Polyunsaturated fatty acids alter the rules of engagement

This study is the first report of the effect polyunsaturated fatty acids have on the expression of human leukocyte antigen (HLA) class I on the surface of antigen-presenting cells. Arachidonic acid (AA) and docosahexenoic acid (DHA) decreased expression of HLA class I on the surface of B lymphoblasts and this was associated with decreased lysis of those cells by cytotoxic T lymphocytes. AA and DHA decreased surface appearance of new class I molecules by slowing their flow from the endoplasmic reticulum to the Golgi. AA and DHA treatment of target B lymphoblasts also decreased the ability of cytotoxic T lymphocytes to form conjugates with them, suggesting an impairment of the close interaction between the antigen-presenting cell and T lymphocyte that is independent of HLA class I expression. AA and DHA-induced inhibition of HLA class I trafficking highlights a novel mechanism by which fatty acids affect antigen presentation.