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In-vitro evidence suggests that DNA methylation may be involved in the development of forbidden immune responses that can result in autoimmune disease. In the present study we examined in-vivo effects of 5-azacytidine (5-azaC), a substance that inhibits DNA methylation, on the immune system and the occurrence of a spontaneous autoimmune disease in the chicken model. We found that (1) treatment of young normal chickens with 1.0 mg/kg 5-azaC on 7 consecutive days caused a rapid degeneration of the central lymphoid organs thymus and bursa; (2) this regimen with 5-azaC apparently inhibited B cell maturation, as the frequency of cytoplasmic Ig+ plasma cells in the bone marrow was found to be significantly reduced, whereas the total number of bone marrow cells was unchanged; and (3) a chronic low-dose (0.5 and 1.0 mg/kg) application of 5-azaC through 6 weeks was found to significantly enhance the spontaneous autoimmune thyroiditis in newly hatched chickens of the Cornell C strain, as determined by anti-thyroglobulin autoantibody titres and histological analysis of thyroid gland infiltration. The possible implications of these data for the generation of pathogenic autoimmune responses are discussed.

High concentrations of unsaturated fatty acids are known to cause hemolysis. At low concentrations, however, unsaturated cis fatty acids have been found to protect erythrocytes against hypotonic hemolysis. In the present experiments we examined the effect of oleic (18:1), linoleic (18:2), linolenic (18:3), and elaidic (18:1) acid on the osmotic fragility of chicken and sheep erythrocytes, which markedly differ in their resistance to osmotic rupture. The results are summarized as follows: (A) The phenomenon of stabilization was observed in both species alike. (B) Interaction of cells with the fatty acids under isotonic conditions led to a persistent stabilization, i.e., the cells remained more resistant against osmolysis even after several washings. (C) Oleic and elaidic acid protected against osmotic rupture with a high degree of specificity. Linoleic and linolenic acid were much less protective. Thus, this effect appears to be specific for one double bond. (D) Contrary to the unsaturated fatty acids with cis configuration, elaidic acid with the trans configuration showed no biphasic behaviour, and even at the highest concentrations applied no hemolysis was observed.

In contrast to systemic autoimmunity, spontaneous autoimmune thyroiditis of Obese strain (OS) chickens is associated with a marked T cell hyperreactivity in vitro , i.e. an increased proliferation and interleukin 2 (IL 2) secretion in response to Concanavalin A (ConA). In the present study we report an enhanced capacity of OS peripheral lymphoid cells (splenocytes and peripheral blood lymphocytes, PBL) to adsorb fluorescein isothiocyante (FITC) labelled ConA, but not phytohemagglutinin (PHA). However, the elevated ConA binding cannot be a prerequisite for in vitro ConA hyperreactivity as OS thymocytes are normal with respect to ConA binding but nonetheless exhibit elevated responses to this mitogen. Moreover, ConA binding does not correlate with the frequency of cells able to express IL 2 receptors upon short term ConA stimulation. The percentage of ConA activatable cells was found to be increased in OS- PBL as compared to normal control PBL, but was unaltered in OS splenocytes. This finding points to a further mechanism of T cell hyperreactivity in OS chicks in addition to the previously reported defects in nonspecific immunosuppression. Finally, enumeration of cells in the S phase revealed that enhanced proliferation of OS T lymphocytes was not restricted to the in vitro response to ConA and phytohemagglutinin (PHA) but also occurs in vivo .

Monoclonal antibody INN-CH 16 recognizes a surface determinant exclusively present on activated chicken T lymphocytes. The present experiments suggest that this chicken activated T lymphocyte antigen (CATLA) represents the chicken IL-2 receptor or an associated structure, as (i) the kinetics of CATLA expression during T cell activation are analogous to those described for the mammalian receptor for IL-2, (ii) the IL-2 dependent proliferation of mitogen prestimulated chicken lymphocytes is competitively inhibited by INN-CH 16, and (iii) pretreatment of T lymphoblasts with INN-CH 16 drastically reduces their capacity to absorb IL-2 activity from supernatants of mitogen activated chicken lymphocytes.

