Well, if it's not too different from the feature in the NH-17...
You've got a passive resistance, and an actual active effort put into purging the toxins. I'm unsure of how much the NH-33 active version would depend on the kidneys since Nashoba was the one whom submitted that article - the nekovakyrja's kidney functions always seemed more tied to regenerating lost blood in general. I'd wager the kidney-filtering is part of that resistance.
Awhile ago, one of Wes' characters - Sakai Yuuko - got stung by a mishhuvurthyar and had to bear up with the paralitic toxin involved, which is quite effective at taking nekos down despite their resistances and immunities. Yuuko chose to forcefully expel the contaminated blood out of her skin (it was described as her exuding red mist from her skin) and though she was a bit woozy from the blood loss, she managed to carry on.