Chicken thymocyte-specific antigen identified by monoclonal antibodies: ontogeny, tissue distribution and biochemical characterization

Identification of a T3/T cell receptor complex in chickens

A mouse mAb, CT-3, recognizes on chicken T cells a complex of three polypeptides, Mr 20,000, 19,000, and 17,000, two of which are N-glycosylated. The CT-3 antibody is mitogenic for chicken T cells, and it coprecipitates two additional polypeptides of Mr 49,000 and 38,000 in lysates of T cell membranes. Ontogeny studies revealed that 5-6 d after thymic influx of hemopoietic stem cells, their thymocyte progeny begin to express the T3/TCR complex. After hatching 1 wk later, the CT-3+ cells begin splenic migration in large numbers.

A novel cell surface molecule on early B-lineage cells

B cells and their antibody-secreting progeny represent one of several differentiation pathways that haematopoietic stem cells (HSC) may enter. Cells representing intermediate stages between HSC and B cells have been identified in mammalian haematopoietic tissues and studied intensively over the past decade. This population of early B-lineage cells, termed pre-B, is characterized by cellular proliferation and an orderly cascade of immunoglobulin gene rearrangements, a combination of events leading to the generation of clonally diverse B cells which then migrate to peripheral lymphoid tissues. It remains to be determined what elements determine the polyclonal growth of pre-B cells, how immunoglobulin gene rearrangements are regulated, and what happens to pre-B cells undergoing 'non-productive' immunoglobulin gene rearrangements. These issues could be resolved more easily if early B-lineage cells could be identified precisely and isolated. Here, we describe a cell surface glycoprotein that is selectively expressed by pre-B and newly formed B cells in murine haematopoietic tissues. The molecule, a homodimer formed by disulphide-linked chains of relative molecular mass (Mr) 140,000, is identified by a mouse monoclonal alloantibody called BP-1.

Effect of testosterone treatments for varying periods on autoimmune development and on specific infiltrating leukocyte populations in the thyroid gland of obese strain chickens

Spontaneous autoimmune thyroiditis (SAT) is detectable by 2 weeks of age in the obese (OS) strain of chicken, and by 6 weeks virtually all of these animals have severe lymphoid infiltration of the thyroid. During the interval from hatching to 6 weeks of age, testosterone implants were administered for varying periods. All treatment groups were terminated at 6 weeks. Testosterone administered shortly after hatching increased thymus weight, depressed bursa weight, and reduced the severity of SAT, as measured by lymphoid infiltration of the thyroid and circulating thyroglobulin autoantibody concentrations. Birds supplemented with testosterone at later intervals exhibited depressed bursa and thymus weight; however, the severity of SAT was not affected. In a second experiment, the treated group was administered testosterone for the first 2 weeks after hatching. Thyroids were histologically examined at 2 and 6 weeks using a panel of five monoclonal antibodies (anti-Ia, anti-IgM, anti-IgG, anti-T cell, and antithymocyte). Compared with untreated controls, testosterone treatment reduced the frequency of Ia+ cells, T cells, and IgG+ cells in the thyroid. This treatment did not affect the frequency of IgM+ cells, and perhaps slightly increased the frequency of thymocytes. These results suggest that testosterone's suppressive effects are associated with changes in thymic development and effector T-cell and regulator T-cell activity.

Monoclonal antibodies directed towards the two major cell populations in the bursa of Fabricius of the chicken

Two mouse monoclonal IgM antibodies, B.1 and B.2, have been produced using the mouse myeloma cell line Sp2/0-Ag 14 and spleen cells from mice immunized with chicken bursa cells. The binding of the monoclonal antibodies to cells in suspension or tissue sections was demonstrated by means of the unlabeled peroxidase-antiperoxidase method. B.1 recognizes 61% of the bursa cells, 10-14% of the cells of spleen and of the peripheral mononuclear blood leukocytes and 1% of the thymus cells. The B.1+ cells are regarded as B cells. Their location in tissue sections corresponds with the known B-dependent areas of lymphoid organs. Competitive binding and double marker experiments proved that the B.1 antigen is distinct from surface immunoglobulin (Ig). In the bursa all B.1+ cells are also Ig+, whereas in the thymus, spleen and blood only about 90% of the B.1+ cells show this conformity. B.2 mainly recognizes so called reticular epithelial and reticular cells of the bursa (36%), thymus (20%) and spleen (13%). The B.2+ cells represent the second major cell population of the bursa.

Chicken thymocyte-specific antigens identified by monoclonal antibodies: characterization and distribution in normal tissues and in tumoral tissues from Marek's disease chicken

Monoclonal antibodies (MAbs) were obtained against purified thymocyte membrane extracts. Five MAbs TA3, TB1, TB6 (IgG1), TC4, and TA1 (IgG2a), were tested by immunofluorescence and by immunoperoxidase tests against normal cells from different organs, Marek's disease (MD) cell lines, and MD tumoral cells from chickens. Three of them, TA3, TB1, and TB6, reacted exclusively with lymphoid cells in both cortical and medullary areas of the thymus and with less than 8% bursa cells. They identified a protein of apparently 40 kD. The other two revealed antigenic determinants on most medullar thymocytes and some cortical thymocytes, and on some splenic and peripheral blood lymphocytes. They were positive with MD cell lines and cells deriving from MD tumors. TC4 and TA1 detected molecular masses of about 110 kD and 16 kD, respectively. No MAbs reacted with erythrocytes, bone marrow, liver, brain, and skin cells. Not all of the tested cells were stained after contact with an anti-chicken immunoglobulin serum. In this paper, we determine a specific antigen restricted to T cells from thymus and different markers belonging to the mature T cells. The latter are also present on MD cell lines and MD tumoral cells.