The Obese strain (OS) of chickens, which is afflicted with Hashimoto-like spontaneous autoimmune thyroiditis (SAT), displays elevated T cell proliferation, interleukin (IL)2 production and IL2 receptor expression upon mitogen stimulation, and defects in the neuroendocrine control of the immune system including elevated corticosteroid-binding globulin (CBG) and a deficient increase of serum corticosterone (CN) upon cytokine injection. Recently this strain has further been shown to harbor retrovirus-related sequences (endogenous virus no. 22, ev22) absent in healthy control strains. To determine the number of genes responsible for SAT-associated immunodysregulation and to unravel possible ev22 associations, we analyzed the above immune and endocrine parameters in F1 hybrids and backcrosses of the autoimmune OS B15B15 with healthy inbred CB B12B12 chickens. OS-like T cell hyperproliferation and IL2 hypersecretion in response to both concanavalin A and phytohemagglutinin were transmitted as autosomal dominant traits and co-segregated in backcross animals. In vivo hyporesponse of the OS to the corticosterone-inducing effect of cytokine preparations was inherited dominantly and the elevated CBG serum levels recessively. None of these traits appeared to be major histocompatibility complex (MHC) linked. However, while T cell abnormalities and elevated CBG serum levels were not associated with the autosomal ev22 locus, in vivo hyporesponsiveness to glucocortocoid-inducing cytokines co-segregated with this OS-specific provirus. These results add to the concept of SAT as a polyetiological and plurigenetic disease and do not support our previous hypothesis that T cell hyperreactivity and immunoendocrine dysfunction might be functionally related.

Stabilization of red cells against hypotonic haemolysis by cis-trans isomeric free C18 fatty acids occurs with pronounced specificity which is strongly temperature-dependent, but in a distinctly different manner for the two configurational isomers. Oleic acid (cis-18:1) stabilizes very efficiently at 0 degrees C, even at the highest concentrations. Elaidic acid (trans-18:1) causes neither stabilization nor haemolysis at this temperature. At room temperature (23 degrees C), elaidic acid acquires the ability to protect, without turning haemolytic at high concentrations. At 37 degrees C elaidic acid also becomes haemolytic. The protecting effect of oleic acid at 0 degrees C is the result of a rapid reaction. The characteristic, temperature-dependent specificity of cis-trans isomeric C18 fatty acid interaction with the red cell membrane appears to be a general phenomenon, since it was observed alike with erythrocytes of different species.

It has been postulated that the establishment of acquired, neonatal immunologic tolerance is due to a "deficit" in interleukin 2 (IL-2). To test this hypothesis, chickens were made immunologically tolerant to both major and minor histocompatibility antigens by transplantation of skin grafts onto newly hatched recipients. In this study, we injected various doses of IL-2 and concanavalin A simultaneously with transplantation and in some cases, several days posttransplantation, and we failed to enhance graft rejection. These results may have practical importance in respect to the clinical use of recombinant IL-2. Injection of IL-2 in and around surviving skin grafts also failed to alter skin graft survival.

The B-L region of the chicken major histocompatibility complex (MHC), the so-called B -locus, corresponds to the murine H-2 I-region. Using alloantibodies and monoclonal antibodies to B-L we analyzed: (a) the tissue distribution of B-L + cells, (b) the function of B-L + cells, and (c) the possible role of B-L + cells in the development of spontaneous autoimmune thyroiditis (SAT) in Obese strain (OS) chickens. The tissue distribution of B-L + cells in peripheral blood and various lymphoid and nonlymphoid organs corresponds to what is known for mammals. In the bursa of Fabricius most lymphoid cells and the dendritic cells carry the B-L antigen; B-L + thymic nurse cells (TNC) first appear on day 17 of embryonic life; chickens possess dendritic B-L + cells in the skin resembling mammlian Langerhans cells; in addition we found that the microglia is unequivocally B-L + . B-L + peripheral blood lymphocytes (PBL) were separated with a fluorescence-activated cell sorter. Ten percent of unstimulated PBL and 60% of phytohemagglutinin (PHA) stimulated T-cell blasts are B-L + . In graft-vs-host (GvH) assays B-L − cells were identified as the effector cells. These cells respond to PHA and concanavalin A (Con A), but not to pokeweed mitogen (PWM). B-L + cells cannot be stimulated by Con A and PHA, but respond to PWM. They possess only a very low activity in GvH assays which can be inhibited by anti-T-cell sera. In OS chickens B-L + /non-B/, non-T and B-L + T (blasts?) cells are found in the “first line” of mononuclear cell infiltration in the thyroid glands. Most interesting, thyroid epithelial cells—which are normally B-L − —become B-L + in the neighbourhood of B-L + infiltrating mononuclear cells. This observation may be of significance for autoantigen presentation and perpetuation in autoimmune thyroiditis. Finally, OS thymuses contain significantly less TNC than normal controls.

