Il6 Conditional Knockout mouse models

Il6, the mouse ortholog of human IL6, encodes a four-helix bundle cytokine that first binds the nonsignaling Il6ra alpha chain and then recruits two Il6st gp130 molecules to assemble a hexameric complex that activates Jak1 and phosphorylates Stat3, driving Socs3 feedback, hepatic acute phase gene induction, Th17 differentiation with Tgfb, and plasma cell survival. A defining feature is trans-signaling, in which ADAM17-shed soluble Il6ra confers responsiveness on gp130-positive cells lacking the alpha chain, a distinction that shapes allele design: a straight null collapses both arms, an Il6ra conditional or a gp130 chimeric decoy isolates trans-signaling, and humanized IL6 or IL6R knockins are the only credible platform for testing tocilizumab, sarilumab, or siltuximab in vivo. Nulls are viable with blunted acute phase and impaired infection responses, and because Il11, Lif, and Osm also converge on gp130, cytokine-level redundancy should be anticipated when interpreting modest phenotypes.

A floxed Il6 allele paired with Cre gives spatial control that whole body knockouts cannot offer. People use it to separate developmental roles from adult homeostasis, to model somatic mutations, and to match disease that begins in one organ.