This is the mechanistic claim that underwrites the longevity promise. It rests on Bogomolets’s framing of the reticular connective tissue as the ‘cement’ of the body and on the wider mid-century interest in low-dose immunological stimulation. The mechanism is classified as untested at its mechanism level: no cited study in this bundle directly measured whether ACS selectively strengthens human reticular connective tissue or slows its age-related decline. The late-1940s Western clinical evaluation in 3,500 patients (reported by Joe Schwarcz, McGill OSS, 20 September 2024) concluded that the serum ‘is not a cure for anything’ across the disease indications it was tested for, which is an absence of clinical efficacy rather than a direct mechanistic refutation. The mechanism remains scientifically implausible by modern immunology and is left without empirical support, but a formal mechanistic refutation is not on record in the sources used here.