SP fortification significantly increased body weight growth (BWG) and feed conversion rate (FCR) (P < 0.05). Bursa considerably increased among the immunological organs in the Spirulina-supplemented groups. Within SP-supplemented groups, there was a substantial increase in catalase activity, blood total antioxidant capacity, jejunal superoxide dismutase (SOD), and glutathione peroxidase (GPX) activity (P < 0.05). Fatty acid binding protein 2 (FABP2), one of the gut barrier health biomarkers, significantly increased in the SP-supplemented groups but the IL-1β gene did not significantly differ across the groups (P < 0.05). Different organs in the control group showed histopathological changes, while the SP-supplemented chicken showed fewer or no signs of these lesions. The control group had higher levels of iNOS expression in the gut than the SP-supplemented groups (p < 0.05). Cecal Lactobacillus count significantly elevated with increasing the rate of SP inclusion rate (p < 0.05).

CONCLUSION

Supplementing broiler diets with SP, particularly at 0.5%, can improve productivity and profitability by promoting weight increase, feed utilization, antioxidant status, immunity, and gastrointestinal health.

Cyto- and histoarchitectonics of the chicken spleen in the post-vaccination period

One of the main functions of the spleen is participation in many immunological processes, protecting the body from various harmful agents. It is a secondary organ of lymphopoiesis and the only organ of immunogenesis, which provides immune control of blood and detects genetically foreign agents in it, and performs the role of a biological filter. Therefore, the Study of its histo-architectonics has theoretical and practical significance. The histostructure of the spleen of chickens has significant differences, particularly the absence of trabeculae, a small amount of connective tissue based around large vessels. The structure of the spleen of one-day-old vaccinated and non-vaccinated chickens is not formed, as there is no differentiation of the white pulp from the red pulp, which is related to the biological features of the chickens' body. According to our research, the presence of lymphoid nodules is observed for the first time in the 25-day age of the vaccinated group chickens. According to morphometric studies, it was established that their number was 2.33 ± 0.42 pcs. Comprehensive farm vaccination programs include ten vaccinations of chickens up to 100 days of age. Under the influence of multiple antigenic stimulations in the following age periods of a 50-day-old bird (after six vaccinations: twice against infectious bronchitis and infectious bursal disease, once against Marek's disease and Newcastle disease), the 75-day (after nine times vaccination), 100-day (after ten times vaccination) number and sizes of lymphoid nodules, as well as periarterial lymphoid sheaths and periellipsoid lymphoid sheaths increased concerning chickens of the control group. Our research established that the histostructure of the spleen of one-day-old chickens of the experimental and control groups is incomplete. The bird's spleen, a peripheral organ of immune protection, is formed at 25 days. However, chickens are vaccinated twice (against Marek's disease and infectious bronchitis) in the incubator when they are less than one day old, and 90% of the planned vaccinations are completed by the age of 75 days. Therefore, studying morphological changes in the spleen of birds of different ages can be an essential tool for re-evaluating preventive treatment protocols in modern poultry farming.

Differential Replication and Cytokine Response between Vaccine and Very Virulent Marek's Disease Viruses in Spleens and Bursas during Latency and Reactivation

Marek's disease virus (MDV) infection results in Marek's disease (MD) in chickens, a lymphoproliferative and oncogenic deadly disease, leading to severe economic losses. The spleen and bursa are the most important lymphoid and major target organs for MDV replication. The immune response elicited by MDV replication in the spleen and bursa is critical for the formation of latent MDV infection and reactivation. However, the mechanism of the host immune response induced by MDV in these key lymphoid organs during the latent and reactivation infection phases is not well understood. In the study, we focused on the replication dynamics of a vaccine MDV strain MDV/CVI988 and a very virulent MDV strain MDV/RB1B in the spleen and bursa in the latent and reactivation infection phases (7-28 days post-inoculation [dpi]), as well as the expression of some previously characterized immune-related molecules. The results showed that the replication ability of MDV/RB1B was significantly stronger than that of MDV/CVI988 within 28 days post-infection, and the replication levels of both MDV strains in the spleen were significantly higher than those in the bursa. During the latent and reactivation phase of MDV infection (7-28 dpi), the transcriptional upregulation of chicken IL-1β, IL6, IL-8L1 IFN-γ and PML in the spleen and bursa induced by MDV/RB1B infection was overall stronger than that of MDV/CVI988. However, compared to MDV/RB1Binfection, MDV/CVI988 infection resulted in a more effective transcriptional activation of CCL4 in the latent infection phase (7-14 dpi), which may be a characteristic distinguishing MDV vaccine strain from the very virulent strain.