Changes in the expression of surface determinants during maturation from central bursa and thymus cells to peripheral B and T lymphocytes in the spleen and peripheral blood in the chicken have been investigated by means of heteroantibodies. The results obtained in membrane immunofluorescence and lymphocytotoxicity assays can be summarized as follows: (1) Turkey antisera specific for bursa (ABS) and thymus (ATS) cells react exclusively with the respective central cell type after exhaustive absorption with peripheral splenic lymphocytes. (2) Antisera raised in rabbits against spleen cells (ASS) and exhaustively absorbed with both bursa and thymus cells recognize surface determinant(s) on a subpopulation of 30 – 40 % of peripheral lymphocytes in spleen and peripheral blood. (3) Double staining and cocapping experiments revealed this peripheral lymphocyte-specific antigen (Lp) on both B and T lymphocytes with no significant steric relationship to B or T lymphocyte markers.

The mitogenic response to Con A and the production of T cell growth factor or interleukin 2 (IL 2) by splenic and peripheral blood lymphocytes of obese strain (OS) chickens with spontaneous autoimmune thyroiditis have been investigated. By using an optimized method with Con A-coated chicken erythrocytes (MRC), lymphocytes of OS chickens were found to exhibit significantly elevated mitogenic responses as compared with cells from either Normal White Leghorn chickens (NWL) or animals of the Cornell C-Strain (CS), from which the OS has originally been developed. This difference was observed throughout ontogeny up to 15 mo of age, and was associated with increased levels of IL 2 activity in the culture supernatants. The elevated responsiveness of OS T lymphocytes was also found to be manifested in the expression of receptors for IL 2, because Con A-stimulated lymphocytes of OS birds were significantly more effective than those from normal controls in absorbing IL 2 activity from conditioned media (CM) of stimulated spleen cells. High concentrations of CM were suppressive in IL 2 assays, signaling the presence of an inhibitory factor(s) in addition to IL 2. An additional indication for defective immunoregulation was that CM from OS lymphocyte cultures showed significantly less of this suppressive activity in comparison with CM of normal (NWL and CS) lymphocyte cultures. Finally, the spontaneous uptake of 125IUdR of embryonic and early post hatching OS spleen lymphocytes was consistently and significantly enhanced. This difference, however, in contrast to the one observed in Con A responses, was found to decrease with age. The data are discussed in view of the contradictory results concerning T cell functions reported for several autoimmune states in mammals.

Lymphocytes were isolated from the infiltrated thyroid glands of 2- to 5-wk-old Obese strain (OS) chickens with spontaneous autoimmune thyroiditis (SAT). Immunofluorescence analysis performed by using a panel of monoclonal and polyclonal antibodies revealed that 60% of thyroid infiltrating leukocytes (TIL) were mature T cells, a large portion of which seemed to be in an activated state bearing Ia-like antigens (10%) as well as a surface determinant associated with T cell activation (16%), i.e., possibly the receptor for interleukin 2 (IL 2). Furthermore, a relatively high plasma cell content (5%) was observed. TIL exhibited high proliferative responses to T cell mitogens (concanavalin A, phytohemagglutinin) and IL 2, but only weak responses to the B cell mitogen LPS from Salmonella typhimurium. When injected into newly hatched, MHC-identical, irradiated normal chickens, TIL induced both the production of autoantibodies and thyroid infiltration. Peripheral lymphocytes from spleen and blood and thymocytes from the same OS donors had no effect. Analysis of chemically (cyclophosphamide) bursectomized OS chickens suggested that an intact B cell system was not obligatory for the induction of SAT. TIL from these chickens consisted of 77% T cells and less than 1% B lymphocytes, yet were capable of inducing severe thyroid infiltration upon transfer into normal recipients. These findings emphasize the importance of the T cell system in the initiation of SAT.

A monoclonal antibody (INN-CH-16) was prepared which reacts with a cell surface antigen termed chicken activated T lymphocyte antigen. This antigen is expressed on antigen- or mitogen-activated T lymphocytes and is not present on nonstimulated lymphocytes. It has an apparent molecular mass of 48-50 kDa under reducing conditions. The value of this antibody for the immunohistochemical characterization of infiltrating cells in the thyroid glands from Obese strain chickens with spontaneous thyroiditis is demonstrated.

A semiautomated modification of the membrane immunofluorescence (MF) technique was developed employing units of the Microtiter ® system. This new rapid technique, which allows the performance of several hundred samples within a few hours is exemplified on a MF test proving the specific reaction of anti-chicken bursa cell sera (ABS) and antichicken thymus cell sera (ATS) on bursa anf thymus cells respectively. The possible value of the new method for the further standardization of immunofluorescence is also emphasized.

