[Skin reactions to isolated bacterial cell wall components, bacterial peptidoglycan in particular]

To elucidate the pathogenetic mechanism of bacterial-allergical diseases and of reactions provoked by bacterial test substances (e.g. the intracutaneous test), it is necessary to analyse carefully various factors involved in these reactions. To try to separate toxic from immunological reactions minute amounts of peptidoglycan in four different preparations were applied to humans by intracutaneous injections. Peptidoglycan, an immunologically well defined wall components of almost all bacteria and which is therefore ubiquitous, was isolated from staphylococci and streptococci. The skin reactions were evaluated by macroscopical, microscopical and immunohistological observations, as well as by electromicroscopy and statistical means. Several findings indicate the involvement of immunological factors in the observed skin reactions. In some cases no measurable reaction was seen, whereas in others typical skin reactions occurred. Similar reactions were produced by the antigenically related peptidoglycans isolated from Staphylococcus aureus and Staphylococcus epidermis. These reactions differed, however, from those elicited by peptidoglycan preparations from Streptococcus pyogenes type A. Patients with chronic bacterial infections and who were injected by four bacterial preparations demonstrated a significant increase in delayed hypersensitivity reaction compared with two other groups of patients (atopic patients without chronic infection). Because of the very low test dose, necrotic skin reactions, which occur in animal experiments, were not observed.