Does zinc deficiency impair immune-cell signaling and epithelial barrier repair?

Zinc is required for both adaptive immune activation and epithelial junctional integrity. The claim is supported: evidence is strongest for immune-cell signaling mechanisms and experimental barrier dysfunction, while direct human repair outcomes remain less established.

Immune-cell signaling

• Zinc deficiency impairs T-cell receptor–linked activation, including reduced NF-κB activity and lower IL-2/IL-2-receptor expression; altered MAPK, PKC, and IKK signaling may contribute. These pathways plausibly reduce lymphocyte activation and proliferation.
• In a small randomized nursing-home study of zinc-deficient older adults, 30 mg/day zinc for 3 months increased serum zinc and improved lymphocyte proliferation; changes in zinc correlated with proliferation and T-cell numbers. Results across supplementation studies are heterogeneous and do not yet establish patient-important outcomes.
• This is not evidence for empiric high-dose zinc: immune signaling is concentration-dependent, and excess zinc can suppress T-cell responses.

Epithelial-barrier mechanisms

• In intestinal Caco-2 cells, zinc deprivation reduced transepithelial electrical resistance and increased dextran/mannitol paracellular flux, directly demonstrating a leakier epithelial barrier.
• Depletion disrupts or reduces ZO-1, occludin, β-catenin, E-cadherin, and airway junction-complex proteins. Proposed mechanisms include calpain-mediated occludin degradation and reduced EGR1-dependent claudin-3 transcription.
• Airway epithelial zinc depletion, especially with cigarette-smoke exposure, reduced ZO-1 and claudin-1 and increased ionic and tracer permeability. Under inflammatory or Fas-mediated injury, deficiency accelerated apoptosis, junctional proteolysis, and leak in culture.

Clinical interpretation

• Low plasma zinc during infection, trauma, or chronic inflammation may reflect IL-6/TNF-α–associated metallothionein induction and redistribution into hepatic/cellular compartments rather than depleted stores. Interpret levels with fasting/sampling context, albumin, and CRP and/or AGP; consider reassessment after acute illness.

Bottom line

• Zinc deficiency credibly compromises T-cell signaling and epithelial barrier maintenance/repair biology. For a 71-year-old, confirmation of true deficiency before repletion is important, since inflammatory hypozincemia and excess supplementation can both mislead management.