Microflora-associated defense stimulating factors.

Mucosal surfaces are habitats for the physiological microflora and are closely related to the mucosal immune compartment (mucosa-associated lymphoid tissue, MALT). Recently, considerable evidence has accumulated showing that various members of the physiological microflora liberate low molecular weight substances which, apparently, are essential for the adequate immune response of the host. Antibiotic decontamination (e.g. of the BALB/c mouse gastrointestinal tract) results in a lack of generation of immunopriming microbial substances leading to immunosuppression. Biochemical analysis of the microbial substances revealed reproducible chromatographic fractions which selectively influence maturation, proliferation and activation of mononuclear immune cells.