Frozen sections of chicken lymphoid organs were examined for lymphocyte surface antigens by antisera to T and B lymphocytes (ATS;ABS), and for the presence of immunoglobulin (Ig) G Fc and complement receptors (FcR;CR) by hemadsorption with sheep erythrocytes (E) coated with chicken IgG(EA), and E coated with rabbit IgG and chicken complement (EAC). In the spleen FcR positive cells were confined to the periellipsoidal sheaths and the germinal centers. CR positive cells were found in the same spleen areas, as well as in the medulla of bursal follicles. These lymphoid areas reacted strongly with ABS, but they also stained with neutral alpha-naphthyl butyrate esterase, and phagocytosed carbon particles were found in the periellipsoidal sheaths. Furthermore, in vivo treatment with cyclophosphamide, which resulted in pronounced B-lymphocyte depletion, did not affect FcR activity, but reduced CR activity significantly. These data indicate that the FcR activity demonstrated in tissue sections is mainly confined to mononuclear phagocytes, while the CR positive cells are mainly B lymphocytes.

Basal plasma levels of corticosterone and corticosteroid-binding globulin (CBG) have been investigated in Obese strain (OS) chickens afflicted with spontaneous autoimmune thyroiditis (SAT). Corticosterone was determined radioimmunologically, and CBG by using a highly sensitive radioligand saturation assay. OS chickens displayed total corticosterone levels not different from healthy normal White Leghorn (NWL) chickens. CBG, however, was found to be twice as high in OS chickens as compared with their healthy counterparts, irrespective of sex or age. This quantitative difference in the CBG level is not compensated for by either altered affinity or specificity of the molecule. Furthermore, no differences were found in the response of OS and NWL lymphocytes to the suppressive effect of glucocorticoids in vitro. We therefore assume that OS animals are deficient in free, hormonally active corticosterone. An additional indication for such a diminished glucocorticoid tonus was that in vivo treatment of OS chickens with glucocorticoid hormones, thus increasing the free and active hormone fraction, normalizes the T cell hyperreactivity and significantly reduces thyroid infiltration. Possible pathophysiological implications of a diminished glucocorticoid tonus for spontaneous autoimmunity, as well as possible explanations for the beneficial effects of glucocorticoid treatment on the development of SAT, are discussed.

Antisera prepared in rabbits and turkeys against chicken brain were tested in membrane immunofluorescence and lymphocytotoxicity tests for their reactivity with thymocytes and cells from the bursa of Fabricius of normal White Leghorn chickens. In contrast to the findings in mice and other mammals, these antisera did not afford any specific reaction with thymus cells after exhaustive absorptions of species specific antibodies with cells from various tissues. However, absorbed rabbit antisera could be shown to react specifically with cells from the granulocytic series in the bone marrow and, to a lesser extent, in the peripheral blood of chickens.

This paper describes a first attempt to correlate morphological data of chicken thrombocytoid cells obtained by phase contrast microscopy with the expression of surface determinants as recognized by heterologous anti-chicken lymphocyte sera. The following three morphological types of mononuclear cells in the peripheral blood of chickens have been distinguished: (I) small round cells, (II) small star shaped cells with short pseudopodia; both these types resembling lymphoid cells, and (III) platelet-like cells with the capacity for instantaneous adhesion and subsequent spreading, i.e., “chicken thrombocytes”. Fluid transitions of cells type I to type III have been observed to occur in earlier studies. In a combined phase contrast and membrane immunofluorescence assay on living cells using turkey anti-bursa cell and anti-thymus cell sera (ABS and ATS) and a rabbit anti-chicken immunoglobulin serum, cells of type I and II both turned out to be positively stained in 95% with ATS, whereas the vast majority (98%) of thrombocytoid cells reacted with ABS. The impact of these first data for a possible relationship between chicken B cells and thrombocytes will be discussed.

