Translating cell biology in vitro to immunity in vivo

The elimination of pathogens and pathogen-infected cells initially rests on the rapid deployment of innate immune defences. Should these defences fail, it is the lymphocytes--T cells and B cells--with their antigen-specific receptors that must rise to the task of providing adaptive immunity. Technological advances are now allowing immunologists to correlate data obtained in vitro with in vivo functions. A better understanding of T-cell activation in vivo could lead to more effective strategies for the treatment and prevention of infectious and autoimmmune diseases.     

Quantifying cell binding kinetics mediated by surface-bound blood type B antigen to immobilized antibodies

Cell adhesion is crucial to many biological processes, such as inflammatory responses, tumor metastasis and thrombosis formation. Recently a commercial surface plasmon resonance （SPR）-based BIAcore biosensor has been extended to determine cell binding mediated by surface-bound bio- molecular interactions. How such cell binding is quantitatively governed by kinetic rates and regulating factors, however, has been poorly understood. Here we developed a novel assay to determine the binding kinetics of surface-bound biomolecular interactions using a commercial BIAcore 3000 bio- sensor. Human red blood cells （RBCs） presenting blood group B antigen and CM5 chip bearing immo- bilized anti-B monoclonal antibody （mAb） were used to obtain the time courses of response unit, or sensorgrams, when flowing RBCs over the chip surface. A cellular kinetic model was proposed to correlate the sensorgrams with kinetic rates. Impacts of regulating factors, such as cell concentration, flow duration and rate, antibody-presenting level, as well as pH value and osmotic pressure of sus- pending medium were tested systematically, which imparted the confidence that the approach can be applied to kinetic measurements of cell adhesion mediated by surface-bound biomolecular interactions. These results provided a new insight into quantifying cell binding using a commercial SPR-based BIAcore biosensor.     

Cell-mediated immunity to Theileria-transformed cell lines.

In East and Central Africa the protozoan parasite Theileria parva causes a disease of cattle called East Coast fever (ECF). In Kenya alone between 60,000 and 85,000 cattle die from ECF every year. Infected animals can recover from ECF either naturally or after treatment with tetracyclines or menoctone and are subsequently able to resist challenge with the homologous strain of parasite. That this acquired resistance is due to cell-mediated rather than humoral immunity has been suspected but never decisively shown. A major difficulty in studying immunity to ECF has been the lack of inbred animals for studying Theileria-specific immunity in the absence of allogeneic histocompatibility barriers. We have avoided this problem by measuring cell-mediated immune responses in a syngeneic system in vitro. Unidirectional mixed lymphocyte cultures (MLC) were set up using bovine peripheral blood lymphocytes (PBL) as responder cells and autologous cell lines transformed in vitro by T. parva as stimulator cells. In these cultures, DNA synthesis was induced in PBL from both normal and Theileria-immune animals. However, cytotoxic lymphocytes were induced only in cultures containing responder lymphocytes from Theileria-immune cattle. The results show that Theileria-transformed cells express antigens which are recognized by effector cells and provide evidence that cell-mediated cytotoxic mechanisms function in immunity to ECF.     

十种中草药对雏沙门氏菌的体外抑菌试验

采用琼脂平板打孔法、牛津杯法和药敏片法,检测鸡矢藤、地骨皮、白头翁、大青叶、蒲公英、五味子、乌梅、艾叶、黄连、丹参10种中草药对雏沙门氏菌的体外抑菌效果,并从中筛选具有较好体外抑菌作用的单味中草药。结果表明,五味子和乌梅对雏沙门氏菌的抑菌效果敏感性较强,丹参和黄连的敏感性一般,其他6种中草药均不敏感。试验结果表明,五味子和乌梅等对雏沙门氏菌具有一定的抗菌作用,且不同的中草药抑菌效果不同。该研究为临床治疗鸡白痢以及开发中草药制剂提供了依据。     

Cytotoxic T-cell immunity to virus-infected non-haematopoietic cells requires presentation of exogenous antigen

Cytotoxic T lymphocytes (CTLs) are thought to detect viral infections by monitoring the surface of all cells for the presence of viral peptides bound to major histocompatibility complex (MHC) class I molecules. In most cells, peptides presented by MHC class I molecules are derived exclusively from proteins synthesized by the antigen-bearing cells. Macrophages and dendritic cells also have an alternative MHC class I pathway that can present peptides derived from extracellular antigens; however, the physiological role of this process is unclear. Here we show that virally infected non-haematopoietic cells are unable to stimulate primary CTL-mediated immunity directly. Instead, bone-marrow-derived cells are required as antigen-presenting cells (APCs) to initiate anti-viral CTL responses. In these APCs, the alternative (exogenous) MHC class I pathway is the obligatory mechanism for the initiation of CTL responses to viruses that infect only non-haematopoietic cells.     

The cell-cycle regulated proliferating cell nuclear antigen is required for SV40 DNA replication in vitro

Cell-free extracts prepared from human 293 cells, supplemented with purified SV40 large-T antigen, support replication of plasmids containing the SV40 origin of DNA replication. A cellular protein (Mr approximately 36,000) that is required for efficient SV40 DNA synthesis in vitro has been purified from these extracts. This protein is recognized by human autoantibodies and is identified as the cell-cycle regulated protein known as proliferating cell nuclear antigen (PCNA) or cyclin.