An H-2L(d) hybrid molecule with a QA-2 α-3 domain and phosphatidyl-inositol anchor is not recognized by H-2L(d)-specific cytotoxic T lymphocytes

L(d)/Q7(d), a hybrid molecule consisting of α-1 and α-2 domains from H-2L(d) and α-3 and carboxy-end components from Q7(d), was expressed on the surface of CRL-3A rat liver cells. This molecule retained serologic H-2L(d) epitopes. The Ag is attached to the cell membrane through a phosphatidyl-inositol linkage, characteristic of Qa-2 molecules. Both bulk cultured and cloned H-2L(d) alloreactive CTL as well as H-2L(d) restricted vesicular stomatitis virus-specific CTL lyse CRL-3A cells which express H-2L(d) but show little or no lytic activity on cells which express the L(d)/Q7(d) hybrid. These cells also fail to act as cold target competitors for alloreactive anti-H-2L(d) CTL. However, cells expressing L(d)/Q7(d) are not resistant to CTL mediated lysis because they can be killed in the presence of lectin. These data indicate that recognition of polymorphic class I CTL epitopes in the α-1 and α-2 domains are influenced by the structure of the carboxy-end of the molecule.