Killer phenomenon

The determinants of the killer factor are both cytoplasmic and nuclear. In S. cerevisiae, the killer phenomenon is associated with the presence of double-stranded RNA particles, virus-Uke particles (VLP), in the cytoplasm. They are in the same category as non-infectious mycovirus. There are two kinds of VLP M and L. The M genome (1.3-1.9 kb) codes for the K toxin and for the immunity factor (R). The L genome (4.5 kb) codes for an RNA polymerase and the proteinic capsid that encapsulates the two genomes. Killer strains (K+R+) secrete the toxin and are immune to it. The sensitive cells (K R ) do not possess M VLP but most of them have L VLP. The two types of viral particles are necessary for the yeast cell to express the killer phenotype (K+R+), since the L mycovirus is necessary for the maintenance of the M type. 

NK cells possess a receptor for Fc/and this enables them to adhere to target cells coated in antibody with the resultant destruction ofthat cell. This phenomenon is known as antibody-dependent cell-mediated cytotoxicity (ADCC). This was attributed to a separate cell population known as killer (K) cells but these have now been shown to be in effect NK cells. 

Neither of these sites contains much scientific theory. A more in-depth survey of the phenomenon of pain may be found at http //www.chic.org.uk/press/releases/pain2.htm, produced by the Consumer Health Information Centre (CHIC) and Michael Gross short article The molecules of pain describes the sensation of pain and the mode(s) by which pain killers operate see Chemistry in Britain, June 2001, p. 27. 

Grimm EA, Mazumder A, Zhang HZ, Rosenberg SA. Lymphokine-activated killer cell phenomenon lysis of natural killer resistant fresh solid tumor cells by interleukin-2 activated autologous human peripheral blood lymphocytes. J Exp Med 1982 155 1823-41. 

This phenomenon, the killer factor, was discovered in S. cerevisiae but killer strains also exist in other yeast genera such as Hansemla, Candida, Kloeckem, Hanseniaspora, Pichia, Tom-lopsis, Kluyveromyces and Debaryomyces. Killer yeasts have been classified into 11 groups according to the sensitivity reaction between strains as well as the nature and properties of the toxins involved. The killer factor is a cellular interaction model mediated by the proteinic toxin excreted. It has given rise to much fundamental research (Tipper and Bostian, 1984 Young, 1987). Barre (1984, 1992), Radler (1988) and Van Vuuren and... 

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