Cell culture

About: Cell culture is a research topic. Over the lifetime, 133361 publications have been published within this topic receiving 5364150 citations. The topic is also known as: cell culture techniques.

Coexpression of two distinct genes is required to generate secreted bioactive cytotoxic lymphocyte maturation factor

Abstract: Cytotoxic lymphocyte maturation factor (CLMF) is a disulfide-bonded heterodimeric lymphokine that (i) acts as a growth factor for activated T cells independent of interleukin 2 and (ii) synergizes with suboptimal concentrations of interleukin 2 to induce lymphokine-activated killer cells. We now report the cloning and expression of both human CLMF subunit cDNAs from a lymphoblastoid B-cell line, NC-37. The two subunits represent two distinct and unrelated gene products whose mRNAs are coordinately induced upon activation of NC-37 cells. Coexpression of the two subunit cDNAs in COS cells is necessary for the secretion of biologically active CLMF; COS cells transfected with either subunit cDNA alone do not secrete bioactive CLMF. Recombinant CLMF expressed in mammalian cells displays biologic activities essentially identical to natural CLMF, and its activities can be neutralized by monoclonal antibodies prepared against natural CLMF. Since this heterodimeric protein displays the properties of an interleukin, we propose that CLMF be given the designation interleukin 12.

SV40-encoded microRNAs regulate viral gene expression and reduce susceptibility to cytotoxic T cells

Abstract: MicroRNAs (miRNAs) are small (approximately 22-nucleotide) RNAs that in lower organisms serve important regulatory roles in development and gene expression, typically by forming imperfect duplexes with target messenger RNAs. miRNAs have also been described in mammalian cells and in infections with Epstein-Barr virus (EBV), but the function of most of them is unknown. Although one EBV miRNA probably altered the processing of a viral mRNA, the regulatory significance of this event is uncertain, because other transcripts exist that can supply the targeted function. Here we report the identification of miRNAs encoded by simian virus 40 (SV40) and define their functional significance for viral infection. SVmiRNAs accumulate at late times in infection, are perfectly complementary to early viral mRNAs, and target those mRNAs for cleavage. This reduces the expression of viral T antigens but does not reduce the yield of infectious virus relative to that generated by a mutant lacking SVmiRNAs. However, wild-type SV40-infected cells are less sensitive than the mutant to lysis by cytotoxic T cells, and trigger less cytokine production by such cells. Thus, viral evolution has taken advantage of the miRNA pathway to generate effectors that enhance the probability of successful infection.

Formation of bone and cartilage by marrow stromal cells in diffusion chambers in vivo.

Abstract: When freshly isolated rabbit marrow cells were cultured either in vitro or in diffusion chambers in vivo, the hemopoietic cells disappeared and there was a proliferation of the stromal cell population. The colonies formed in vitro were mainly fibroblastic, and this cell type predominated in confluent cultures. Staining for alkaline phosphatase activity and for the Von Kossa reaction was negative in in vitro cultures. However, marrow cell suspensions or fibroblasts harvested from in vitro culture of marrow cells, gave rise to a mixture of bone, cartilage and fibrous tissue in diffusion chambers implanted into the peritoneal cavity. In contrast, only a soft fibrous tissue developed from spleen fibroblasts in diffusion chambers. Differentiation of osteogenic tissue within diffusion chambers fell into two categories: (1) Formation of bone in a fibrous layer surrounding cartilage; (2) intramembranous bone formed directly within fibrous tissue unassociated with cartilage. In both cases alkaline phosphatase activity appeared before the onset of mineralization, and decreased as the first signs of mineral became apparent. The present results suggest that postnatal marrow contains osteogenic precursors with the potential to differentiate via either of the two major paths followed during skeletal development in the embryo. Clonal analysis of the marrow stromal cell population will be required to clarify whether osteo-, chondro-, and fibrogenic cells are the products of one stromal cell line modulated by the microenvironment, or whether there are distinct cell lines for each type.