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cofactor · 1
Antibodies, complement proteins and immune cells are all built from protein, and older adults need more protein than younger ones: PROT-AGE advises 1.0–1.2 g per kilogram of body weight a day for healthy people over 65, together with exercise so the body can use it. Falling short costs twice: muscle is lost and the immune system runs short of raw material.
depletes · 1
Inflammation and muscle loss may form a vicious circle: rising inflammation speeds up muscle breakdown; with less muscle, activity drops, abdominal fat increases, and inflammation climbs again. This is one reason keeping muscle matters so much for health in old age.
regulates · 5
Inflammaging is the chronic low-grade inflammation that comes with age: the same pathway running from NF-κB to interleukin 6 (IL-6) to C-reactive protein (CRP), slowly turned up over the years.
The chronic low-grade inflammation of an aging immune system is linked with cognitive decline and is thought to be one of its drivers. It is not the only cause, and it is intertwined with vascular and metabolic factors.
Chronic stress is linked with immune dysregulation and may speed up immune aging: cortisol that stays high suppresses cell-mediated immunity while pushing low-grade inflammation up. So here, managing stress is not just soft advice; it acts on the same machinery.
The interleukin 6 (IL-6) released by contracting muscle is not the same signal as the IL-6 that visceral fat releases chronically: the contraction kind suppresses tumor necrosis factor (TNF-alpha) and raises anti-inflammatory factors such as IL-10. That is how regular exercise pushes down the baseline of inflammaging while preserving muscle.
Mechanism · One IL-6, two signals
The IL-6 released by contracting muscle is not the same signal as the IL-6 that lingers in visceral fat. The contraction kind suppresses TNF-alpha and raises IL-10 and the IL-1 receptor antagonist, so its effect is anti-inflammatory. Pedersen and Febbraio 2008 describe muscle as an endocrine organ. Regular exercise pushes down the baseline of inflammaging while preserving muscle, breaking the cycle in which inflammation and muscle loss worsen each other.
Evidence · What this review establishes
What this review establishes is the identity of the signal: IL-6 from contracting muscle differs from IL-6 from fat. It gives no prescription for minutes of exercise per week and no timetable for inflammatory markers after a session. What you can take away is the direction: muscle contraction itself sends an anti-inflammatory signal; only regular exercise over time shifts the baseline, and one hard workout is not a medicine.
Background · What exercise cannot replace
Exercise does not replace vaccines and is not an anti-inflammatory drug; vaccination in older adults still follows the schedule for their age. This is only about the path through muscle-derived signals. Keeping muscle also takes enough protein. And a rise in IL-6 from one bout of exercise should not be read as reversing the shrinking of the thymus.
Keep two things apart: filling a gap back to normal is worthwhile, and people who were deficient may get slightly fewer respiratory infections once corrected; topping up someone who already has enough adds nothing. Immunity is not better the higher it goes; a supplement can bring you back to normal, not push you beyond it.