Board Thread:Fourth Databook/@comment-4366149-20141122004623/@comment-4366149-20141124155722

Elveonora wrote: Well, besides kekkei genkai they may get HIV as well. Joking aside, boosts in life force (whatever that is), chakra reserves and so on can also occur from transplants, but those aren't unique to a clan.

Awesome, let's roll. Kekkei genkai are techniques/abilities that are inherited through blood. But not all traits inherited through blood are kekkei genkai. Examples are: strong life force that run in clans/families, basic elemental affinities that run in clans (e.g. Fire and Yin for the Uchiha), etc. It is possible to have a trait that runs in a particular clan, and that is not a kekkei genkai. Now unto the next part of your point.

You should consider Kakuzu that gains abilities that are not kekkei genkai when he incorporates foreign hearts into his body, and these abilities can include any clan-trademark Elemental affinity his victims might have. Of course, it works out like that for him specifically because of the special method he uses to incorporate the foreign hearts. So the method does matter a lot. Kabuto also had his own method as well, of which we have only vague details about. Sasuke's body absorbed a lot of Juugo's cell/tissue but he never gained Juugo's abilities, and that's because the method matters. So depending on the method, the results will vary, and abilities or powerups other than kekkei genkai can be gained when an individual incorporates foreign somatic material into their body: Kakuzu gained elemental affinities and Sasuke regenerated a decimated chest. And of course, kekkei genkai can also be gained likewise. (BTW, I don't remember where Kabuto says anything about incorporating Juugo's cells into his body, but I assumed that you're right and replied accordingly).

Summary. It is possible to have a trait that runs in a particular clan, and that is not a kekkei genkai. In the case of Juugo's clan, they simply have a trait that makes it much easier for them to absorb natural energy. Also, as other instances in the manga demonstrates, it is possible for someone (or in this case Kabuto) to incorporate foreign somatic material into their body and subsequently obtain abilities that are not kekkei genkai. Finally, neither the manga nor the databook directly supports your theory. BTW, keep in mind that I'm not claiming that Juugo absolutely doesn't have a kekkei genkai, instead I'm trying to show you why it is impossible to argue that he definitely has a kekkei genkai.