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Biomedical subjects

T J Yang

Publications and source records attributed to T J Yang.

At least 127 records · Page 7Linked to original sources
PubMedDate not supplied

Development and characterization of an IL-2-dependent bovine CD4+ lymphoblastoid T-cell line.

A bovine IL-2-dependent lymphoblastoid T-cell line (BLTC) was developed and established from peripheral blood mononuclear cells stimulated with Con A, and subpassaged in conditioned media prepared from Con A-activated bovine lymph node cells. The BLTC cell line is IL-2 dependent, requiring exogenous IL-2 either in the form of recombinant bovine or human IL-2 or conditioned media prepared from Con A-stimulated bovine lymph node cells. Conditioned media prepared from mononuclear cells from other species, such as dogs and rats, were without any stimulatory effects. The growth of these cells was lectin-independent, and monokines such as IL-1 beta and TNF-alpha, or conditioned media from LPS-stimulated macrophases failed to support their growth. Immunophenotyping showed that over 90% of the cells were CD2+, CD3+, and CD4+, 25% were CD5%, less than 2% were CD8+, and less than 2% were CD20+. The cells were negative for the gamma delta 215/300 kDa T-cell markers and the 75/110 kDa monocyte markers. The growth of these cells was inhibited by dibutyryl cAMP in the presence or absence of IL-2, and stimulated by the phorbol ester, PMA, in the absence but not in the presence of IL-2. The effects of IL-2 and PMA were blocked by the protein kinase C inhibitor, H-7, suggesting that IL-2 signaling is closely associated with the PKC activation pathway.

Animals↗
PubMedDate not supplied

Monoclonal antibody BLT-1, specific for the bovine homologue of CD5, reacts with the majority of mature T cells, a subpopulation of B cells and stimulates T cell proliferation.

Monoclonal antibody (MAb) BLT-1, an IgG2a with kappa light chains, reacted strongly with 21% of bovine thymocytes, weakly with 15% of thymocytes, with a subpopulation of peripheral blood B cells that also expressed CD20 and with peripheral blood T cells. Practically all of the reactive thymocytes were of a large cell subpopulation. By immunoprecipitation, BLT-1 was shown to recognize a membrane molecule with a molecular mass of 67 kDa. In competitive assays for lymphocyte surface binding, BLT-1 and MAb CC-29 (which had been shown previously to react with bovine CD5) blocked one another, indicating that the epitopes recognized were identical or extensively overlapping. In contrast, another CD-5-reactive MAb, CC-17, did not block BLT-1 reactivity with lymphocytes although the reactivity of CC-17 was blocked by BLT-1, suggesting partial overlap of the epitopes or steric hindrance by BLT-1 but not by CC-17. BLT-1 was able to induce proliferation of bovine lymphocytes in culture alone if monocytes were present or in the absence of monocytes synergized with PMA. The results indicate that BLT-1 recognizes an epitope of the bovine homologue of CD5 and that perturbation of the epitope by MAb binding results in signal transduction to bovine lymphocytes.

Animals↗
PubMedDate not supplied

Age-dependent changes in peripheral blood lymphocyte subpopulations in cattle: a longitudinal study.

Immunofluorescence and flow cytometric analyses were used to study the age-dependent changes in the peripheral blood lymphocyte (PBL) subpopulations in cattle. Four healthy Holstein heifer calves (A, B, C and D), 1-2 months of age, were used in this study. Sequential peripheral blood samples were collected once a month for up to 2-2.5 years, and once at approximately 4 years of age. For the first 6 months of age, the calves had similar proportions of CD2+, CD4+, CD8+ T lymphocytes, CD20+ B lymphocytes and MHC class II+ lymphocytes. From 2 months of age up to 2-2.5 years of age, all animals had similar proportions of CD5+ cells; but during the same period, animals A and B had significantly lower proportions of WC1+ gamma delta T cells than animals C and D. After 7 months of age, however, the proportions of CD2+, CD4+ and CD8+ T cells in PBL of animals A and B significantly decreased, whereas the proportions of both CD20+ B lymphocytes and MHC class II+ lymphocytes significantly increased. In contrast, the proportions of the various PBL subpopulations in animals C and D remained virtually unchanged after 7 months of age. For the first 6 months of age, all the calves showed similar absolute counts of PBL. Thereafter, the absolute counts of PBL in animals A and B significantly increased, but remained virtually unchanged in animals C and D. Throughout the study, from 1-2 months up to 2-2.5 years of age the absolute counts of CD2+, CD4+, CD8+ and WC1+ gamma delta T cells in PBL of the four animals were not significantly different from each other. Up to 6 months of age, the CD4+/ CD8+ ratio in all calves was 2.38 +/- 0.46, but significantly decreased thereafter to 1.81 +/- 0.34. However, there were no significant differences in the CD4+/CD8+ ratios among individual animals. The increase in the absolute counts of PBL in animals A and B, after 7 months of age, was due to an increase in the absolute counts of CD5+ cells, CD20+ B lymphocytes and MHC class II+ lymphocytes. Thus, changes in the percent, but not the absolute counts of T lymphocytes, were due to high percent and absolute counts of B lymphocytes, expressing the CD5 and MHC class II antigens.

Aging↗
PubMedDate not supplied

Detection of flunixin in greyhound urine by a kinetic enzyme-linked immunosorbent assay.

