Interaction of Actinomyces Organisms with Cationic Polypeptides I. Histochemical Studies of Infected Human and Animal Tissues

Abstract

Histochemical techniques were used to study the nature of acidophilic hyaline clubs arranged radially at the peripheries of Actinomyces colonies in infected lung tissues of two persons. Concentrations of arginine-rich polypeptides were demonstrated in the acidophilic areas and in the cytoplasm of granulocytic leukocytes surrounding the colonies. Exposure of Actinomyces organisms to strongly cationic polypeptides (protamine, histone) in vitro killed the organisms and caused them to develop acidophilic staining. Weakly cationic proteins, ribonuclease, and hemoglobin produced no such effects. No acidophilic component could be detected in fresh broth-grown organisms themselves. Viable and nonviable colonies of the test strain lacking hyaline clubs were injected beneath the skin of guinea pigs. Agrinine-rich cationic polypeptides were evident in the cytoplasm of surrounding leukocytes and permeating the microbial colonies. In light of current evidence pertaining to leukocyte lysosomes and capsule production by Actinomyces and related organisms, the acidophilic hyaline clubs observed in human tissues appear to be a combination of a capsular component of the actinomycete and a cationic polypeptide component of host leukocytes. Organisms deeper in the human tissue colonies retained their normal basophilic reaction, suggesting a protective role for the peripheral hyaline club matrix. The acidophilic club complexes serve to indicate the reaction of cationic polypeptides in response of the human host to infecting Actinomyces organisms. These observations also support a broader concept that antimicrobial polypeptides of leukocyte lysosomes are an important factor in response of both the human and animal host to infecting bacteria.