| NKCF | natural killer cytotoxic factor |
|---|---|
| NKSF | natural killer cell stimulatory factor |
| NKTR | natural killer triggering receptor |
| NS | natural science; Neosporin; nephrosclerosis; nephrotic syndrome; nervous system; neurological surger... |
| NTA | natural thymocytotoxic autoantibody; nitrilotriacetic acid; Nurse Training Act |
| natural selection | The hypothesis that genotype environment interactions occurring at the phenotypic level lead to differential reproductive success of individuals and hence to modification of the gene pool of a population. (18 Nov 1997) |
|---|---|
| immunity, natural | The capacity of a normal organism to remain unaffected by microorganisms and their toxins. It results from non-specific mechanisms such as genetic endowment, naturally occurring antiviral and bactericidal substances, phagocytosis, and constitutional factors such as body temperature, oxygen tension, and age. (12 Dec 1998) |
| killer cells, natural | Cells responsible for spontaneous cytotoxicity of a variety of tumour cells without prior immunization. These natural killer cells are found in non-immune humans and experimental animals and are thought by some to be the same as killer cells (killing by antibody-dependent cell cytotoxicity), but they can also kill in the absence of antibody. (12 Dec 1998) |