Bursa lymphocytes and IgM-containing cells in chicken embryos bursectomized at 52-64 hours of incubation

Immunohistochemical evidence that gonads and gonad-associated tissues are sites for enrichment with immunoglobulin-containing cells in adult chickens

Immunohistochemical staining of tissue sections prepared from gonads and gonad-associated tissues obtained from adult chickens was performed in order to assess the possibility that these tissues may be sites of enrichment with IgM-containing cells in various B lineages. Evidence is presented which suggests that IgM-containing B lineage cells are present in 1) the ovarian stroma and subcapsular areas of the ovary and 2) the interstitium and subcapsular areas of the epididymis of the testes. These represent new sites reported for B lineage cells in adult chickens. Some questions relevant to the physiologic, ontogenetic, and phylogenetic implications of these observations relative to vertebrate hematolymphopoietic processes are included.

The bursa of Fabricius: the evolution of a discovery

It has been a joy these past 40 yr to have traveled the "Bursal Road"--a road we helped construct and whose route allowed us to make a variety of observations that contributed either to basic science or indirectly or directly to the role of the bursa of Fabricius in the B cell repertoire. The chicken's bursa of Fabricius introduced me to endocrine, heritability, and growth studies, which allowed serendipity to occur and the revelation of the classical and modification of the classical theses of bursal function. The modification of the classical thesis, presence of immunoglobulin in the absence of the bursa, raised questions that directed us to study hypothalamic control of behavior, which was not directly related to bursal function. This forced us to learn various techniques, e.g., autoradiography, cell labeling, and electron microscopy, that made it possible to study long- and short-lived lymphocytes, lymphokines, labeled cells, and the fine structure and function of the bursa of Fabricius, cecal tonsil, Harderian gland, lymph nodes, Meckel's diverticulum, Pineal gland, and spleen. In an attempt to use cyclophosphamide to understand how the spleen acquired the ability to produce antibodies, we revealed a dendritic cell in the bursa, the bursal-secretory dendritic cell (BSDC), and in the spleen, the ellipsoid-associated cell (EAC). The BSDC is a novel cell in the bursal microenvironment and may be involved in an interaction with prebursal or bursal stem cells, leading to the differentiation or selection of the B cell repertoire of the chicken.

Immunoglobulin-containing cells in chick embryo urogenital tissues: a new site for early B lineage cells in endothermic vertebrates

We have employed histological and immunofluorescent staining procedures in order to characterize the distribution of mu + B lineage cells in tissue sections prepared from developing chicken embryo urogenital tissues (UGTs) between 14 and 21 days of incubation. B lineage cells were observed in tissue sections prepared from developing UGTs, especially the mesonephros and its associated tissue, throughout the sample period. The highest densities of mu + B lineage cells were observed in tissue sections prepared from 18 day embryos. The mu + UGT cells were distributed singly and in clusters in subcapsular regions and within the peritubular interstitium of the mesonephros. These observations (1) are consistent with those which suggest nonbursal site(s) for origin of cells in B lineage, (2) may help account for the varying effects of embryonic caudectomy performed between the second and third days of incubation and surgical bursectomy performed close to hatching, (3) may help provide new insights on the effects of sex hormones on B cell development, and (4) suggest fundamental ontogenetic and phylogenetic similarities between developing vertebrate immune systems.

Effect of surgical and chemical in ovo bursectomy on lymphocyte density scores and histological evaluations of primary and secondary lymphoid organs in hypertensive and hypotensive turkeys

The effects of surgical and chemical in ovo bursectomy on the histology of primary and secondary lymphoid organs were studied in hypertensive and hypotensive lines of turkeys. The effects of bursectomy were measured by determining the presence of lymphatic nodules and the presence of lymphocytes in secondary lymphoid organs: spleen, cecal tonsil, Meckel's diverticulum, and Peyer's patches; as well as in the thymus and bursa of Fabricius. No treatment effect on splenic nodule formation occurred, but a significantly lower lymphocyte density score was present in the surgically bursectomized group. Both nodule formation and lymphocyte density scores for the cecal tonsil and Peyer's patches were significantly reduced in the surgically bursectomized and testosterone-treated groups as compared with the control and sham groups. The most consistent depression in lymphatic scores in both the surgically and chemically bursectomized groups occurred in the Peyer's patches followed by cecal tonsils and Meckel's diverticulum. As expected, there were no differences in thymocyte density scores. There was no consistent effect on lymphatic scores due to blood pressure selection; however, the hypertensive line showed significantly lower scores than the hypotensive line in the bursa, cecal tonsils, and Peyer's patches. No differences between the sexes were noted in any organ.

