T-lymphocyte activation pathways in alcoholic liver disease

Immune system derangement in cirrhotic patients with evidence of malnutrition is a well-recognized characteristic of chronic alcohol abuse. However, in vitro studies on cellular immune function performed with lectin mitogens have produced conflicting results. The recent development of more accurate immunological techniques for studying lymphocyte transformation, that use monoclonal antibodies directed against surface structures (CD3 and CD2) involved in antigen recognition, as well in adhesion functions, prompted us to study discrete in vitro T-cell hypo-responsiveness in a series of alcoholic liver disease (ALD) patients with no evidence of malnutrition or hepatic cirrhosis. The results indicated that the CD2 pathway is markedly defective in ALD T lymphocytes, accompanied by reduced interleukin-2 (IL-2) receptor expression upon in vitro activation. This defect cannot be reversed by the addition of recombinant IL-2 (rIL-2) or rIL-1. Faulty intracellular signal transduction by protein kinase C (PKC) and defective intracellular Ca2+ mobilization may be responsible for the CD2 pathway impairment. The addition of small amounts of phorbol 12-myristate, 13-acetate, but not Ca2+ ionophore A23187, is able to overcome the defect, thereby suggesting a direct PKC involvement. The hypothesis of a direct ethanol effect on transmembrane signal transduction systems is suggested by the demonstration of an expansion of circulating virgin (naive) T cells (CD3+/UCHL1-low) that binds tyrosine phosphatase (CD45RA antigen) on their surface.