The Importance of the Bursa of Fabricius, B Cells and T Cells for the Pathogenesis of Marek’s Disease: A Review

Single-cell transcriptional profiling reveals cell type-specific responses to duck reovirus infection in the Bursa of Fabricius of Cairna moschata

Duck reovirus (DRV) is a universal waterfowl virus that causes significant economic losses in the duck industry. However, the role of the host innate immune response of the Bursa of Fabricius to DRV infection is largely unknown. In the present study, we constructed a single-cell resolution transcriptomic atlas of the Bursa of Fabricius of Cairna moschata after infection with HN10 (a novel DRV). Ten cell-type marker genes were used to annotate the cell type, indicating a high degree of cell heterogeneity in the Bursa of Fabricius. Most of the innate and adaptive immune system-related genes were highly expressed in T cells, B cells, neutrophils, macrophages, and DCs. In the Bursa of Fabricius, the proportions of DCs and macrophages were largely increased by HN10 infection at 14 d, suggesting that DCs and macrophages play important roles in the long-term viral response. Notably, a number of innate and adaptive immune system-related genes were highly expressed at 24 h after HN10 infection, indicating that the Bursa of Fabricius has a very strong immune function even in the early developmental stage. In the immune system, the NOD-like receptor signaling pathway and RIG-I-like receptor signaling pathway were significantly activated at the early stage of HN10 infection, while the Toll-like receptor signaling pathway was significantly activated at the late stage. Enrichment analysis suggested that different immune signaling pathways play roles in specific developmental stages. Our data provide an opportunity to reveal the immune response to DRV infection at the single-cell level.

Monoclonal IgY antibodies: advancements and limitations for immunodiagnosis and immunotherapy applications

Due to their high specificity and scalability, Monoclonal IgY antibodies have emerged as a valuable alternative to traditional polyclonal IgY antibodies. This abstract provides an overview of the production and purification methods of monoclonal IgY antibodies, highlights their advantages over polyclonal IgY antibodies, and discusses their recent applications. Monoclonal recombinant IgY antibodies, in contrast to polyclonal IgY antibodies, offer several benefits. such as derived from a single B-cell clone, monoclonal antibodies exhibit superior specificity, ensuring consistent and reliable results. Furthermore, it explores the suitability of monoclonal IgY antibodies for low- and middle-income countries, considering their cost-effectiveness and accessibility. We also discussed future directions and challenges in using polyclonal IgY and monoclonal IgY antibodies. In conclusion, monoclonal IgY antibodies offer substantial advantages over polyclonal IgY antibodies regarding specificity, scalability, and consistent performance. Their recent applications in diagnostics, therapeutics, and research highlight their versatility.

Effects of Dietary Callicarpa nudiflora Aqueous Extract Supplementation on Growth Performance, Growth Hormone, Antioxidant and Immune Function, and Intestinal Health of Broilers

C. nudiflora is notably rich in flavonoids and phenylethanoid glycosides, making it a significant natural source of antioxidants. We examined the effects of C. nudiflora aqueous extract (CNE) on growth performance, antioxidant function, immunity, intestinal barrier function, nutrient transporters, and microbiota of broilers. A total of 360 one-day-old broilers were randomly assigned to four treatment groups: a basal diet with 0 (control, CON), 300 mg/kg (CNEL), 500 mg/kg (CNEM), and 700 mg/kg (CNEH) CNE for 42 days. CNEL and CNEM groups quadratically increased body weight and average daily gain but decreased feed-to-gain ratios during the starter and whole phases. Regarding the immune response of broilers, CNE treatment linearly down-regulated jejunal myeloid differentiation factor 88 (MyD88) expression and interleukin-1β (IL-1β) and interferon-γ expression in the liver (d 21), while decreasing jejunal IL-1β expression and the concentration of serum tumor necrosis factor-α and interleukin-6 (d 42). The CNEM and CNEH groups had lower MyD88 and nuclear factor kappa B expression in the liver (d 21) compared to the CON group. Broilers in the CNEL and CNEM groups had higher spleen index and thymus index (d 21) and interleukin-10 expression from the liver and jejunal mucosa (d 42) than that in the CON group. For the antioxidant capacity of broilers, CNE treatment linearly decreased the content of malonaldehyde and increased the activity of total antioxidant capacity in serum (d 42). CNEM and CNEH groups linearly increased the activity of superoxide dismutase in serum and heme oxygenase-1 expression in the liver, while increasing the activity of glutathione peroxidase in serum, jejunal nuclear factor E2-related factor 2 expression, and NAD(P)H quinone oxidoreductase 1 expression in the liver (d 42). As for the growth hormone of broilers, CNEM group increased the level of serum insulin-like growth factor 1 and up-regulated jejunal glucagon-like peptide 2 (GLP-2) expression (d 21). Broilers in the CNEM and CNEH groups had higher jejunal GLP-2 expression and growth hormone (GH) expression in the liver and the level of serum GH (d 42) than that in the CON group. Additionally, the villus height and jejunal Occludin and Claudin-1 expression in the CNEM group increased. CNE-containing diets resulted in a linear increase in the expression of jejunal zonula occluden-1 (d 21), villus height to crypt depth ratio, jejunal Occludin, excitatory amino acid transporters-3, and peptide-transporter 1 (d 42). The regulation of Oscillospira, Ruminococcaceae_Ruminococcus, and Butyricicoccus genera indicated that CNEH altered the composition of the cecal microbiota. In general, supplementing broilers with C. nudiflora aqueous extract could boost hormones, immune and antioxidant function, and gut health, improving their growth performance. Hence, CNE was a promising poultry feed additive, with 500 mg/kg appearing to be the optimal dose.