Suppression of chicken J chain production by in ovo bursectomy

The influence of in ovo bursectomy on the levels of J and mu chains in the sera of embryonic and hatched chicks was studied by the dot blotting immunoassay. The results indicated a decrease in the level of J chains during the embryonic stage after treatment with testosterone compared with normal chicks. Testosterone treatment caused a decrease in J-chain levels after hatching which was more marked in reduced-alkylated than in non-reduced sera. In contrast, testosterone caused no significant change in serum levels of mu chains, either in ovo or after hatching. Our findings further present the paradox that although removal of the bursa of Fabricius by testosterone treatment did not impair mu-chain synthesis, B-cell differentiation was suppressed. These observations indicate that in ovo bursectomy selectively inactivates B-cell differentiation as indicated by the induction of immunodeficiency, and results in the failure of J-chain production.

Neuroimmune interactions: experimental and clinical strategies

This historical mini-review is devoted to the 30th Anniversary of the research activities of the Neuroimmunomodulation Group at the Immunology Research Center of Belgrade. During the past 30 years, these scientists have contributed to: (a) the definition of the structural and functional complexity and the lymphoneuroendocrine web of the immune microenvironment; (b) the structural and functional dissection of the neuron, brain and mind by means of anti-neural antibodies; (c) the antigenic relationship among the multiple components of the nervous and lymphoid tissues; (d) the methodological and conceptual aspects of the influence of lesioning and stimulation of various brain structures on immune responsiveness; (e) the lymphoneuroendocrine relationships during embryonic development; (f) the definition of immunopsychiatric diseases, i.e., neural tissue immunologic hypersensitivity in psychiatric diseases; (g) the immunomodulating and regulating activity of methionine-enkephalin and leucine-enkephalin; (h) the correlations between associative learning and immunity (behavioral immunology). The theoretical, experimental and clinical devices created, and observations collected from 1957 to 1987 by the Belgrade group of neuroimmunologists proved to be useful for elucidation of the complex interactions between the immune system and the nervous system, and provided a broad perspective for research in neuroimmunomodulation.

Review of studies on the immunological capacity in the bursectomized chick

This paper summarizes data on the immunological capacity in the bursectomized chick. A series of experiments described by Glick and Sadler represented the functional importance of the bursa of Fabricius for the humoral immunity in chicken. Later studies of immune responses in bursaless chickens reported by Lerner et al. contributed to our knowledge of bursa-independent humoral immunity and demonstrated an extra-bursal site for B-cell differentiation. Bursectomy at an early stage of chicken development changes the immune responses after hatching. Here I present my current understanding of embryonic B-cell populations (bursa-dependent and independent) following in ovo bursectomy which may influence B-cell differentiation with reference to our experiments on J chain production.

Oncogene expression in reticuloendotheliosis virus-transformed lymphoid cell lines and avian tissues

The genome of reticuloendotheliosis virus (REV-T) contains a unique oncogene, designated v-rel, which is inserted into the env region. Employing a cloned rel DNA probe, a single 2.9- to 3.0-kilobase v-rel mRNA was identified in poly(A)+ RNA from REV-T-transformed lymphoid cell lines. A 4.0-kilobase rel-specific transcript corresponding to the cellular homolog of the v-rel oncogene was identified in MSB-1 cells, a herpesvirus-transformed lymphoid cell line. Cytodot hybridization was used to quantitate the levels of rel, c-rel, c-myc, c-myb, c-abl, c-fms, c-Ha-ras, c-Ki-ras, c-src, c-yes, c-mos, and c-sis mRNA in REV-T-transformed cells. The levels of rel transcription in REV-T-transformed cells were elevated only two to eightfold over levels found in the transformed immature avian lymphoid cell line MSB-1. The relatively modest levels of rel transcription in REV-T-transformed cells and the significant differences between the lengths of the v-rel and c-rel mRNA suggest that REV-T transformation is the result of the production of an altered rel protein. The c-rel proto-oncogene is expressed in all avian hematopoietic tissues but is not expressed at significant levels in brain and muscle. The transcription of other proto-oncogenes is not enhanced in REV-T-transformed lymphoid cell lines.

Defect in the generation of light-chain diversity in bursectomized chickens

The avian bursa of Fabricius has been regarded as a central organ for B-cell development, but there is controversy about the existence of other sites for differentiation of B cells. We have recently shown that chickens surgically bursectomized as early embryos, before the bursal primordium appears, can produce cytoplasmic, surface and serum immunoglobulins of IgM, IgG and IgA classes but are unable to generate specific antibodies in response to antigen. We have therefore examined the structure and diversity of immunoglobulins of bursectomized chickens. Analysis of serum IgG revealed normal gamma-heavy chains but altered light chains with more basic and less diverse isoelectric points than normal. These light chains may represent germ-line specificities not diversified by somatic mutations. Thus the bursa of Fabricius appears not to be necessary for the production of immunoglobulin molecules as such but to function in the creation and expansion of the antibody repertoire, possibly by providing a microenvironment for somatic mutations.

