Cellular composition of the bone marrow in the chicken. I. identification of cells

Incorporation of Fe⁵⁵ in vivo was used for verifying on radioautographs the identity of chicken bone marrow cells that are in the process of heme syntheses. Under the experimental conditions all labeled cells may be considered to be linked with erythroid differentiation. They were classified into five maturational stages according to their morphology and capacity for DNA synthesis. Granulocytes were identified by the presence of specific granules. All mononuclear cells were classified as lymphocytes which had a pachychromatic nucleus, a high nucleocytoplasmic ratio, lacked the capacity for DNA synthesis, and resembled small lymphocytes of the bursa, spleen and bone marrow that bound, in vitro, anti-chicken gamma globulins labeled with I¹²⁵. Radioautography with H³TdR was used to identify proliferating and non-proliferating members of each cell population. With the use of the morphological criteria thus established, reproducible differential counts could be performed on chicken bone marrow smears also in the absence of specific labeling. In normal, 3, 4, and 8 week old White Leghorn chicks, such counts revealed the bone marrow as a member of the lymphomyeloid complex preferentially adapted to the production and maturation of erythroid cells, while the reserve of granulocytes was found to be small compared to that of mammalian marrow. The percentage of lymphocytes appears to increase with age but, in contrast to rodent marrow, a proliferating precursor cell pool for lymphocytes could not be identified in chicken marrow up to the age of eight weeks.     

Purine metabolism and B-lymphocyte development in the chicken bursa of fabricius.

The activity of three enzymes involved in the salvage pathway of purine nucleosides--purine nucleoside phosphorylase (PNP), xanthine dehydrogenase (XDH), and hypoxanthine-guanine phosphoribosyl transferase (HGPRT)--was investigated in cellular fractions of the chicken bursa of Fabricius differentially enriched in epithelial cells or lymphocytes. Markedly increasing levels of PNP and XDH were observed along with the enrichment in epithelial cells together with a slight, though significant, decrease in HGPRT activity. By contrast, a dramatic fall in PNP and XDH activities was detected along with the enrichment in lymphocytes together with a slight, though significant, increase in HGPRT activity. This sharply different distribution of the three enzymes, all sharing hypoxanthine as a substrate, clearly indicates that lymphocytes preferentially channel hypoxanthine into the salvage and interconversion pathways, phosphorylating it to IMP, while epithelial cells rapidly catabolize such a purine base to uric acid. Moreover, epithelial cells, unlike lymphocytes, are able to retain high intracellular levels of both hypoxanthine and inosine. These results support the possibility that epithelial cells contribute to the normal development of bursal lymphocytes by supplying such actively proliferating cells with purine rings and at the same time by preventing them from accumulating potentially toxic high levels of purine nucleotides being able to rapidly eliminate excess hypoxanthine as uric acid from the bursa environment into the bloodstream.     

Cellular composition of the bone marrow in the chicken. I. Identification of cells.

Incorporation of Fe55 in vivo was used for verifying on radioautographs the identity of chicken bone marrow cells that are in the process of hemesyntheses. Under the experimental conditions all labeled cells may be considered to be linked with erythroid differentiation. They were classified into five maturational stages according to their morphology and capacity for DNA synthesis. Granulocytes were identified by the presence of specific granules. All mononuclear cells were classified as lymphocytes which had a pachychromatic nucleus, a high nucleocytoplasmic ratio, lacked the capacity for DNA synthesis, and resembled small lymphocytes of the bursa, spleen and bone marrow that bound, in vitro, anti-chicken gamma globulins labeled with I125. Radioautography with H3TdR was used to identify proliferating and non-proliferating members of each cell population.     

T-dependent areas in the chicken bursa of fabricius: An immunohistological study

Background: The so-called diffusely infiltrated lymphoid tissue of the chicken bursa of Fabricius was previously described as a T-dependent bursal area. Methods: We have analyzed immunohistologically its postnatal development by using a battery of mAbs, most of them raised specifically to chicken T cells, in order to characterize phenotypically the nature of its cell components, appearance, development, and possible functional significance. Results: Our results demonstrate that this tissue represents poorly developed lymphoid aggregates, the cell content reminiscent of that found in other lymphoid tissues occurring throughout the avian gut. The first lymphoid elements appear in this bursal area only after hatchin, growing rapidly to reach the adult condition in the second week of postnatal life. They consist mainly of T lymphocytes, including principally CD4⁺ TcRαVβ1⁺ cells, which form cell groups and CD8⁺ cells, and TcRγδ⁺ lymphocytes, which predominate in the subepithelial area and within the epithelium. MHC Class II molecule-expressing cells and IgM-, IgG-, and IgA-positive B lymphocytes also occupy the subepithelial region. Conclusions: We propose that the bursal diffusely infiltrated lymphoid tissue of the chicken represents gut-associated lymphoid tissue involved in mounting immune responses to antigens that reach the bursal lumen via the cloaca. © 1995 Wiley-Liss, Inc.     

