Tumor cell rejection through terminal cell differentiation

Leukemic cells cultured in the presence of various conditioned media differentiate into macrophages. This finding suggested that the maintenance of undifferentiated state and self-renewal in vivo may be related to the inability of the host to generate an appropriate level of differentiation factor (DF). Evidence for this hypothesis was derived from experiments in vitro and in vivo with myeloid leukemia of rat. The following results were obtained: (i) in vitro, the percentage of cell differentiation at a fixed concentration of DF was inversely related to the concentration of cells; (ii) leukemic cell inoculates that were lethal to 7-day-old rats were rejected by 21-day-old rats; (iii) leukemic cells in diffusion chambers underwent differentiation in 21-day-old rats but not in 7-day-old rats; (iv) organs from 21-day-old rats contained more DF activity than those of 7-day-old rats; (v) treatment of rats with DF in diffusion chambers resulted in leukemic cell differentiation inside the chamber; and (vi) the development of leukemia in 7-day-old rats was aborted by treatment with DF. These results show that the differentiation of rat leukemia cells requires the appropriate level of DF. The proliferation of transplanted leukemia cells in 7-day-old rats goes unchecked because of inadequate generation of DF. Conversely, in the 21-day-old rats, rejection is accomplished by differentiation of the transplanted cells.     

Reciprocal control of T helper cell and dendritic cell differentiation

It is not known whether subsets of dendritic cells provide different cytokine microenvironments that determine the differentiation of either type-1 T helper (TH1) or TH2 cells. Human monocyte (pDC1)-derived dendritic cells (DC1) were found to induce TH1 differentiation, whereas dendritic cells (DC2) derived from CD4+CD3-CD11c- plasmacytoid cells (pDC2) induced TH2 differentiation by use of a mechanism unaffected by interleukin-4 (IL-4) or IL-12. The TH2 cytokine IL-4 enhanced DC1 maturation and killed pDC2, an effect potentiated by IL-10 but blocked by CD40 ligand and interferon-gamma. Thus, a negative feedback loop from the mature T helper cells may selectively inhibit prolonged TH1 or TH2 responses by regulating survival of the appropriate dendritic cell subset.     

Spectrophotometric cell sorter

A new device can physically separate cells of predetermined optical properties, from large populations of cells in suspension.     

番茄果皮与叶片光合细胞超微结构的比较

文章对番茄果实不同生长阶段果皮细胞中叶绿素含量进行了测定,并将番茄果皮细胞与成熟叶片光合细胞超微结构进行了比较观察。结果显示,番茄果皮细胞在果实不同生长阶段叶绿素含量、叶绿体结构发生变化,绿熟果期果皮细胞的叶绿素含量最高,果皮细胞含有一定数量的叶绿体,并且具有典型的的基粒片层结构。根据植物光合产物就近运输理论,果皮细胞中叶绿体形成的光合产物,能够及时地转移到果实中,供应果实的生长发育。绿熟果期果皮细胞的叶绿素含量、叶绿体、基粒数量及类囊体垛叠层数明显少于叶肉细胞,说明此时期叶片仍是番茄进行光合作用的主要器官。在果实完熟期,其外观已经由绿色变成红色,果皮细胞中的叶绿体逐步转化为有色体,类囊体基粒片层消失,叶绿体内部含有大量嗜锇颗粒,失去光合能力。     

牦牛子宫基质细胞与上皮细胞的标记物

以妊娠前后的牦牛子宫为材料,应用免疫组织化学SP法,研究波形蛋白(Vimentin)、泛角蛋白(CKs)和角蛋白7(CK7)能否成为牦牛子宫内基质细胞和上皮细胞的特异标记物.结果表明,Vimentin可作为妊娠前后牦牛子宫基质细胞标记蛋白;CKs可标记妊娠前后牦牛子宫腺上皮、腔上皮细胞和妊娠早期尿囊内层细胞;CKs和C...     

Determination of junction avidity of cytolytic T cell and target cell

A direct measurement of the avidity of the junction between a cytotoxic T lymphocyte and its target cell was achieved by using a biophysical approach. A micromanipulation technique was used to determine the force required to separate a cytotoxic T cell (human clone F1, with specificity for HLA-DRw6) from its specific target cell (JY: HLA-A2, -B7, -DR4, w6) prior to delivery of the lethal hit. The force required to separate the F1-JY pair is 1.5 X 10(4) dynes per square centimeter. This junction avidity for F1-JY pairs is 6 to 13 times greater than that for F1-F1 and JY-JY pairs; the F1-JY conjugate requires a stronger separating force and is more easily rejoined than the homologous cell pairs. This study provides an estimate of the avidity of cytotoxic T cells for their target cells and insights into the biophysical correlates of the molecular complexes formed in the interaction of cytotoxic T cells and their targets during the cytotoxic process.     

Activation-driven programmed cell death and T cell receptor zeta eta expression

Activation of spontaneously dividing T cell hybridomas induces interleukin-2 (IL-2) production, a cell cycle block, and programmed cell death. T cell hybridomas that express the T cell antigen receptor (TCR) zeta homodimer (zeta 2), but not the TCR zeta eta heterodimer, were studied. The zeta eta- cells produced little or no inositol phosphates (IP) when stimulated with antigen. In most cases the hydrolysis of phosphoinositides was also impaired after stimulation with antibody to CD3, although one zeta eta- cell produced normal concentrations of IP. The zeta eta- cells slowed their growth and secreted IL-2 in response to both stimuli. However, the zeta eta- cells did not die after activation with antigen. Since activated thymocytes also undergo programmed cell death, these results may have important implications for the role of the zeta eta.TCR in negative selection.