Short communication: Ex-situ conservation in hatcheries is associated with spleen development in Lepidochelys olivacea turtle hatchlings

Ex-situ conservation in hatcheries is a successful strategy for the recovery of sea turtle populations. However, it alters the ontogenesis of the brain and gonads, as well as body size and locomotor performance at nest emergence. Relocation to hatcheries may alter immune system development, since this depends highly on the nest environment. We hypothesized that ex-situ brooding would negatively associate with immune traits of Lepidochelys olivacea. Splenic cytoarchitecture and leukocyte quantification were used as proxies for the immune configuration. Body size, gonadal sex and sand temperature during incubation were determined. Additionally, the success of nest hatching and emergence was quantified. Linear mixed models of splenic cytoarchitecture, leucocyte proportions and body size, using sex and nest type as explanatory variables, evaluated the effects of ex-situ brooding. Generalized linear mixed models using quasibinomial distributions (log link) analyzed effects on hatching and emergence success. Hatchlings from ex-situ nests were heavier, larger and showed a greater spleen-somatic index. They showed more and better defined splenic periarteriolar lymphoid sheaths, as well as a higher proportion of heterophils but less monocytes. Moreover, ex-situ brooding increased hatching and emergence success. Sand temperatures in hatcheries favored male sex determination, while the opposite occurred for in-situ incubation. Interestingly, the immune configuration and body size were independent of sex but associated with ex-situ conservation. Greater body size promotes early hatchling survival, while better spleen development is related to a greater antibody production and a better immune response to pathogens. Altogether, the results suggest that ex-situ incubation is associated with a better immune configuration and higher survival success.

Immune parameters in two different laying hen strains during five production periods

During life, the number and function of immune cells change with potential consequences for immunocompetence of an organism. In laying hens, studies have primarily focused on early development of immune competence and only few have investigated systemic and lymphatic distribution of leukocyte subsets during adolescence and the egg-laying period. The present study determined the number of various leukocyte types in blood, spleen, and cecal tonsils of 10 Lohmann Brown-Classic and 10 Lohmann LSL-Classic hens per wk of life 9/10, 15/16, 23/24, 29/30, and 59/60, encompassing important production as well as developmental stages, by flow cytometry. Although immune traits differed between the 2 hen strains, identical patterns of age-related immunological changes were found. The numbers of all investigated lymphocyte types in the spleen as well as the numbers of blood γδ T cells increased from wk 9/10 to 15/16. This suggests an ongoing release of lymphocytes from primary lymphoid tissues and an influx of blood lymphocytes into the spleen due to novel pathogen encounters during adolescence. A strong decrease in the number of CTL and γδ T cells and an increase in innate immune cells within blood and spleen were found between wk of life 15/16 and 23/24, covering the transition phase to egg-laying activity. Numbers of peripheral and splenic lymphocytes remained low during the egg-laying period or even further decreased, for example blood CD4⁺ T cells and splenic γδ T cells. Functional assessments showed that in vitro IFN-γ production of mitogen-stimulated splenocytes was lower in wk 60. Taken together, egg-laying activity seems to alter the immune system toward a more pronounced humoral and innate immune response, with probable consequences for the immunocompetence and thus for productivity, health and welfare of the hens.

