The important part is:

>Based on our results we propose that immune exhaustion perpetuates long-COVID due to the seemingly complete reduction of IFNγ and IL-8, as well as significant decreases in IL-2, IL-4, IL-6, IL-13, and IL-17. Identifying these and other deficiencies will provide clues towards methods to intervene and possibly restore immune function in the context long-COVID. Although functional assays that test the ability of immune cells from individuals with long-COVID to respond to pathogenic stimuli will be required to support this theory.