Cell type-specific autophagy in human leukocytes: signatures of aging, sex, and nutrient restriction.

Macroautophagy (referred to here as autophagy) is thought to play a critical role in aging and age-related disease, making it a priority for development of targeted human therapies. We developed a flow cytometry-based method to measure autophagic flux in 19 subpopulations from whole blood, using chloroquine (CQ) to inhibit lysosomal degradation, and the autophagy protein MAP1LC3B (microtubule associated protein 1 light chain 3 beta) isoform II/LC3B-II to measure autophagic flux (the acquisition and degradation of autophagic cargo over time). Autophagic flux varies by cell type and is higher in whole blood compared with RPMI culture media. Basal autophagic flux shows sex- and age-specific variations. Further, monocytes, but not T cells, respond robustly to amino acid starvation by increasing autophagy, with older individuals exhibiting stronger responses, particularly in non-classical monocytes. These findings underscore the importance of cell type-specific autophagy measurements to understand the effects of aging, sex and nutrition, to develop targeted interventions for age-related diseases.