Early Nutrition with Different Diets Composition versus Fasting on Immunity-Related Gene Expression and Histomorphology of Digestive and Lymphoid Organs of Layer-Type Chicks

Simple Summary

With the continuous improvement in the progress of poultry industry, a better understanding of the avian immune system is necessary. A prolonged holding period (36–72 h), along with a delay in access to feed and/or water post-hatching, has a negative influence on performance, intestinal histomorphology, and the immune system development of chicks. Therefore, the present study aimed to investigate the effect of early feeding with different diet composition or delayed feeding during the first 72 h of chick’s life on the expression of immunity-related genes and histomorphology of digestive and lymphoid organs of layer-type chicks. Early nutrition post-hatching had no negative effect on the development of the lymphoid and digestive organs in chicks. Histomorphological examination revealed an increase in cortex and cortex:medulla of thymus and bursa in the early fed groups compared to the fasted ones, with resultant impacts on the primary lymphoid organs. Higher germinal center areas and white pulp of the spleen were recorded in the early fed chicks, implying augmented proliferation and maturation of B cells in the secondary lymphoid organs. In the liver, a strong positive reaction to Best’s carmine stain in the early fed groups, indicating that the liver of these chicks had numerous glycogen granules in the cytoplasm of hepatocytes. The expression levels of splenic-immunity related genes were up-regulated in most of the early fed chicks at 14 day of age. Our findings suggested that early feeding post-hatch can modify the splenic-immunity related genes and modulate the histomorphology of the digestive (liver and proventriculus) and lymphoid organ in layer-type chicks during the early life post-hatching.

Abstract

Early feeding post-hatching (EFPH) can impact the immune response and modify the immunity-related gene expression. Therefore, we aimed to examine the effects of EFPH with different diets composition versus fasting during the first 72 h of chick’s life on the histomorphological structures of the liver, proventriculus, central and peripheral lymphoid organs, and immunity-related genes in layer-type chicks during the brooding period. A total of 400 chicks were randomly allotted into 4 groups with 4 replicates each. The experimental groups during the first 72 h of life were: feed and water deprivation (control, T1), feeding a starter layer diet (20% CP and 11.84 MJ/kg ME, T2), feeding a starter layer diet contained 3% molasses in its composition (20% CP and 11.81 MJ/kg ME; T3), and feeding a starter broiler diet (23% CP and 12.68 MJ/kg ME, T4). After the first 72 h of chick’s life, all chicks were fed ad libitum the T2 diet. EFPH had no negative effect on the development of the lymphoid or digestive organs in chicks. Greater relative weights of the spleen and bursa of Fabricius (p < 0.05) were observed in the early fed chicks compared to control at day 14 of age. Histomorphological examination revealed an increase (p < 0.05) in thymus cortex and cortex:medulla in the T3 and T4 groups compared to the fasted ones at day 28 of age. Pelicae height, follicular width, cortex, and cortex:medulla of bursa were improved (p < 0.01) in the fed groups compared to fasted chicks, with resultant influences on the primary lymphoid organs. Compared to control, higher germinal center areas and white pulp of the spleen (p < 0.05) were recorded in the early fed chicks, implying augmented proliferation and maturation of B cells in the secondary lymphoid organs. In the liver, a strong positive reaction to Best’s carmine stain in the early fed groups, indicating that the liver of these chicks had numerous glycogen granules or greater glycogen density in the cytoplasm of hepatocytes. There was a significant enhancement in the proventriculus mucosal and gland thickness, as well as fold height (p < 0.05) in the early fed chicks. The expression levels of splenic Toll-like receptor 2, interleukin 4, tumor necrosis factor α, and interferon gamma were up-regulated (p < 0.01) in most of the early fed chicks (T2, T3, and T4) compared to fasted ones at 14 day of age. In conclusion, EFPH could modify the splenic-immunity related genes and modulate the histomorphology of the digestive (liver and proventriculus) and lymphoid organs in layer-type chicks during the brooding period.

