Pyridoxine deficiency and cytotoxicity of T lymphocytes in vitro.

The effect of pyridoxine deficiency on the proliferation and cytotoxicity of BALB/c mouse lymphocytes stimulated in vitro with irradiated spleen cells from C3H mice was studied. Cytotoxicity was measured by Na⁵¹CrO₄ release from L cells which have the same histocompatibility loci as C3H mouse cells. Pyridoxal-5′-phosphate (PLP) content in the spleen and liver of pyridoxine-deficient animals was determined with Escherichia coli B/1 t7A apotryptophanase. Maintenance of animals on a pyridoxine-deficient diet for 1 to 3 weeks affected neither proliferation of lymphocytes in vitro nor their cytotoxicity. Lymphocytes from mice fed a pyridoxine-deficient diet for 5 to 6 weeks had a reduced capacity to respond to foreign lymphoid cells in vitro. The Cytotoxicity of these lymphocytes was also significantly decreased. PLP, but not pyridoxal, added directly to the medium in vitro partially restored the impaired functions of T lymphocytes.     

Ultrastructure and antigens in differentiation of thymus lymphocytes in human embryogenesis]

Thymus lymphocytes of 7--8-week human embryos have nuclei of irregular form with 1--3 distinct nucleoli characterized by absence of compact chromatin or heterchromatin. The electron-dense cytoplasm of these cells contains polysomes and an insignificant number of mitochondria. No receptors to sheep red blood cells and T antigen are revealed on their surface. In 11--12-week human embryos one can observe a decrease in the size of thymus lymphocytes, appearance of heterochromatin in their nuclei and receptors to sheep red blood cells (79%), and T antigen (60%) on the cell surface. Subsequently the quantity of compact chromatin in thymus lymphoid cells increases, and the cells acquire definitive properties and structure.     

Carbon nanotubes enhance cytotoxicity mediated by human lymphocytes in vitro

With the expansion of the potential applications of carbon nanotubes (CNT) in biomedical fields, the toxicity and biocompatibility of CNT have become issues of growing concern. Since the immune system often mediates tissue damage during pathogenesis, it is important to explore whether CNT can trigger cytotoxicity through affecting the immune functions. In the current study, we evaluated the influence of CNT on the cytotoxicity mediated by human lymphocytes in vitro. The results showed that while CNT at low concentrations (0.001 to 0.1 μg/ml) did not cause obvious cell death or apoptosis directly, it enhanced lymphocyte-mediated cytotoxicity against multiple human cell lines. In addition, CNT increased the secretion of IFN-γ and TNF-α by the lymphocytes. CNT also upregulated the NF-κB expression in lymphocytes, and the blockage of the NF-κB pathway reduced the lymphocyte-mediated cytotoxicity triggered by CNT. These results suggest that CNT at lower concentrations may prospectively initiate an indirect cytotoxicity through affecting the function of lymphocytes.     

Role of an insoluble thymus fraction in the differentiation of T lymphocytes]

An insoluble thymic fraction, free of both thymocytes and thymic hormone, was injected intraperitoneally to C57B1/6 mice. Following this injection, marked changes were noted in thymocyte populations: these consisted mainly in a significant increase of subcapsular prothymocytes, peaking at day 7. These observations were made by histological examination and confirmed by a study of physical characteristics of thymocyte populations. The possibility that this insoluble thymic fraction might have a biologically active component responsible for prothymocytes recruitment is examined.     

The differentiation of T lymphocytes. I. Proliferation kinetics and interrelationships of subpopulations of mouse thymus cells

Differential quantitative cytotoxic assays were used to distinguish the major high θ population of mouse thymus from the minor low θ subpopulation. The low θ cells were isolated in good yield by killing all high θ cells with controlled anti-θ and complement treatment, followed by a damaged cell removal step. A third population of labile cells, subject to rapid death in culture, was distinguished as a variable component within the high θ category. The corticosteroid sensitivity and anatomical location of these subpopulations was briefly considered. Large and medium sized dividing lymphocytes were studied by pulse labeling with tritiated thymidine, followed by radio-autography of separated subpopulations. Both the high θ and low θ categories included large dividing cells. Kinetic studies under conditions of continuous labeling were used to explore precursor-product relationships among the small thymocytes. Both low θ and high θ small lymphocytes showed continuous and close to linear accumulation of labeled cells, with no evidence for a marked lag in labeling. The turnover time of high θ small lymphocytes was three–four times that of low θ elements. The results suggest largely independent pathways are involved in the development of the two antigenically defined subpopulations. They do not support a direct transfer of “immature” high θ, TL positive small thymocytes in mature, active, low θ,TL negative cells. Some alternative models of T cell development are discussed.     

Chromatin degradation during the exposure of thymus lymphocytes in vitro to differentiation inducers and gamma irradiation

Chemical inductors of differentiation were shown to cause chromatin degradation in thymus lymphocytes. This process was prevented by the protein synthesis inhibitors. The fragments formed after the effect of chemical differentiation inductors on thymocytes were fully identical to chromatin internucleosome degradation products formed in the exposed cells. Chromatin degradation under the effect of chemical differentiation inductors was most pronounced in a more radiosensitive thymocyte fraction.     

