Chicken thymocyte antigen which participates in cell proliferations of thymocytes and tumour‐derived lymphoid cell lines

Regulation of early chicken thymocyte proliferation by transforming growth factor-beta from thymic stromal cells and thymocytes

We examined expression of TGF-betas in chicken thymic stromal cells and thymocytes and roles of TGF-betas in thymocyte development within the thymus. Thymic stromal cells expressed TGF-beta 2 and 3 genes but not TGF-beta 4 gene. Thymocytes showed expressions of TGF-beta 2, 3 and 4 genes and each TGF-beta gene was expressed more strongly in CD3- than CD3+ thymocytes. When anti-TGF-beta antibody was added with supernatants of stromal cells into thymocyte culture, only proliferative activity of CD3- thymocytes was enhanced and the cells in S and G2/M compartments of cell cycle increased. These results suggest that TGF-beta which is expressed in the thymus may regulate the ability of immature thymocytes to progress through the cell cycle and to differentiate to CD3+ thymocytes.

Effects of chicken thymic stromal cells on the growth and differentiation of thymocytes in vitro

We examined contact-mediated effects of chicken thymic stromal cells (TSC) on thymocyte differentiation by co-cultivation of these cell populations. The primary cultures of TSC isolated from thymus mainly have consisted of epithelial cells which were polygonal in shape, possessed long processes and expressed MHC class II antigen. When thymocytes were co-cultured with TSC, 60% to 70% of thymocytes attached to TSC and some of them engulfed underneath TSC. These attached thymocytes were CD4-CD8- and CD4+CD8+ subsets and expressed alpha/beta TCRhigh or gamma/delta TCRlow. Some of the thymocytes attaching to TSC showed an increase of intracellular and nuclear density, fragmentation of cytoplasm and nuclei, and DNA fragmentation. And also, thymocytes attaching to TSC contained a higher percentage of cycling (S and G2 + M phase) cells than nonattaching cells. These results indicate that specific subsets in thymocytes selectively bind to TSC and undergo apoptotic death or proliferation because of interaction with TSC. Chicken TSC may play an important role in thymic differentiation by direct contact within the thymus as in mammals.

Effect of tylosin tartrate on humoral immune responses in chickens

While many antimicrobial agents have been reported to cause immunosuppression in animals, macrolide antibiotics enhance the immune function. Tylosin tartrate is a macrolide antibiotic approved for the control of mycoplasmosis in poultry. The purpose of this investigation was to determine the effect of tylosin on the humoral immune functions in chickens. Three days after oral tylosin tartrate administration, 4- or 8-week-old chickens were immunized intravenously with carbolic acid-killed Brucella abortus bacterin or sheep red blood cells. Seven days (plasma antibodies titre) or 4 days (antibody forming cells) post-immunization, there was a significant increase in antibody production as well as in the numbers of antibody-producing cells in tylosin tartrate-administered chickens compared with the untreated controls. However, 3 days after tylosin tartrate administration, there was no difference in the distribution of T-lymphocyte subpopulations (CD4 or CD8 positive cells) or B lymphocytes (surface immunoglobulin positive cells) in either the peripheral blood or spleens or untreated control chickens.

Participation of a chicken thymocyte antigen in intrathymic differentiation of T cells in vivo

The participation of CETHB1 antigen in the intrathymic development of T cells was analysed in sublethally X-ray irradiated chickens and normal embryos which were inoculated with anti-thymocyte monoclonal antibody CETHB1. When chickens were given a sublethal X-ray irradiation on the day of hatchings immature thymocytes existed prominently in the thymus up to 3 weeks after irradiation. The inoculation of CETHB1 monoclonal antibody on days 14 and 18 after irradiation caused an increase of CD4- CD8- cells and a decrease of CD4+ CD8+ cells as compared to changes in control chickens. However, expression of T cell receptors CD3, alphabetaTCR, and gammadeltaTCR was not influenced. Inoculation of the monoclonal antibody on embryonic days 13 to 16 resulted in a decrease of CD4+ CD8- cells and an increase of CD4-CD8- and CD4+ CD8+ cells after hatching. Thus, the binding of CETHB1 monoclonal antibody to thymocytes can inhibit the differentiation of both CD4-CD8- and CD4+ CD8+ cells to CD4+ CD8+ and CD4+ CD8- or CD4-CD8+ cells, respectively. These results suggest that CETHB1 antigen participated in the growth and differentiation of thymocytes in the thymic microenvironment.