Different kinetics of chicken interferon-alpha signalling transduction responses following immunization of broiler chickens with different Newcastle disease virus vaccines and infection with virulent genotype VIId strain

Newcastle disease virus (NDV) is a highly contagious and notifiable avian disease leading to grave economic losses in the poultry industry. Although the immune responses against NDV have been widely investigated, little is known regarding the virus interaction with the host innate immune responses. In this study, we tested the effect of different commercially applied Newcastle disease vaccines as well as virulent NDV genotype VIId on the expression pattern of the upstream regulator and downstream effector genes related to chicken interferon-alpha (chIFNα) signalling transduction pathway. Using quantitative real-time PCR analysis, mild transient induction of chIFNα-inducible genes was detected in bird spleen 72 h post-vaccination (hpv) with either live LaSota (respiratory) or VG/GA (enteric) strains. Vaccination with the enteric VG/GA strain led to stimulation of the investigated pathway as early as 24 hpv which continued up to 7 days in bird caecal tonsils. Subcutaneous injection with inactivated LaSota oil adjuvant-based vaccine led to continual stimulation of the investigated pathway up to 7 days post-vaccination (dpv). The recombinant herpesvirus of turkey (rHVT) - NDV vaccine led to remarkable stimulation of all the tested cytokines up to 17 dpv in comparison with LaSota and VG/GA NDV vaccines. Stronger but transient activation of all the tested cytokines was detected in spleens during the first 24 h post-challenge with virulent NDV (vNDV) which reduced gradually and diminished later due to the virus-induced lymphocytic depletion. This study will aid in the discovery of new approaches to control NDV.

Impact of Housing Environment on the Immune System in Chickens: A Review

During their lifespan, chickens are confronted with a wide range of acute and chronic stressors in their housing environment that may threaten their welfare and health by modulating the immune system. Especially chronic stressful conditions can exceed the individual's allostatic load, with negative consequences for immunity. A fully functional immune system is mandatory for health and welfare and, consequently, also for high productivity and safe animal products. This review provides a comprehensive overview of the impact of housing form, light regime as well as aerial ammonia and hydrogen sulfide concentrations on the immune system in chickens. Certain housing conditions are clearly associated with immunological alterations which potentially impair the success of vaccinations or affect disease susceptibility. Such poor conditions counteract sustainable poultry production. This review also outlines current knowledge gaps and provides recommendations for future research.

Morphological characterization of postembryonic development of blood-spleen barrier in duck

The spleen is the largest peripheral lymphoid organ and an important site of immune response, in which the blood–spleen barrier (BSB) plays a significant role to resist various pathogens. The BSB structure of duck spleen is different from that of chicken and mammals. However, no information about the development of BSB after the postembryonic age has been reported in ducks. The current study observed the spleen of 1, 7, 14, 21, 35, and 60-day-old ducks by light and electron microscopy to analyze the cellular structural development. The results showed that the spleen index was continuously increased from 1 to 14-day-old ducks. During their early age, the spleen of ducks showed no definite zone of white and red pulp, but the area of the white pulp was large compared to that of the red pulp. The diameter of the ellipsoid was constantly increased in up to 35-day-old duck spleen, while the periellipsoidal lymphatic sheath (PELS) and periarterial lymphatic sheath continuously developed after 1 D. The reticular fibers developed with age; their branching reached the ellipsoidal wall to show a developed framework in the BSB of 14-day-old ducks. After 7 D, the endothelial cells of the sheathed capillary showed a typical cuboidal shape; between these cells, the gaps increased as age advanced, while the thickness of the basement membrane and collagen fibers increased in 35-day-old ducks. The mechanical filtration function of BSB by intravenous injection showed a 1-layer ring of carbon particles restricted in the white pulp in 1-day-old duck spleen; however, in 14 to 60 D, these particles were restricted in the ellipsoid and PELS, forming 2-layer rings of carbon particles. Collectively, the cellular features of the duck BSB developed up to 35 D of postembryonic age to perform their immune function.