Oral administration of a fruiting body extract of Boletopsis leucomelas enhances intestinal IgA production in LPS-challenged mice

The present study showed that a hot water extract of the fruiting body of the edible mushroom Boletopsis leucomelas, known as ‘Kurokawa’ Japanese, strongly stimulated IgA-production in mouse spleen cells in our screening experiment. The in vivo study was also conducted with the objective of enhancing adaptive immune response by oral administration of the hot water extract of B. leucomelas (BLE) in lipopolysaccharide (LPS)-challenged mice. The mice were fed a standard diet with or without 0.16% BLE. The mice were also orally administered sodium phosphate buffer or LPS weekly at days 7, 14 and 21. Results indicated that LPS-specific serum IgG, IgM and IgA were increased in the BLE diet group compared to the standard diet group. Interestingly, intestinal total IgA and LPS-specific IgA were significantly increased in the BLE diet group. Moreover, the <1000 Da, 5000–10,000 Da phenol sulphate-positive molecules from BLE showed significant IgA-producing activity.