Follicle-associated epithelium and medullary epithelial tissue of the bursa of fabricius are two different compartments.

The bursae of Fabricius from the chicken and turkey were studied by light and electron microscopy and immunohistochemical methods. The study focused on the relationship of follicle-associated epithelium to the medulla. The follicle-associated epithelium was supported by 3 to 5 layers of stratified epithelial cells which were a continuation of the corticomedullary epithelial cells. The follicle-associated epithelium consisted of M cells and scattered secretory dendritic cells. The network of the reticular epithelial cells of the medulla was filled with secretory dendritic cells, B cells, and a few T cells and macrophages. The cellular content of the follicle-associated epithelium and the medulla suggested that they were different cellular compartments. Communication between the follicle associated epithelium and medullary epithelial compartment occurred through the supporting cells of the follicle-associated epithelium. When the supporting layers of the follicle-associated epithelium infolded into the medulla, they formed lamellated epithelial bodies similar to the thymic Hassall bodies. The lamellated bodies enclosed secretory dendritic cells but not lymphocytes. The infolding of supporting cells varied from follicle to follicle. The asynchronization of infolding contributed to heterogeneity of follicle composition. Follicle heterogeneity was demonstrated by differences in reactivity with a battery of monoclonal antibodies.     

Apparent adoptive immune enhancement by bone marrow and bursa of fabricius cells from juvenile chickens

The occurrence of enhancer cells (EC) in the bone marrow and bursa of Fabricius of unprimed and mouse erythrocyte (MRBC) primed birds was investigated. EC are defined operationally as immunocompetent cells that are incapable of adoptive immunity in embryo hosts but able to enhance the immune responsiveness of newly-hatched chick recipients. Weak to moderate immune enhancement was observed in chick hosts grafted with bursal cells from unprimed or MRBC-primed donors whereas with bone marrow cell transfer the immune enhancement was weak with cells from unprimed donors but modest to strong with those from primed donors. Thus antigen priming of donors had little effect on the EC level of the bursa but appeared to increase that in the bone marrow. Moreover, the EC activity of bone marrow of primed donors was donorage dependent. Response profile studies revealed that the EC level of donor bone marrow was low the first 2–3 days after immunization and high by day six. The elevated EC level in the bone marrow of immunized donors is believed due to both recruitment of immigrant cells of extramedullary origin and clonal expansion of medullary immunocompetent cells.     

Cellular composition of rat bone marrow stroma. Antigen-defined subpopulations

Although stromal cells establish the architecture of mammalian bone marrow and organize hemopoiesis, the interrelationships among their macrophage, fibroblastic, endothelial, and adipocyte-like components are not wholly understood. Using murine monoclonal antibodies to cultured adherent cells of rat bone marrow, we observed that the predominant fibroblastoid cells grown from marrow differed from those of non-hemopoietic organs. The marrow type bore a detectable quantity of the ST3 but not ST4 antigen, whereas those from lung, diaphragm, and epididymal fat pad, bore more ST4 than ST3. Those from spleen were an equal mix of both types. Although the tissue distribution of the ST3 antigen was similar to that of Thy-1, it was not identical, and in the brain, the two structures were localized in different areas. While none of the ST3, ST4 (fibroblast directed), or BN(MB)35 (myeloid directed) antibodies recognized fat cells cultured from marrow, the ST10 antibody, selected for binding to marrow derived fat cells, stained peripheral adipose cells, unidentified aglobular cells in areas of fat cell formation, and macrophages, but not fibroblasts. On the basis of these observations, we suggest that the fibroblastoid cells of the marrow are different from those of non-hemopoietic tissues.     

Cryptosporidiosis of the bursa of fabricius and trachea in broilers

Cryptosporidial parasitisation of the bursa of Fabricius and trachea is described in broilers. The response in both tissues was of epithelial hyperplasia and inflammatory cell infiltration. No clinical signs were reported.     

