There are multiple definitions:
natural killer(English)
- effector lymphocyte of the innate immune system that controls several types of tumors and microbial infections by limiting their spread and subsequent tissue damage
- Immunology, Regulation / control
- https://doi.org/10.1038/ni1582
neurokinin(English)
- a family of neurotransmitters in the body which consist of three neuropeptides- p, A and B which have been linked to emotion and pain perception
- NK1
- Neurology, Emotional aspects, Pain
- https://doi.org…1002/onco.13888
- https://psychol…org/neurokinin/