Increased cytolytic T lymphocyte activity and decreased B7 responsiveness are associated with CD28 down-regulation on CD8 + cells from HIV-infected subjects. - Vingerhoets,H.H.; Vanham,G.L.; Kestens,L.L.; Penne,G.G.; Colebundem,R.L.; Vandenbruaene,M.J.; Goeman,J.; Gigase,P.L.; De Boer,M.; Ceuppen,J.L. (Clin Exp Immunol, 1995)