Mobilisation of mesenchymal infection defence.

Background . Most infections are arrested in epithelial and superficial connective tissues long before antibodies and antigen specific killer cells have been induced; i.e. before the specific defence system has had time enough to come to the rescue. Microbial substances that activate and modulate this non-specific first-line defence in and near the body surfaces may enhance disease resistance, mainly by stimulating the production of anti-microbial substances by epithelia and by local activation of tissue macrophages.

Material and methods . There are many different microbial substances that can activate macrophages. Beta-1,3-glucans from yeast and mushrooms are the most obvious candidates for pharmaceutical development because their chemical composition and mode of action has been clarified in great detail.

Results. Beta-1,3-glucans in purified form provide efficient protection of animals against infections by virus, bacteria, fungi and parasites. Such enhanced protection is obtained after injection as well as after oral or mucosal administration. Beta-1,3-glucans also counteract the toxic effects of bacterial endotoxins and enhance the body’s capacity to destroy cancer cells.

Interpretation. Activation of non-specific immunity in epithelia and in connective tissues by purified microbial substances corresponds to early events in a natural infection process and renders animals more resistant to infections. This way to enhance resistance to microbial infections has been applied with success in animal husbandry with beta-1,3-glucans administrated orally or onto mucosal surfaces. Corresponding use in human medicine is a realistic possibility, in addition to the use of microbial immune modulators as adjuvants in mucosal vaccines.