The primary compounds in medicinal mushrooms that support the immune system are polysaccharides. Polysaccharides, such as Lentinan from shiitake mushrooms, impact how well the body responds to invading pathogens. They do this by augmenting the responsiveness of host cells to lymphocytokines, hormones and other biologically active substances (1).

A study that looked at the impact of shiitake mushroom consumption on immunity found that consuming shiitake mushrooms daily supported immunity by significantly increasing NK-T (natural killer T) and Gamma-Delta T cell proliferation and activation. NK-T cells and Gamma-Delta T cells play a role in the initiation and propagation of the immune response. Shiitake mushrooms were also shown to increase sIgA (secretory immunoglobulin A) levels, which is found in mucous secretions and is the first line of defense against bacteria, parasites and viruses. Additionally, CRP (C-reactive protein) levels were significantly reduced by approximately 30% (2).

Reishi mushrooms contain multiple constituents that may contribute to their nutritional properties such as triterpenes and polysaccharides (3).

Researchers evaluated the immunomodulatory activity of beta-glucans, a polysaccharide derived from reishi mushrooms, on children and found that study participants who were given 350mg β-glucans, had a significantly increased number of circulating immune cells (CD3+, CD4+ and CD8+ T cells) (4). This finding indicates that β-glucans from reishi mushrooms increase the frequency of immune system cells in the peripheral blood. This is important because these cells play a critical role in the defense against infectious threats.

Maitake mushrooms contain D-fraction polysaccharides which have a unique structure from other mushrooms. D-fraction polysaccharides have a higher molecular weight which is believed to contribute to activation of a greater number of immune cells (5).