Unlike any other cell type, immune cells traverse blood, lymph, and tissues, and so, they are uniquely exposed to all of the different oxygen levels in the body (physioxia).

Ischemic injury and tumors can produce oxygen levels that are particularly low (hypoxia). None of these in vivo environments compare to room air oxygen, which is where most immunological assays are performed. That is an essential disconnect between in vitro and in vivo Immunology, contributing to problems with Reproducibility and Translatability of findings.

Evidence is accumulating that oxygen and Reactive Oxygen Species (ROS) affect immune cell function in profound ways.

It is possible to control in vitro environments to the proper oxygen level for culturing cells as well as handling cells.