Ontogeny of primary lymphoid organs and lymphoid stem cells

Cells of the immune system go through a series of important developmental steps that begin early in embryonic life and include, first, the various waves of hemopoietic-cell production in the embryo and, second, the homing of these cells to the hemopoietic organs, which are the sites of hemopoiesis and lymphopoiesis in embryonic and adult life. The avian embryo is an important model for investigating these early steps; and this paper presents a comprehensive review of the work done on the early ontogeny of the avian immune system.

Immune capacity of the chicken bursectomized at 60 hr of incubation: cytoplasmic immunoglobulins and histological findings

Chickens were surgically bursectomized at 60 hr of incubation, before the bursal anlage appears. Completeness of the bursectomy was confirmed at autopsy at 10 weeks of age. These embryonically bursectomized (Bx)3 chickens are known to produce immunoglobulins of IgM, IgG, and IgA classes but so far no specific antibodies have been observed even after heavy immunization. The Bx chickens had mature plasma cells in an almost normal frequency when studied at 10 weeks of age. The amount of germinal center formation in the spleen and cecal tonsils was markedly decreased when compared to the control (Co) chickens. Also, the frequency of cytoplasmic IgA-positive (c-IgA+) cells was severely decreased in the Bx animals, whereas the occurrence of c-IgG+ and c-IgM+ cells was not affected to the same extent. These findings support the hypothesis that heavy-chain class switch may occur without the bursal influence, and that the bursa of Fabricius is essential only for expansion or creation of the antibody repertoire.

J chain-positive cells in bursectomized chicks

Using embryonic chickens treated with testosterone propionate, the effects of congenital absence of the bursa of Fabricius determined by the frequency of J chain-positive cells was examined in the spleen, thymus and bone marrow at the embryonic and newly hatched stages. J chain-positive cells in the chicks without bursa were reduced in the spleen. No differences in the numbers of the cells were detected in the thymus and bone marrow. These results imply that removal of the bursa of Fabricius cannot entirely prevent the generation of J chain-positive B cells. Furthermore, these results partly suggest the important role of the bone marrow in the proliferation of some J chain-positive cells in chicks without bursa.

Immunological responsiveness of the pigeon (Columba livia) following neonatal bursectomy

Pigeon squabs in two separate experiments were surgically bursectomized ( BSX ), surgically sham bursectomized ( SBSX ), or maintained as non-surgical controls (CON). Surgical procedures were performed within 2 hr of hatching. Primary and secondary hemagglutinin (HA) responses, as well as mercaptoethanol sensitive (ME-S) and resistant (ME-R) levels, to sheep red blood cells (SRBC) were quantitated. BSX did not reduce HA responses, nor ME-S and ME-R levels.

Immune capacity of the chicken bursectomized at 60 hours of incubation: failure to produce immune, natural, and autoantibodies in spite of immunoglobulin production

Chickens surgically bursectomized at 60 hr of incubation were immunized at the ages of 6, 7, 8, and 9 weeks with Escherichia coli lipopolysaccharide, levan, tetanus toxoid, and dinitrophenyl-bovine serum albumin. All antigens were given on each occasion. All embryonically bursectomized (BX) chickens had detectable concentrations of serum IgM, IgG, and IgA. On the whole, the IgG level was markedly decreased and the levels of IgM and IgA were normal. Concentrations of serum immunoglobulins did not change during immunization in the BX chickens. In spite of the production of serum immunoglobulins the BX chickens were unable to respond to the immunization by production of specific antibodies, whereas the control (CO) chickens produced good antibody response to each antigen used. The BX chickens also lacked both natural antibodies to phosphorylcholine, fecal bacteria, rabbit red blood cells (RRBC), and MHC antigens and autoantibodies to the liver, kidney, and thyroidea. Neither were any antibodies to the bursal structures observed. These results support the hypothesis that the bursal influence is not necessary for isotype switch, but is essential for the production of specific antibodies.