Nonspecific cytotoxicity of spleen cells and the specific cytotoxic action of thymus-derived lymphocytes in vitro

Spleen cells removed from immunized mice specifically kill allogeneic lymphoma cells in vitro, but in the presence of specific antigen nonspecific target cell growth inhibition also occurs. Only the specific target cell killing was found to be θ-sensitive, the nonspecific cytotoxicity was caused by a population of θ-resistant, adherent, and AMS-sensitive cells. Nonspecific cytotoxic effects were caused by spleen cells from normal mice after incubation with endotoxin, and these effects were inhibited by removal of the adherent cells.     

Effect of histamine and histamine antagonists on natural and antibody-dependent cellular cytotoxicity of human lymphocytes in vitro

The in vitro effect of histamine and its antagonists, cimetidine and clemastine fumarate, on natural killer (NK) and antibody-dependent cellular Cytotoxicity (ADCC) activities of human lymphocytes was investigated. The histamine 1 (H1) antagonist, clemastine fumarate, and the histamine 2 (H2) antagonist, cimetidine, but not histamine alone, inhibited the NK and ADCC activities of lymphocytes when added directly to the mixture of effector and target cells in a ⁵¹Cr-release assay. This inhibition was proportional to the concentration of drugs added and was observed at various effector to target ratios against several targets. H1 and H2 antagonists also inhibited NK activities of T cells as well as Percoll-separated, NK-enriched effector cells. The inhibition was significantly reversed by histamine. In target binding assays, clemastine fumarate and cimetidine also decreased the target binding capacity of effector lymphocytes. Further, PBL precultured with histamine (10^?3–10^?4M) for 24 hr showed a significant decrease in their NK and ADCC activities. In coculture experiments, PBL precultured with histamine suppressed the NK activity of normal autologous effector lymphocytes. PBL precultured with histamine showed an increased number of OKT8⁺ cells, as estimated using monoclonal antibodies. The suppression of Cytotoxicity was not due to either direct toxicity, steric hindrance, crowding, or cell death, but by functionally viable suppressor cells. An immunoregulatory role for histamine in NK and ADCC reactions is proposed.     

Natural cell-mediated cytotoxicity in normal human peripheral blood lymphocytes and its in vitro boosting with BCG

Summary Natural cell-mediated cytotoxicity (NCMC) against K-562 human erythroleukemic cells was monitored in an overnight chromium release assay using normal human peripheral blood lymphocytes (PBL) as effector cells. Two hundred and ten normal individuals were tested from 3 to 24 times over a period of 3 years. The level of NCMC was shown to vary from 4% to 46% lysis at an effector-to-target cell ratio of 5/1; males had higher levels of activity than females (P<0.001). A group of individuals with low natural killer (NK) cell activity (below the 90% tolerance limit) was identified in replicate experiments and 60% of them were young women (ages 20–39). In vitro boosting of NK activity with Bacillus Calmette-Guérin (BCG) was also studied; overall, 56% of normal individuals responded positively to BCG. There was a significant (P<0.0001) correlation between the unstimulated level of NCMC and the in vitro boosting with BCG, as 63% of individuals with a normal level of NK activity could be boosted as against only 19% of persons with low NK activity. We have also established the in vivo relevance of this in vitro test by determining the degree of correlation between responses to in vitro boosting with BCG and a positive or negative reaction in a hypersensitivity skin test using 5 IU of PPD (purified protein derivative of BCG). Our results indicate that NCMC is an individual trait that varies little under physiological conditions, and that the response to BCG is a characteristic property of the effector lymphocyte, depending primarily on the unstimulated level of NCMC.     

Interaction of thymus lymphocytes with histoincompatible cells. IV. Mixed lymphocyte reactions of activated thymus lymphocytes

CS7BL-activated CBA T cells (T.TDL) were obtained by thoracic duct cannulation of (CBA × C57BL)F₁ mice 4 days after heavy irradiation and injection of CBA thymus cells. T.TDL behaved differently from the TDL of normal CBA mice in unidirectional mixed lymphocyte culture in a number of respects: (a) the response of T.TDL was directed specifically against C57BL antigens, whereas normal TDL responded to both C57BL and BALB/c antigens; (b) the response of T.TDL was rapid but transient compared to that of TDL; (c) whereas only approximately 3% of TDL synthesized DNA specifically in response to C57BL antigens, as many as 25% of C57BL-activated T.TDL responded to these antigens. Evidence is presented which suggests that the T.TDL have a very limited capacity to proliferate. Most of the cells which responded to antigen synthesized DNA without subsequently entering mitosis.     

Stimulation of expression of IgM and IgG receptors on human thymus lymphocytes after treatment with lactoferrin in vitro

It was established by immunofluorescence that lactoferrin, one of the heteroorganic thymus antigens, can stimulate the expression of Fc mu and Fcj receptors on thymus lymphocytes. The stimulating effect of lactoferrin on T mu cells is more pronounced with the level of these cells in the thymus being low. Its effect on Tj cells seems independent of their level in the thymus and may be related to their precursor differentiation. It can be assumed that one of the functions of lactoferrin in the thymus is to influence the process of differentiation of T mu and Tj cells and to regulate their level in the thymus. Lactoferrin, like other heteroorganic thymus antigens, may take part in the functional maturation of different subpopulations of thymocytes, including T mu and Tj thymus cells.