| graft-versus-host response | <haematology> A common and serious, complication of bone marrow transplantation where there is a reaction of donated bone marrow against a patient's own tissue. When donor lymphocytes or a graft containing lymphocytes that are immunologically competent are given to a patient that has low immunological competence, an incompatibility reaction can result. This is due to antibodies from the donor against antigens in the host. This is due to mismatch of MHC Class I antigens and can produce lymphocyte clones that will react by a variety of processes against the host and cause damage. The clinical condition can be fatal and is due to the donor's immune cells recognising the host cells as foreign. The clinical entity characterised by anorexia, diarrhoea, loss of hair, leukopenia, thrombocytopenia, growth retardation, and eventual death brought about by the graft-versus-host reaction. It can occur in either chronic or acute forms and is treatable by immunosuppressive drugs. Seen most commonly following bone marrow transplantation, acute disease is seen after 5-40 days and chronic disease weeks to months after transplantation, affecting, principally, the gastrointestinal tract, liver, and skin. Radiological appearances of the gastrointestinal tract include; thickened wall, mucosal folds thickened or effaced, increased secretions most likely to be rapid transit of GI tract, mass most likely to be focal oedema, fibrosis, hallmark: diffuse, uniform thickening of small bowel. Synonym: GVH disease. Acronym: GVHD (20 Sep 2002) |
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| cutaneous graft versus host reaction | An acute erythematous maculopapular reaction with bulla formation in the most severe cases; chronic changes may resemble lichen planus or scleroderma. (05 Mar 2000) |
| secondary host | <epidemiology> See vector. (05 Dec 1998) |
| host | An organism that is infected with or is fed upon by a parasitic or pathogenic organism (for example, a virus, nematode, fungus). The term can also be applied, loosely, to a plant supporting an epiphyte. (09 Oct 1997) |
| host cell | A cell which has been infected by a virus is known as the host cell of that virus. A cell which is used in lab techniques such as DNA cloning to receive, maintain, and allow the reproduction of recombinant DNA cloning vectors. The DNA introduced with the vector is replicated whenever the cell divides and the recombinant proteins encoded for by the plasmid are reproduced in large quantities. (13 Nov 1997) |
| host-parasite relations | The interactions between two organisms, one of which lives at the expense of the other. (12 Dec 1998) |
| host range | The range of host species or cell types which a particular virus, bacteria, or parasite is able to infect or parasitise. (09 Oct 1997) |
| host range mutant | A mutant of phage or animal virus that grows normally in one of its host cells, but has lost the ability to grow in cells of a second host type. (18 Nov 1997) |
| host restriction-modification | A bacterial system where the bacterium is able to destroy invading DNA from a bacteriophage (virus which infects bacteria) while at the same time preventing the destruction of their own DNA. The phage DNA is cleaved by a restriction enzyme made by the bacterium, the bacterial DNA is modified (usually with methylation) so that the enzyme will not destroy it. (09 Oct 1997) |
| host-vector system | A combination of a bacterial host cell (i.e. A specific strain) and a virus vector (i.e. A particular bacteriophage strain) which work well together for DNA cloning. (09 Oct 1997) |
| host versus graft reaction | The normal lymphocyte mediated reactions of a host against allogeneic or xenogeneic cells acquired as a graft or otherwise, which lead to damage or/and destruction of the grafted cells. The opposite of graft-versus-host reaction. The common basis of graft rejection. (18 Nov 1997) |
| host vs graft reaction | The immune responses of a host to a graft. A specific response is graft rejection. (12 Dec 1998) |
| dead-end host | A host from which infectious agents are not transmitted to other susceptible host's. (05 Mar 2000) |
| definitive host | <epidemiology> The host in which a parasite reproduces sexually. (05 Dec 1998) |
| disease, graft-versus-host | A reaction of donated bone marrow against a patient's own tissue. Also called GVHD. (12 Dec 1998) |