Assessing the immunomodulatory potential of high-molecular-weight extracts from mushrooms; an assay based on THP-1 macrophages

Food is a potential source of immunomodulating compounds that may be used to steer immune responses towards a desired status such as reducing inflammatory disorders. However, to identify and characterize such bioactive compounds, biologically relevant and standardized assays are required. Macrophages play an important role in immunomodulation and are suited for developing cell-based assays. An assay was developed based on macrophages, in a homogeneous differentiation state, using the human monocytic cell line THP-1 previously used to assess immunomodulatory properties of low-molecular-weight allergens, hormones, dietary supplements and therapeutic drugs.

Zymosan and mushroom polysaccharide extracts lead to a heterogeneous differentiation state of THP-1 monocytes, and these cells secrete low levels of cytokines upon stimulation. Differentiation into macrophages using a low concentration of phorbol 12-myristate 13-acetate improved responsiveness. Elevated levels of cytokines were secreted by cells in a homogenous differentiation state. In addition, it was determined that the assay performs best when using cells at a concentration of (2.5-5) × 10(5) cells mL(-1).

An assay was developed suitable to distinguish the immunomodulatory properties of food compounds in a reproducible manner. It was evaluated using eight mushroom species by measuring the secretion of relevant cytokines TNF-α, IL-1β, IL-6 and IL-10.