Cellular Immune Responses in Guinea Pigs Immunized with Cell Walls of Histoplasma capsulatum Prepared by Several Different Procedures

Since guinea pigs immunized with water-washed cell walls of Histoplasma capsulatum developed cellular immune responses detectable with cytoplasmic substances, attempts were made to determine whether cytoplasmic contamination of the walls was responsible for the induction of the immune response. Cell walls were treated by several procedures designed to remove possible contamination, namely, extraction with lipid solvents, incubation with proteolytic enzymes, and washing with sodium dodecyl sulfate, and each of the treated preparations was compared with water-washed walls for its ability to induce cellular responses demonstrable with cytoplasmic substances. For comparison, wall glycoprotein was also used as a test antigen. Immune responses were assessed by gross and histological examinations of skin test sites and by assays for the production of migration inhibition factor. A portion of the material inducing the response detectable with cytoplasmic substances was apparently removed or altered by each of the purifying procedures. The cellular immune responses to wall glycoprotein were also altered, however, indicating that more than the mere removal of cytoplasmic substances had occurred. On the basis of the data collected from each of the cellular assays involving wall glycoprotein as the test antigen, the hypothesis is proposed that sodium dodecyl sulfate altered or removed protein from the wall and thus augmented its ability to induce a more intense immediate-type hypersensitivity, whereas incubation with Pronase altered the walls in such a way as to shift the balance toward a more intense delayed-type hypersensitivity. The latter effect was probably due to the removal of carbohydrate from the wall by glucanase or to mannosidase contaminating the Pronase preparation.