Spontaneous autoimmune thyroiditis of OS chickens is associated with a marked hyperreactivity of the T cell system. The purpose of the present study was to investigate the underlying regulatory mechanisms. Co-cultivation experiments between Con A-stimulated OS and NWL lymphocytes in communicating cultures revealed soluble regulatory factors to be responsible for the observed functional differences: the high proliferative response to Con A and hyperproduction of IL 2 of OS cells was found to be due to a deficiency in the conditioned medium of dialyzable inhibitory factor(s) that regulate IL 2 secretion of NWL lymphocytes. Furthermore, sera of young NWL chickens were found to profoundly inhibit the IL 2-promoted lymphoblast proliferation. This IL 2 antagonizing activity is lost with age (3 to 6 yr) and was found to be significantly diminished in OS birds throughout ontogeny, thus pointing to possible parallels between immune regulatory dysfunction in autoimmunity and in physiologic aging. Both enhanced T cell response and the defect in serum suppressor were inherited by (OS X CB)F1 animals, indicating that these two aberrations may be related to each other.

Thyroid glands of Obese strain (OS) chickens with spontaneous hereditary autoimmune thyroiditis were studied by direct immunofluorescence (DIF) with an anti-chicken immunoglobulin–FITC conjugate for local immunoglobulin (Ig) production in plasma cells and germinal centres. Many plasma cells and most of the germinal centres showed positive staining in DIF. The Ig property of this stained material was verified by DIF blocking and indirect immunofluorescence (IIF) tests with specific unlabelled anti-chicken Ig sera. In a chronological DIF study of thyroid glands from OS chickens aged 1–18 weeks, Ig-producing plasma cells could be already detected in the 1st week of life. DIF tests with TRITC-labelled chicken thyroglobulin revealed positive staining of plasma cells with preferential localization in close proximity to, or even between, follicular epithelial cells, suggesting the anti-thyroglobulin autoantibody nature of at least some of the locally produced Ig.

This paper summarizes data obtained in our laboratory on the demonstration of receptors for IgG-Fc (FcR) and complement (CR) on mononuclear cells of the fowl. A clearcut distinction of these two structures on spleen cells was achieved in rosette assays using SRBC coated with rabbit IgG as indicator cells which bind avian complement, but are not bound by the FcR. The tissue distribution and localization of FcR and CR positive cells was studied in mixed hemadsorption assays on sections of both central (bursa, thymus) and peripheral (spleen) lymphoid organs from normal chickens, as well as lymphocytic infiltrated thyroid glands from animals of the Obese strain (OS) afflicted with spontaneous autoimmune thyroiditis. The possible significance of both receptors in the pathogenesis of this autoimmune process is discussed.

The disturbed homeostasis of the immune system in Obese strain (OS) chickens with spontaneous autoimmune thyroiditis consists in a general T cell hyperreactivity (concanavalin A hyperresponsiveness, interleukin 2 (IL 2) hypersecretion), particularly expressed by those lymphocytes which infiltrate the diseased thyroid gland. This abnormality has been attributed to a defective regulation of both IL 2 production and IL 2 function by low m.w. factors, which are present in serum and splenocyte culture supernatants of normal chickens, but deficient in the OS. In the present study we identified the cellular origin of IL 2 antagonistic activity as a nonlymphoid, adherent cell. Suppressor factor production in vitro was confined to the plastic adherent fraction of spleen cells and preincubation of splenocytes with nylon wool, silica particles, or carbonyl iron significantly reduced the nonspecific suppressive activity of the culture supernatant. Kinetic studies revealed the defect in nonspecific suppression to entail prolonged IL 2 production by concanavalin A-activated OS spleen cells. In vivo treatment of normal White Leghorn chickens with silica led to a decrease in suppressive serum activity down to the OS level, whereas neither neonatal thymectomy nor bursectomy had any effect. The defective suppressor factor production in autoimmune chickens appeared to be due to a functional, but not numeric defect of macrophages as revealed by phenol red staining. The possibility that this aberration in adherent cell function might be a secondary phenomenon to the recently described reduced corticosterone tonus in OS chickens was excluded by in vivo substitution with exogenous glucocorticoids which did not normalize the suppressor defect in serum or in conditioned medium. Finally, we present evidence that T lymphoblasts from OS animals are less susceptible to IL 2 antagonistic regulation than normal cells, which possibly further contributes to the T cell hyperfunction of this autoimmune strain.

