The FL-74 cell membrane immunofluorescence test seems to be the most sensitive method to detect seroconversion compared to ELISA and Western blotting. This may be due in part to the less stringent test conditions, which allow antibodies with lower affinity to bind to their epitopes, and in part to the fact that in the FOCMA assay the binding targets are presented in a native conformation, thus allowing a better binding of conformation-specific antibodies. Induction of cytotoxic T-cells or virus-neutralizing antibodies by oral low dose infection, or Th1 cytokine expression that might have been induced by the experimental infection were not measured. Instead, antibody response was used as marker of infection. It is unclear to what degree the alternative pathway may be relevant to the spread of FeLV infection. We speculate that in most cases cats will overcome the infection for good. In very few cases -when the infected cats undergo immunosuppression due e.g. to concomitant FIV infection -full-blown FeLV infection with bone marrow involvement and viral shedding may develop. It will be important to determine to what extent this may occur.