Cellular composition of the spleen after human allogeneic bone marrow transplantation

The cellular composition of the spleen has been assessed in 18 patients who died 15-326 days after receiving allogeneic marrow for leukaemia. The white pulp showed marked lymphocyte depletion with no germinal centres, very few B cells, and rare plasma cells. The marginal zone was unrecognizable but there were moderate numbers of T cells in the periarteriolar lymphatic sheaths (PALS), showing great variation in CD4/CD8 ratio. The percentage of CD4+ cells decreased with time post transplant. CD8+ cells were reduced in patients with graft-versus-host disease (GvHD) who also showed no increase in cells staining for activation markers. No T cells were detected expressing immature phenotypes and no differences were detected between patients who received marrow purged or unpurged of T cells. Macrophage numbers appeared normal. Extramedullary haemopoiesis (EMH) was predominantly in the red pulp greater than 30 days after transplantation but more commonly in the white pulp before then. Pyknotic cells were common in seven cases and appeared to be associated with EMH rather than GvHD. Chimaeric studies demonstrated small numbers of donor cells in the PALS at 26 days and larger numbers at 56 days.     

Chicken B-cell-activating factor: regulator of B-cell survival in the bursa of fabricius

Previous studies on mammals have demonstrated that a tumour necrosis factor family member, B-cell-activating factor (BAFF) (BlyS, TALL-1), is mainly produced by myeloid and dendritic cells and that BAFF promotes B-cell differentiation and survival in a paracrine fashion. We have recently shown that BAFF is upregulated at the bursal stage of the avian B-cell development. We now show that the avian bursal B cells and B-cell lines, RP-9, RP-13 and DT40, express chicken BAFF (cBAFF). In situ hybridization confirms strong cBAFF expression within the bursal follicles. Like mammals, cBAFF is expressed in the avian myeloblast and myelomonocytic cell lines but not in the peripheral blood alphabeta and gammadelta T cells. The binding of recombinant human BAFF (hBAFF) to the bursal B-cells indicates a conserved receptor-ligand binding. Furthermore, the recombinant hBAFF has a positive effect on bursal cell proliferation and transiently inhibits cell death in vitro. In conclusion, cBAFF is highly conserved structurally, but as a novel observation we suggest cBAFF to function in an autocrine fashion to promote the growth and maturation of follicular B cells in bursa of Fabricius.     

Investigation of the cellular composition of the bone marrow in monkeys after repeated puncture

Summary The changes in the cellular composition of the bone marrow were studied in 5 monkeys of the speciesPapio hamadryas. The bone marrow was obtained from the tibial tuberosity of both extremities with the aid of I. A. Kassirskii's needle. Experiments were conducted for a period of 6–9 months in the morning hours, before feeding the animals, once a week. The absolute number of leukocytes in the punctate decreased as a result of frequent punctures; the normal cell ratio in myelograms was disturbed. Qualitative changes also occurred in the peripheral blood. The changes observed were very stable and persisted for a long time.(Presented by Active Member AMN SSSR V. V. Parin) Translated from Byulleten Éksperimental noi Biologii i Meditsiny, Vol. 50, No. 8, pp. 112–115, August, 1960     

The influence of age on Campylobacter jejuni infection in chicken

Campylobacter jejuni (C. jejuni)-host-interaction may be affected by the maturation stage of the chicken's immune system and the developing gut microbiota composition. We compared these parameters between birds C. jejuni-inoculated at day one, 10, 22 and 31 post hatch. The highest C. jejuni-colonization rate and numbers of colony forming units (CFU) were detected in caecal content of day-one-inoculated birds while the lowest was detected in 22-days-old birds. The low bacterial colonization of 22-days-old chickens correlated with the most prominent immune reactions in this age group in comparison to other age groups. Age and C. jejuni-inoculation had a significant effect on lymphocyte numbers and cytokine expression levels in caecum as well as on gut flora composition. Overall, the immune response to C. jejuni is significantly influenced by the age of the infected chickens leading to differences in C. jejuni-colonization pattern between age goups.     

