A differential molecular biology search for genes preferentially expressed in functional T lymphocytes: the CTLA genes.

One approach to the isolation of molecules involved in T cell-mediated cytolysis stems from the postulate of a possible correlation between molecular phenotype and molecular functional involvement. Accordingly, CTL-specific molecules have been looked for, using a strategy based on the differential screening of a subtracted cDNA library. This led to the isolation and characterization of the following structures, expressed mostly (but no exclusively) in CTLs and inducible upon lymphocyte activation: CTLA-1 and CTLA-3 (serine-proteases), CTLA-4 (a member of the Ig superfamily) and CTLA-2 alpha and beta (homologues to the proregion of cysteine-proteases). The theoretical and practical limitations and the prospects of this type of approach are discussed.