The purpose of this study is to determine whether the exposure to acute and/or chronic ethanol consumption increases natural killer (NK) activity of immune effector cells. NK activity is a possible mechanism of ethanol induced liver damage. Acute exposure to ethanol has been reported by others as inhibitory of NK activity in vitro. However, we have found that chronic ethanol increases NK activity in vivo in rat pit cells, which are NK cells resident in the liver. Ethanol might be implicated in the stimulation of NK activity of immune effectors against liver cells. In this study, we have isolated pit cells (Large granular lymphocytes) from Lewis rat hepatic sinusoids, and determined an increase in their ability to bind to, and lyse specific target cells, including an endothelial cell line (SVEC4- 10), when the rats have been treated with ethanol for two weeks. Both vascular and sinusoidal endothelial cells, as well as liver parenchymal cells, are potential target cells for these NK effectors. In order to assess this finding in human immune effector cells, we will examine the NK activity of human circulating lymphocytes, in each of the following groups of patients: a- Chronic alcoholics who are still drinking; b- Chronic alcoholics recently withdrawn from dependency; c- sober alcoholics (alcoholics with no recent drinking history); and d- Normal healthy volunteers. We will measure the effector- to- target binding ratio, the effector- to- target lysing ratio, by chromium release assays. Several target cells will be utilized, including human endothelial cell lines as well as hepatoma cell lines. We will measure perforin (pore forming protein/ cytolysin) mRNA levels in the lymphocytes by molecular probing. We intend to verify the involvement of perforin as the mediator of increased NK activity, and correlate the increase in binding capacity and lysing activity with perforin mRNA levels in the effector cells. The effect of ethanol on circulating human lymphocytes has been determined, but not in correlation with perforin levels. The implication of this cytolytic protein as the specific mechanism of liver cell killing has clinical relevance in regards to the potential inhibition of liver cell damage by ethanol, as to what pertains to NK cell mediated damage.