Targeting B‑cell‑intrinsic insulin receptor signaling to rejuvenate lymphopoiesis and rescue vaccine responses in aging

Kevin Wolf (MD/PhD)· Mar 25, 2026

Mechanism: Aged B cells with hyperactive Insulin Receptor signaling suppress stromal cell IL-7 production, impairing B cell development and vaccine responses. Readout: Readout: Blocking IR restores IL-7 levels, increases naïve B cells by 80%, and improves vaccine-induced germinal centers and antibody affinity.

Hypothesis

Aged B cells actively suppress bone marrow B lymphopoiesis not only through homeostatic competition but via B‑cell‑intrinsic insulin receptor (IR) signaling that remodels the stromal niche to lower IL‑7 production. Blocking IR specifically in aged B cells will restore IL‑7‑dependent lymphopoiesis, increase naïve B cell output, and rescue germinal center formation and vaccine‑induced affinity maturation in old mice.

Mechanistic Rationale

Aged B cells show heightened IR expression and activity (see 6), leading to increased downstream AKT‑mTOR signaling.
This signaling drives secretion of TGF‑β and IFN‑γ from B cells, which act on bone marrow mesenchymal stromal cells to suppress IL‑7 transcription (known IL‑7 regulators).
Reduced IL‑7 diminishes pro‑B to pre‑B transition, contracting the naïve B cell pool and perpetuating the age‑associated repertoire contraction (1, 2).
The resulting low naïve B cell input limits germinal center seeding, compounding AID deficiency (4, 5).
Thus, IR signaling in aged B cells sits upstream of both the cellular competition defect and the molecular AID/E47 deficit.

Testable Predictions

B‑cell‑specific IR knockout in aged mice (using CD19‑Cre IR^fl/fl) will:
- Increase bone marrow IL‑7 mRNA and protein levels (2).
- Elevate frequencies of hematopoietic stem‑cell‑derived pro‑B and naïve B cells (1).
- Restore AID induction after immunization to levels comparable to young adults (4).
- Produce larger, more organized germinal centers and higher affinity IgG antibodies (7).
Pharmacologic IR inhibition (e.g., using the selective antagonist S961) administered to old mice for 2 weeks prior to vaccination will recapitulate the genetic rescue.
In humans, ex‑vivo culture of aged peripheral B cells with IR antagonist will reduce their secretion of TGF‑β/IFN‑γ and increase IL‑7 production by co‑cultured bone marrow stromal cells.

Falsifiability

If B‑cell‑restricted IR loss or blockade fails to raise IL‑7, naïve B cell numbers, AID induction, or germinal center quality in aged mice, the hypothesis is refuted. Likewise, if IR inhibition does not alter aged B cell cytokine output in vitro, the proposed mechanistic link is unsupported.

Hypothesis

Mechanistic Rationale

Aged B cells show heightened IR expression and activity (see 6), leading to increased downstream AKT‑mTOR signaling.

This signaling drives secretion of TGF‑β and IFN‑γ from B cells, which act on bone marrow mesenchymal stromal cells to suppress IL‑7 transcription (known IL‑7 regulators).

Reduced IL‑7 diminishes pro‑B to pre‑B transition, contracting the naïve B cell pool and perpetuating the age‑associated repertoire contraction (1, 2).

The resulting low naïve B cell input limits germinal center seeding, compounding AID deficiency (4, 5).

Thus, IR signaling in aged B cells sits upstream of both the cellular competition defect and the molecular AID/E47 deficit.

Testable Predictions

B‑cell‑specific IR knockout in aged mice (using CD19‑Cre IR^fl/fl) will:

Increase bone marrow IL‑7 mRNA and protein levels (2).
Elevate frequencies of hematopoietic stem‑cell‑derived pro‑B and naïve B cells (1).
Restore AID induction after immunization to levels comparable to young adults (4).
Produce larger, more organized germinal centers and higher affinity IgG antibodies (7).

Pharmacologic IR inhibition (e.g., using the selective antagonist S961) administered to old mice for 2 weeks prior to vaccination will recapitulate the genetic rescue.

In humans, ex‑vivo culture of aged peripheral B cells with IR antagonist will reduce their secretion of TGF‑β/IFN‑γ and increase IL‑7 production by co‑cultured bone marrow stromal cells.