Novel heterophile chicken antigen: immunohistochemical localization using antisera to Mycobacterium smegmatis and possible association with lymphocyte maturation

A novel heterophile antigen shared by Mycobacterium smegmatis and chicken tissues was demonstrated by the indirect immunoperoxidase method using antisera raised in rabbits immunized with a complete Freund's adjuvant containing killed Mycobacterium smegmatis as an immunostimulating component. This antigen was strongly expressed in medullary lymphocytes of the thymus and bursa of Fabricius, but was undetectable in lymphoid cells of the cortical regions of these organs. Only a few lymphocytes stained positively for the antigen in T- and B-cell areas of the spleen. These data suggest that the heterophile antigen is associated with the intrathymic and intrabursal maturation of chicken lymphocytes. The antigen was also detected in some nonlymphoid cells. It was not found in sheep erythrocytes, human and rat tissues or in killed bacillus Calmette--Guerin.

Levels of c-myc oncogene mRNA are invariant throughout the cell cycle

The steady-state messenger RNA levels of several genes increase when cells are stimulated to proliferate. The transcripts from one such gene, the proto-oncogene c-myc, increase approximately 20-fold shortly after cells are stimulated to proliferate and then decline before the onset of DNA synthesis. It has been inferred from these data that expression of c-myc may be specific to the G1 portion of the cell cycle. Alternatively, this transient increase in c-myc mRNA following the stimulation of quiescent cells could be the result of an activational event that renders the cells competent to enter the cell cycle. To distinguish between these possibilities, we performed experiments to determine whether the amount of c-myc mRNA fluctuates during the cell cycle in cells that are under constant stimulation to proliferate. Although c-myc mRNA does undergo a transient increase within 2 h of serum stimulation of quiescent serum-deprived cells, our results show that the level of c-myc mRNA is constant throughout the cell cycle and does not diminish in density-arrested cells maintained in the presence of serum growth factors. In contrast to c-myc, the mRNA levels of two other genes whose expression has been associated with cellular proliferation do show consistent variations within the cell cycle. Both thymidine kinase (TK) and histone 2b (H2b) mRNA levels increase during S phase in continuously growing cells and decrease when cell replication ceases in density-arrested cultures. Therefore, the transient increase in c-myc transcription following the activation of quiescent cells is not due to the type of cell cycle-dependent regulation characteristic of the TK and H2b genes.

Tissue distribution and ontogenic appearance of a chicken T lymphocyte differentiation marker

A monoclonal antibody, designated T10A6, was produced by immunizing mice with H.B14 chicken thymocytes. T10A6, when tested by immunofluorescence, labeled 80% of thymocytes, and a subset of peripheral T cells: 20% of spleen leukocytes, 10% of blood leukocytes, 8% of bone marrow cells but less than 1% of bursal lymphocytes. Tissue distribution on polyethylene glycol sections showed that in the thymus T10A6 stained most cortical thymocytes and a portion of medullary cells. In the spleen, the positive cells appeared scattered mainly in the T-dependent areas. Ontogenic studies revealed that the antigen recognized was found in the chick embryo thymus from day 11 onward and the expression of this antigen on thymocytes reached the adult level from day 13. The first positive cells were detected in the spleen on day 13 of embryonic life. T10A6 (IgG1) precipitated a 65-kDa material from thymocytes. This is the first description of a monoclonal antibody recognizing a peripheral T cell subpopulation in chicken.

DNA ligases as markers of lymphoid cell maturation and heterogeneity in the chicken

The activities of 8 S and 6 S DNA ligases have been studied in the chicken lymphoid cells of blood, spleen and bursa of Fabricius at different stages of development, from late embryonic life to about 3 months after hatching. These cells have been sorted with the fluorescence-activated cell sorter FACS II on the basis of size and T or B antigenicity (immunofluorescence). The light 6 S DNA ligase has been previously demonstrated to be associated to a late stage of differentiation of thymocytes. In the bursa, a unique form of 8 S DNA ligase is found during the whole period of observation. This form of enzyme remains in the B cells of the spleen until 3 weeks after hatching, but is never present in the blood B cells. As far as T cells are concerned, the light DNA ligase is present in the blood from 18-day embryonic life on. In the spleen T cells, on the contrary, this enzyme appears only 3 weeks after hatching. Before this stage, splenic T cells are devoid of any form of DNA ligase activity. These findings show biochemical differences in T and B lymphocytes colonizing the periphery, blood and spleen, and suggest, at least for the T cells at early stages, a heterogeneity in the degree of differentiation.