The enhanced T cell reactivity (ConA hyperresponsiveness and IL 2 hypersecretion) of spleen lymphocytes of Obese strain (OS) chickens with spontaneous autoimmune thyroiditis has recently been shown to be due to a defect in macrophage-derived non-specific suppressor factors that regulate IL 2 secretion and IL 2-promoted T lymphoblast proliferation in normal healthy animals. In the present study, we present several lines of evidence that the increased T cell response of peripheral blood lymphocytes (PBL) of OS chickens is due to mechanisms entirely different from the described dysregulation of splenic T cells: 1) In contrast to the splenic macrophages, peripheral blood monocytes of OS animals are not deficient in the production of IL 2 antagonistic activity (IAA); 2) therefore, cocultivation of PBL from OS and Normal White Leghorn (NWL) chickens in communicating culture chambers did not abrogate the difference in Con A response as previously observed with spleen lymphocytes. 3) Immunofluorescence with a monoclonal antibody (INN CH 16) against the chicken IL 2 receptor revealed enhanced numbers of mitogen activatable T cells in OS PBL but not OS spleen lymphocytes. 4) After prolonged Con A stimulation of PBL, OS and NWL lymphoblasts did not differ from each other in functional aspects. In contrast to this, Con A lymphoblasts from OS spleens exhibited enhanced staining with INN CH 16 in parallel with an increased proliferative response to IL 2. Thus, the primary T cell dysfunction involved in the development of autoimmune disease in OS chickens is the result of at least two separate regulatory defects.

Chicken lymphoid organs were examined for IgGFc and complement receptors (FcR/CR) by immune adherence on frozen tissue sections. Indicator systems were sheep erythrocytes (E) coated with chicken anti-E IgG (EAch), E coated with rabbit anti-E IgG (EArab) and normal chicken serum (EAC), and FITC-labelled zymosan particles coated with chicken serum (ZyC). In the spleen, FcR and CR activity was confined to B-dependent areas, i.e. the periellipsoidal sheaths and germinal centres and the red pulp. No FcR were found in the thymic or bursal lymphoid tissue, but CR activity was observed in the medulla of bursal follicles. Chicken and turkey IgG, chicken IgGFc, and bovine serum albumin (BSA)--chicken anti-BSA complexes inhibited binding of Each. No inhibition was obtained with chicken IgGF(ab')2, IgM or albumin, or with BSA--rabbit anti-BSA complexes and human or rabbit IgG. E did not adhere to the sections, nor did EArab, EArab incubated with heat-inactivated chicken serum, or EAC complexes prepared with EArab and guinea-pig complement. The data suggest that chicken B lymphocytes and macrophages have receptors for avian IgGFc and C which can be demonstrated in tissue sections.

Antigenic challenge as well as injection of lymphokine-containing media lead to a transient increase of serum glucocorticoids, a phenomenon that has been implicated in the regulation of the specificity of immune responses. In the present study we examined the dialogue between the immune and the neuroendocrine systems in Obese strain (OS) chickens, an animal model for human Hashimoto thyroiditis. The following results were obtained: A) OS and normal White Leghorn (NWL) chickens, 5-mo-old, were immunized with sheep red blood cells followed by daily monitoring of corticosterone (CN) serum levels. Whereas in NWL animals CN serum levels markedly increase 3 to 4 days after immunization, OS animals did not respond with CN elevation. B) A single i.v. injection of conditioned medium (CM) from concanavalin A-stimulated spleen cells also led to a transient, dose-dependent peak in plasma CN (maximum after 30 min). This CN response to a given CM preparation was significantly lower in OS than in NWL animals. C) CM, whether obtained from OS or NWL splenocytes, were equally effective to stimulate CN production. D) A single i.v. injection of CM leads--concomitantly to the CN peak--to a decrease of the concanavalin A-mediated proliferative response of peripheral blood lymphocytes in both OS and NWL chickens. This suppression, however, was significantly more pronounced in NWL chickens. In summary, these data suggest a disturbance of the immune-neuroendocrine communication in OS chickens with spontaneous thyroid autoimmunity. The possible implications for the generation of "forbidden" autoimmune responses are discussed.

Optimized production conditions and a functional assay of avian T cell growth factor (TCGF) or interleukin 2 (IL-2) are described. Treatment of lymphocytes with mitogen (Con A)-coated chicken red blood cells (MRC) resulted in markedly enhanced mitogenic response and IL-2 secretion compared to stimulation with free Con A. A positive correlation (r = 0.89) was found between mitogenic response and IL-2 activity of conditioned media. Enrichment of target cells, i.e., Con A lymphoblasts, by Percoll consistently improved the sensitivity of the IL-2 assay. The half-life time of chicken IL-2 at 40 degrees C was 9.7 +/- 1.7 h, which was considerably shorter than the value obtained for murine IL-2, i.e., 53.1 +/- 8.5 h. High concentrations of conditioned media were found to contain a dialysable factor that suppressed IL-2 promoted blast proliferation. The relevance of the data for in vitro analysis of T cell function as well as for establishing T cell lines in the chicken system are discussed.