A two-step kinetic enzyme-linked immunosorbent assay was developed to detect the presence of flunixin in the urine of greyhound dogs. The assay system was developed using polyclonal antiflunixin antisera, a rabbit albumin-flunixin conjugate adsorbed onto polystyrene microtiter strips, and flunixin reference standards for calibration. The assay parameters were optimized and the performance characteristics were determined. The quantitative intra- and inter-run precisions (%CV) of the analysis of replicate (n = 10) flunixin-spiked urine samples were 9.9-12.5% and 10.2-13.6%, respectively. The linear dynamic range was 1-100 ng/mL, and the quantitative accuracy, as determined by calculation of percent error of measured flunixin in flunixin-spiked drug-free greyhound urine, was -16% to +14% over this range. The I50 of the ELISA was 17.3 ng/mL. The limit of detection was 25 ng/mL in greyhound urine. The reactivity in the assay system relative to flunixin (100%) was 147% for flunixin glucuronide, 25% for clonixin, and 5% for niflumic acid. The ELISA was capable of detecting total flunixin for up to 72 h in dogs administered flunixin at 0.55 mg/kg orally and up to 96 h in a dog that was administered flunixin at 1.0 mg/kg orally.

Adjuvants, Immunologic↗
PubMedDate not supplied

Size, CD4 and CD8 marker profiles and functions of lymphocyte subpopulations in mucosal-associated lymph nodes.

We analyzed phenotypic and functional characteristics of T cell populations in mucosal-associated supramammary and mesenteric lymph nodes in goats. Here we demonstrate, by flow cytometry, quantitative differences in CD4 and CD8 T cell subsets among large and small mucosal-associated lymphocyte populations and their differential regulatory activities on resident lymph node B cells stimulated with Staphylococcus aureus Cowan I or pokeweed mitogen. The CD4/CD8 T cell ratio was lower in mesenteric lymph nodes (1.46) when compared to that of supramammary lymph nodes (2.18). Analysis of large and small lymphocyte subpopulations from lymph nodes showed nearly 62% of the lymphocytes from mesenteric lymph nodes being of large cell phenotype with CD4/CD8 ratios of 1.34. In contrast, large cell subpopulations in supramammary lymph nodes showed a significantly lower number (50%) with a higher CD4/CD8 ratio of 2.05. Functionally, mesenteric lymph node T cells, isolated by nylon wool, showed heightened suppressive activity in mitogen-driven B cell proliferation responses, whereas T cells from supramammary lymph nodes were stimulatory. These findings clearly demonstrate distinctive functional properties between resident T cell populations of supramammary and mesenteric lymph nodes, suggesting that different proportions of T cell subsets in these nodes are activated and thus regulate regional immune responses via different pathways.

Animals↗
PubMedDate not supplied

Growth regulatory effects of transforming growth factor-beta 1 and interleukin-2 on IL-2 dependent CD4+T lymphoblastoid cell line.

Transforming growth factor-beta 1 (TGF-beta 1) is an immuno-modulatory cytokine which has been shown to modulate the activity of T and B cells. We show here that human TGF-beta 1 inhibited stationary cultures of IL-2 dependent CD4+ bovine lymphoblastoid T cells (BLTC) by down-regulating their IL-2 receptor (IL-2R) expression, arresting cells in the G0/G1 compartment of the cell cycle, and inducing these cells to undergo apoptosis. These events were reversed by the addition of a minimal concentration of IL-2 (2U/ml). In the presence of exogenous IL-2, TGF-beta 1 was found to augment the proliferative response of BLTC through up-regulation of IL-2R expression, allow progression of normal cell cycle, and significantly prevent apoptosis. Our data clearly show that IL-2 and TGF-beta 1, when present alone, have contrasting effects on BLTC. TGF-beta 1 down regulates events that are associated with IL-2 mediated signal. But when present together, IL-2 and TGF-beta 1 upregulate activation signals and proliferation of rapidly dividing CD4+T cells.

Animals↗
PubMedDate not supplied

Tumor infiltrating lymphocytes: CD8+ lymphocytes in canine transmissible venereal sarcomas at different stages of tumor growth.

This study utilized an in vivo tumor system (canine transmissible venereal sarcoma, CTVS) to assess wh correlation exists between tumor growth stage and phenotype of infiltrating lymphocytes. Additionally, the ability of CTVS cells to produce chemoattractants for canine lymphocytes was assessed. The CD8 subset of tumor infiltrating lymphocytes (TIL) during progressive growth, steady-state (no growth), and regression of the CTVS was determined. During progressive growth, the proportion of TIL expressing CD8 was significantly lower than that from regressing tumors (P < .001) and steady-state tumors (P < .01). Additionally, CTVS cell culture, CTVS spheroid cell culture, and CTVS spheroid/canine lymphocyte co-culture supernatants were tested for chemotactic activity for canine lymphocytes. CTVS and CTVS spheroid/canine lymphocyte co-culture supernatants both had significant chemotactic activity. Conversely, CTVS spheroid culture supernatants were negative for chemotactic activity for canine lymphocytes. These results indicate a correlation exists between the CD8 subset of TIL and clinical stage of the tumor. Also, we have shown that CTVS cells in vitro produce soluble factors that cause chemotaxis of canine lymphocytes. An understanding of the role of TIL and the ability of the tumor to attract them will be of help in designing strategies for immunomodulatory therapies for solid tumors.

Animals↗