T

Taarbaek disease Synonym for Bamble disease.

Taastrup virus An unclassified virus detected by electron microscopy in the leafhopper, Psammotettix alienus, reared on healthy Festuca gigantea plants. The particles closely resemble those of filoviruses, Marburg and Ebola viruses. The particles are straight, slightly curved or flexuous, sometimes with one end curved into a ring, with an outer diameter of 200 nm. The median length was 600-1100 nm. The resemblance to filoviruses is striking.

Lundsgaard T (1997) Virus Res 48, 35

T antigens Tumor antigens, demonstrated by immunofluorescence or CF test using sera from tumor-bearing animals, that appear in the nucleus and in some cases also in the cytoplasm of virus-induced tumor cells or cells transformed in vitro. T antigens are specific for the inducing virus, but not for cell species, and are encoded in the viral genome. In cells transformed by papovaviruses or certain adenoviruses (e.g. types 12, 18 or 31) virus is not produced, and only certain early genes are transcribed. The products of these genes act as oncogenes to transform the host cells to altered growth properties. Polyomavirus induces three T proteins: small T, middle T and large T; SV40 virus induces two: large T and small T. The analogous gene products of adenoviruses and papillomaviruses are no longer referred to as T proteins. For adenovirus they are E1A and E1B, and for papillomaviruses they are E6 and E7, named after the E (early) genes that specify them. The action of several of these transforming proteins involves binding to cell proteins that normally act as tumor suppressors, e.g. p53 and pRB (retino-blastoma) proteins. The adenovirus E1A and E1B proteins, the SV40 T antigen and the human papillomavirus E6 and E7 proteins all bind to p53 and pRB, leading to their functional inactivation. The polyoma middle T and large T proteins also target cell proteins that normally regulate cell growth; middle T binds to tyrosine kinase, phosphatidylinositol-3 kinase and phosphatase 2A; and large T binds to pRB, but not to p53.

Neil JC and Wyke JA (1998) In Virology, vol. 1 of Topley and Wilson's Microbiology and Microbial Infections, Ninth edition, edited by BWJ Mahy and L Collier. London: Arnold, p. 211

T cells Lymphocytes of thymic origin that have been through thymic processing. They bear T-cell antigen receptors (CD3) and lack Fc or C3b receptors. Major T-cell subsets are CD4+ (helper cells) and CD8+ (cytotoxic cells).

T-cell receptors Antigen-specific receptors on the surface of T lymphocytes which recognize peptides bound either to class I or class II major histocompatibility complex (MHC) molecules. Upon specific interaction of the T-cell receptor with antigen, signals are transduced through the plasma membrane, activating the T-cell to initiate cell division, secrete lymphokines (T-helper cells) or lyze its target cells (cytotoxic T-lympho-cytes).

Parham P (1992) Nature 357, 538

0 0

Post a comment