At low concentrations (10–80 μg/mL), HA increased TNF-α production in LPS-stimulated cells of the human myeloid leukemia promonocyte line U937 by threefold (pro-inflammatory activity), whereas at higher concentrations (>100 μg/mL), HA reduced TNF-α production by 10-fold (anti-inflammatory activity) without inducing cytotoxicity. Here, TNF is linked to myeloid leukemia.