Immune capacity of the chicken bursectomized at 60 hours of incubation: transplantation of bone marrow cells of the bursectomized chickens into cyclophosphamide-treated newly hatched recipients

Chickens bursectomized at 60 h of incubation are known to be able to produce immunoglobulins (Ig) but not specific antibodies. In the present work bone marrow (BM) cells of 2- and 10-week-old embryonically bursectomized (Bx) chickens were transferred to newly hatched cyclophosphamide-treated chickens for the purpose of studying whether the transplanted cells home into the bursa and gain a capacity to produce specific antibodies. BM cells of normal 2- and 10-week-old chickens were transferred as controls. Cells of 2-week-old control (Co) and of 2- and 10-week-old Bx chickens could to some extent reconstitute serum Ig of the recipients, but were totally incapable of homing into the bursa and of restoring the specific antibody production. Only BM cells of 10-week-old Co chickens could restore the production of specific antibodies without homing into the bursa, indicating their postbursal nature. These findings indicate (a) that 2- and 10-week Bx BM cells have irreversibly bypassed the bursal phase of education, (b) that also the normal BM at the age of 2 weeks contains cells that are capable of Ig but not of specific antibody synthesis and (c) that bursal microenvironment is not necessary for isotype switch, but is essential for creation and expansion of the antibody repertoire.

The percentage of T- and B-cells in the lymphomyeloid tissue of hyperimmunized bursaless chickens

Bursa or bursa follicles failed to develop when 3-day-old embryonated eggs were dipped in 2% testosterone propionate in ethanol. The chicks from the treated and control eggs (TP-chicks) were hyperimmunized with sheep red blood cells and the percentages of thymus-derived (T) and bursal-derived (B) lymphocytes in different lymphoid organs determined. The percentage of T-cells in the thymus of TP-embryos was not significantly affected, but the B-cell population was significantly depressed. The percentage of B-cells in peripheral blood, spleen, and bone marrow of TP-hyperimmunized chickens was significantly below that of controls. These data support previous observations of B-cells in bursaless birds. The significantly higher percentage of T-cells in the bone marrow of TP-birds is discussed in relation to T-suppressor cells.

Ontogeny and distribution of cells in B lineage in the American leopard frog, Rana pipiens

Two-color immunofluorescence techniques were used in order to trace the development and distribution of cells expressing immunoglobulin in Rana pipiens. Evidence is provided which suggests that (i) embryo-larval urogenital tissues are sites of generation of cells in B lineage, (ii) during ontogeny, there is a sequential expression of immunoglobulin isotypes on B cell surfaces, (iii) larvae are able to produce the full range of immunoglobulin clases found in adults, and (iv) at least two subpopulations of lymphocytes exist in Rana pipiens, sIg+ and sIg-; thymocytes and presumably peripheral T cells lack conventional surface immunoglobulin. Some ontogenetic and phylogenetic implications are discussed.

Avian reticuloendotheliosis virus: identification of the hematopoietic target cell for transformation

Non-virus-producing hematopoietic cells transformed in vitro by reticuloendotheliosis virus (REV-T) induce lethal "reticuloendotheliosis" when inoculated into histocompatible chickens. This is the first direct demonstration that an in vivo target cell of an avian acute leukemia virus can be transformed in vitro. The tumorigenic, REV-T-transformed non-virus-producing cells fail to express helper-virus-coded proteins. REV-T transformed tumorigenic cells therefore do not require helper-virus functions. Cells transformed in vivo or in vitro by REV-T have lymphoblastoid morphology and express low levels of terminal-deoxynucleotidyl-transferase activity and bursal-cell determinants. One clone synthesized Ig mu. The preferred target cells for REV-T transformation are therefore immature lymphoid cells that express B-cell determinants. We propose that the unique transforming sequence of REV-T be designated rel (lymphoid).

Alkaline phosphatase in the developing bursa of Fabricius. A comparative study of the cyclophosphamide- and testosterone-induced immunodeficiencies in the chick embryo

The ontogeny of alkaline phosphatase in the bursa of Fabricius was studied by histochemical and biochemical methods. According to the quantitative determinations, the activity of alkaline phosphatase increased from the 11th to 17th day of incubation--that is, during the time of the lymphoid follicle formation in the developing bursa. The activity was localized in the mesenchymal tissue surrounding the lymphoid follicles. Testosterone given in ovo prevented the appearance of alkaline phosphatase in the bursal mesenchyme but had no effect on the activity of the embryonic liver. In contrast, in ovo treatment with cyclophosphamide had no effect on the alkaline phosphatase in the bursa. By using transplantation of embryonic bursal stem cells, it was further shown that, in contrast to cyclophosphamide, testosterone destroys the capacity of the bursa to serve as a differentiation site for the B-cell lineage. The results indicate that testosterone affects the stromal cells of the bursa, whereas cyclophosphamide destroys only the lymphoid population undergoing differentiation and leaves the bursal stroma intact.