A comparatively small number of misfolded proteins form solid aggregates in tissue due to the change in chemical properties caused by this misfolding, and the result is called an amyloid, and a consequent medical condition is called an amyloidosis. The best known type of amyloid is that associated with Alzheimer's disease, but for many of the others it isn't as clear as how these aggregates cause damage. Nonetheless amyloids all accumulate with age, and thus should be removed by any comprehensive suite of rejuvenation treatments.
One of the other amyloids clearly linked to harm is misfolded transthyretin (TTR), which is implicated as the cause of death in most people who make it to very advanced ages. In the very elderly this form of amyloid clogs the cardiovascular system. There is also an inherited variant of TTR amyloidosis that occurs rarely in younger people due to an unfortunate genetic mutation, and as is often the case in these matters most past research has focused there.
Here is a pointer to a recent paper that results from SENS Research Foundation funded work on one possible way to safely break down transthyretin amyloid, removing its contribution to age-related mortality through the use of catalytic antibodies, thought to be a type of functional component in the innate immune system. If selective antibodies effective at breaking down this form of amyloid are established by searching through the many different types present in humans, then these few proteins can be manufactured in bulk and used as the basis for a treatment:
Peptide bond-hydrolyzing catalytic antibodies (catabodies) could degrade toxic proteins, but acquired immunity principles have not provided evidence for beneficial catabodies. Transthyretin (TTR) forms misfolded β-sheet aggregates responsible for age-associated amyloidosis. We describe nucleophilic catabodies from healthy humans without amyloidosis that degraded misfolded TTR (misTTR) without reactivity to the [correctly folded] TTR (phyTTR).
IgM class B cell receptors specifically recognized the electrophilic analog of misTTR but not phyTTR. IgM but not IgG class antibodies hydrolyzed the particulate and soluble misTTR species. No misTTR-IgM binding was detected. The IgMs accounted for essentially all of the misTTR hydrolytic activity of unfractionated human serum. The IgMs did not degrade non-amyloidogenic, non-superantigenic proteins.
The studies reveal a novel antibody property, the innate ability of IgMs to selectively degrade and dissolve toxic misTTR species as a first line immune function. Catalytic IgMs may clear misfolded TTR and delay amyloidosis [and] the innate antibody repertoire is a source of selective catabodies to toxic proteins.