In ovo feeding of probiotic lactobacilli differentially alters expression of genes involved in the development and immunological maturation of bursa of Fabricius in pre-hatched chicks

Compelling evidence indicates that immunological maturation of the gut-associated lymphoid tissues, including the bursa of Fabricius, is dependent upon antigenic stimulation post-hatch. In view of these data, the present study investigated the impact of exposing the immune system of chick embryos to antigenic stimuli, via in ovo delivery of poultry-specific lactobacilli, on the expression of genes associated with early bursal development and maturation. Broiler line embryonated eggs were inoculated with 106 and 107 colony-forming units (CFUs) of an individual or a mixture of Lactobacillus species, including L. crispatus (C25), L. animalis (P38), L. acidophilus (P42), and L. reuteri (P43), at embryonic day 18 (ED18). The bursa of Fabricius was collected from pre-hatched chicks (ED20) to measure the expression levels of various immune system genes. The results revealed that L. acidophilus and the mixture of Lactobacillus species at the dose of 106 CFU consistently elicited higher expression of genes responsible for B cell development, differentiation, and survival (B cell activating factor (BAFF), BAFF-receptor (BAFF-R)), and antibody production (interleukin (IL)-10) and diversification (TGF-β). Similar expression patterns were also noted in T helper (Th) cell-associated cytokine genes, including Th1-type cytokines (interferon (IFN)-γ and IL-12p40), Th2-type cytokines (IL-4 and IL-13) and Th17 cytokine (IL-17). Overall, these results suggest that the supplementation of poultry-specific lactobacilli to chick embryos might be beneficial for accelerating the development and immunological maturation of the bursa of Fabricius. However, further studies are required to determine if the changes in gene expression are associated with the developmental trajectory and phenotypes of bursal cells.

Distribution and developmental changes of IL-21 immunopositive cells in the bursa of Fabricius of Jinhu silky chicken

Bursa of Fabricius (BOF) is a unique immune organ of birds. It is the place where lymphocytes develop, differentiate and mature. Young chicken BOF is susceptible to infection and damage, and even atrophy, causing immune suppression, and bringing huge economic losses to chicken production. Therefore, studying the regulatory mechanism of chicken bursa development is of great practical significance for disease prevention and diagnosis. Jinhu silky chicken (JSC) is a local excellent breed in the Fujian Province of China and with strong disease resistance. However, studies on the disease resistance of JSC are scarce. This study aimed to provide a theoretical basis for reproduction and disease control of JSC. Developmental features of the structure and the IL-21-positive cell (IL-21 PC) distribution on the BOF in JSC were measured from 7 to 300 days of age. Bursas of chicken (n = 36) were taken at 7, 35, 70, 150, 240, and 300 days of age for preparation of paraffin sections and stained with hematoxylin-eosin (HE) and immunohistochemistry. The microstructure of JSC's BOF was similar to that of other poultry. The cortical-medullary boundary of the bursa nodule was not obvious at 7 days of age, but it was evident after 35 days of age. Before 70 days of age, IL-21 positive cells (PC) were scattered on the BOF. At 150 days of age, the number of IL-21 PC in the bursa were the highest and the nuclei were clear. The level of IL-21 PC gradually decreased with age. The BOF degenerated and disappeared in 300-day-old JSC. The histological structure of the BOF was similar to that of other poultry. IL-21 PC were widespread in the BOF at different ages, but the numbers were different.