CD8<Superscript>+</Superscript>, HLA-unrestricted,cytotoxic T-lymphocyte line against malignant melanoma

A CD8⁺ cytotoxic T lymphocyte (CTL) line was derived from the peripheral blood mononuclear cells of a patient with primary melanoma. The CD8⁺ CTL line specifically lysed the autologous primary melanoma cells and not the natural killer cell-sensitive K562 cells or lymphokine activated killer cell-sensitive DAUDI cells. When a large panel of human leukocyte antigen (HLA)-matched and -unmatched allogeneic melanoma, glioma, breast and colorectal carcinoma cells was tested as targets in cytolysis assays, 4 HLA-matched and two HLA-unmatched allogeneic metastatic melanoma lines were lysed by the CD8⁺ CTL. Lysis of autologous and allogeneic melanoma cells was dependent on the effector-to-target cell ratio. Lysis of autologous melanoma cells was not blocked by anti-HLA class I or class II antibodies, confirming that the cytolytic activity of the CD8⁺ CTL was HLA-unrestricted. CTL lysis of autologous melanoma cells was CD3 (T cell receptor) dependent and FAS-FAS-L, and CD1 independent. Identification of the melanoma-associated antigen recognized by the HLA-unrestricted CTL may provide a vaccine for a broad population of melanoma patients.     

Detection of HLA class II-dependent T helper antigen using antigen phage display

Major histocompatibility complex (MHC) class II-dependent antigens not only activate CD4+ T helper (Th) cells, but also cytolytic T lymphocytes and effector cells of the innate immune system. These antigens therefore are candidate vaccines against cancer and infectious agents. We have developed a novel approach using a model antigen, tetanus toxoid (TT), which provides the basis for the establishment of a novel strategy of cloning Th antigens. In the TT model system, a cDNA library encoding part of the TT light chain which contained a TT-associated Th epitope recognized by TT-specific Th clones was displayed on a phage vector (TT-phage) and presented to TT-specific Th cells by autologous Epstein-Barr virus-transformed B cells (APC). These TT-phages were able to specifically activate two different TT-specific CD4+ Th cell lines as demonstrated both in [3H]thymidine incorporation and cytokine release assays. Th cell stimulation by TT-phages was significant at a ratio of one TT-phage in 50 irrelevant phages. The described approach provides the basis for the development of a novel strategy of cloning MHC class II-dependent Th antigens, using available Th cells. This strategy has several potential advantages over existing antigen cloning methods or biochemical peptide isolation.     

Mast cell tryptase may modulate endothelial cell phenotype in healing myocardial infarcts

Mast cells and macrophages infiltrate healing myocardial infarcts and may play an important role in regulating fibrous tissue deposition and extracellular matrix remodelling. This study examined the time-course of macrophage and mast cell accumulation in healing infarcts and studied the histological characteristics and protease expression profile of mast cells in a canine model of experimental infarction. Although macrophages were more numerous than mast cells in infarct granulation tissue, macrophage density decreased during maturation of the scar, whereas mast cell numbers remained persistently elevated. During the inflammatory phase of infarction, newly recruited leucocytes infiltrated the injured myocardium and appeared to be clustered in close proximity to degranulating cardiac mast cells. During the proliferative phase of healing, mast cells had decreased granular content and were localized close to infarct neovessels. In contrast, macrophages showed no selective localization. Mast cells in healing canine infarcts were alcian blue/safranin-positive cells that expressed both tryptase and chymase. In order to explain the pro-inflammatory and angiogenic actions of tryptase--the major secretory protein of mast cells--its effects on endothelial chemokine expression were examined. Chemokines are chemotactic cytokines that play an important role in leucocyte trafficking and angiogenesis and are highly induced in infarcts. Tryptase, a proteinase-activated receptor (PAR)-2 agonist, induced endothelial expression of the angiogenic chemokines CCL2/MCP-1 and CXCL8/IL-8, but not the angiostatic chemokine CXCL10/IP-10. Endothelial PAR-2 stimulation with the agonist peptide SLIGKV induced a similar chemokine expression profile. Mast cell tryptase may exert its angiogenic effects in part through selective stimulation of angiogenic chemokines.     

Slip of rabbit striated muscle in rigor or AMPPNP

Summary Single glycerol-extracted rabbit psoas muscle fibres have been slowly extended either in rigor or in the unhydrolysable ATP analogue AMPPNP, and their sarcomere length, sarcomere structure and tension measured. The length of regularly arrayed sarcomeres, measured by optical diffraction, increased continuously as the muscle was stretched; the maximum sarcomere extension seen was approximately 6%. In the electron microscope sarcomeres from extended muscle fixed in rigor or AMPPNP remained regular in their internal structure, without rupture or obvious lengthening around the Z line. During steady extension at 0.024% per min the tension in the muscle fibre rose until it reached a limiting value [T _m ] when the sarcomeres had stretched by 0.8–1.6% and then remained constant with continued extension, while the sarcomeres continued to stretch. Provided that a novel form of preparation of the glycerol-extracted fibres was employed,T _m in rigor was a large fraction of the tension expected from an active isometric muscle fibre. In the presence of AMPPNPT _m was reduced by a factor of 2 to 3. Step extension by 0.08% at 5-min intervals gave the same pattern of mechanical response with similar values ofT _m . The isometric tension decay in the interval between the steps was very rapid at first and slowed continuously until the next step. The average speed of tension fall between 30 and 300 s after stretch was measured at each step and plotted relative to the tension in the muscle. The relationship approached linearity, although with a significant upward curvature at high tension. The proportionality constant of the rate of tension fall to tension was 4.5×10^–4 s^–1 in rigor and 9×10^–4 s^–1 in AMPPNP. These values are less than the apparent dissociation rate constants for acto-subfragment-1 or acto-heavy meromyosin under similar conditions (Marston, 1982). These results indicate that interfilament slip does occur in rabbit skeletal muscle both in rigor and in AMPPNP, but that it is much slower that that predicted from the behaviour of the isolated proteins, as if the myosin heads interacted so as to obstruct their detachment.     

Wild-type p53 is not sufficient for serum starvation-induced apoptosis in cancer cells but accelerates apoptosis in sensitive cells

According to the conflicting growth signal model, cells that are driven to proliferate by certain oncogenes undergo apoptosis but not growth arrest upon withdrawal of growth factors. However, we found that the majority of human cancer cell lines continued to proliferate and did not undergo apoptosis following serum withdrawal. As an exeption, wild-type (wt) p53-expressing HCT116 human colon cancer cells underwent apoptosis within 24-36 h of serum deprivation. p53 degradation in human papilloma virus EG-expressing HCT116 cells led to enhanced survival that was not due to growth arrest. These results are consistent with a role for p53 in starvation-induced death in HCT116 cells. However, other cell lines did not undergo apoptosis despite their expression of wt p53. Thus, H460 cells (wt p53) were resistant to starvation-induced death but introduction of the adenovirus EIA oncoprotein induced p53 and also increased sensitivity to serum withdrawal. p53 was not stabilized by E1A and resistance to starvation-induced cell death was observed in E6-expressing H460 cells. These results suggest that although p53 contributes to starvation-induced apoptosis in sensitive (HCT116 and E1A-expressing H460) cancer cell lines, most cancer cells survived despite the presence of wt p53. We conclude that naturally selected human cancer cell lines suppress apoptosis due to conflicting growth signals.     

Mental health care in Cambodia

An effort is being made in Cambodia to involve grass-roots personnel in the integration of the care of the mentally ill into a broad framework of health services. This undertaking is examined with particular reference to the work of the Transcultural Psychosocial Organization.