TNF and COVID-19: To determine the response of immune cells to plasma exosomes, we first treated PBMC isolated from healthy donors with exosomes isolated from the plasma of COVID-19 patients, exosomes isolated from non-COVID plasma, and lipopolysaccharides (LPS) for 16 h, followed by flow cytometry to determine the abundance of intracellular IL-6, IL-8, and TNF-α in PBMC gated for CD3+ lymphocytes.