Specificity problems, especially in immunoblot analysis, have been shown for several commercial antibodies raised against the death ligand Fas ligand (FasL) using conventional protein and/or peptide immunizations. In this work, we have optimized the development of rabbit antisera and isolated pAb against the death ligands FasL, Apo2 ligand/TRAIL and Apo3 ligand/TWEAK by cDNA intramuscular immunization. This alternative approach has generated specific pAb in all three cases, which are useful for immunoblot purposes. The present data suggest that for the production of antibodies against certain glycosylated membrane proteins, cDNA immunization could be the method of choice.