The cellular composition of human lymph nodes after allogenic bone marrow transplantation: an immunohistological study

Using immunohistological techniques, the cellular composition of lymph nodes was assessed in 18 patients who had died 15 to 326 days after allogeneic bone marrow transplantation for leukaemia. The lymph nodes showed reduced cellularity of the cortex and paracortex, dilated sinuses and no lymphoid follicles. The majority of leucocytes were T lymphocytes with an inversion of the normal T4:T8 ratio. No cells were detected expressing immature cortical thymocyte antigens, using NA1/34 and OKT10, but an excess of T11 (E rosette receptor)+ cells over the sum of T4+, T8+ and HNK1+ cells raised the possibility of the presence of immature cells. B lymphocytes were extremely rare and present as clusters in only two patients. Despite this, plasma cells were prominent in many cases and their number increased with time post transplant. The predominant immunoglobulin heavy chain class was IgA in seven cases, IgG in three cases, IgM in two cases and IgE in one case with no relationship between dominant class and days post transplant. In patients with graft-versus-host disease (GvHD), there was a significantly lower T4:T8 ratio but no increase in expression of lymphocyte activation markers. Pyknotic leucocytes were present in half of the cases with GvHD and none of the other cases. No differences were detected in patients who had received marrow purged with monoclonal antibodies (Campath-I or UCHT1). Chimeric studies on three recipients of one haplotype matched marrow, using a monoclonal antibody specific for HLA-A2 and A28 antigens, showed a significant influx of donor cells by 56 days but this did not appear to be an immediate prelude to full morphological reconstitution.     

Detection of bursa and thymus-specific alloantigens in the chicken.

CH strain chickens selected from the F2 progeny of a cross between CH (B10/10) and B14B (B14/14) strains carried bursa (BA) and thymus (TA)-specific alloantigens of B14B parental origin. The BA marker was present on 95% of bursal cells but only on 10% of splenic and blood B lymphocytes. The TA marker was expressed by 80% of thymus cells and weakly by 45% of splenic and 70% of blood T lymphocytes. The adopted immunological and genetic protocol offers a feasible approach towards detection of differentiation antigens in major histocompatibility complex-homozygous but 'minor' alloantigen-segregating populations.     

Dome epithelium and follicle-associated basal lamina pores in the avian bursa of fabricius

Background: The immunological role played by the avian bursa of Fabricius has been well established. Although numerous studies have also reported on the development and general morphology of this organ, some structure-function relationships still hae not been fully explained. Methods. Bursae from chickens at three developmental stages were removed and examined by scanning electron micropscopy. Routine preparation was used as well as sonication (Microdissection). Micrographs were used for qualitative morphological study and for quantitative morphometric analyses. Results: Routine SEM observations were similar to those previously reported in the literature. Sonicated specimens allowed topographical study of various levels of surface erosion. Two types of surface cells were observed: typical absorptive epithelium and follicle-associated epithelial (FAE) cells. Erosion of the dome surface epithelium revealed basal lamina pores n the region over the subepithelial lymphoid follicles. These pores were present at hatching. Morphometric analysis of dome and pore areas. Conclusions: Basal lamina pores may provide a communication route between the lympghoid follicles and the external environment via the FAE cells. Also, the close association between the FAE cells of the epithelial domes, the epithelial pores, the capillary complex of the previously described bursal-blood barrier, and the subepithelial lymphoid follicles could represent a morphological “pure complex” that matures early in posthatching development and may be related to the immunological function of the bursa. © 1995 Wiley-Liss, Inc.     

The influence of age on adaptive bone formation and bone resorption

Bone is a tissue with enormous adaptive capacity, balancing resorption and formation processes. It is known that mechanical loading shifts this balance towards an increased formation, leading to enhanced bone mass and mechanical performance. What is not known is how this adaptive response to mechanical loading changes with age. Using dynamic micro-tomography, we show that structural adaptive changes of trabecular bone within the tibia of living mice subjected to two weeks of in vivo cyclic loading are altered by aging. Comparisons of 10, 26 and 78 weeks old animals reveal that the adaptive capacity diminishes. Strikingly, adaptation was asymmetric in that loading increases formation more than it reduces resorption. This asymmetry further shifts the (re)modeling balance towards a net bone loss with age. Loading results in a major increase in the surface area of mineralizing bone. Interestingly, the resorption thickness is independent of loading in trabecular bone in all age groups. This data suggests that during youth, mechanical stimulation induces the recruitment of bone modeling cells whereas in old age, only bone forming cells are affected. These findings provide mechanistic insights into the processes that guide skeletal aging in mice as well as in other mammals.