Specific unresponsiveness to Corynebacterium parvum as measured by delayed hypersensitivity

In order to induce specific unresponsiveness to C. parvum mice were given seven daily i.v./i.p. injections of a high dose of the vaccine, or were given a single dose i.v. injection of C. parvum followed by an i.p. injection of cyclophosphamide (CY). Mice given the high-dose procedure had a significant level of residual footpad reactivity to C. parvum challenge, but subsequent sensitizing injections did not stimulate delayed hypersensitivity (DH). In contrast, mice given C. parvum and CY did not respond to challenge, and they could not be sensitized to C. parvum. Their unresponsiveness was antigenically specific and was stable for at least six weeks. Antibodies to C. parvum were induced by both pretreatment procedures. This is the first report of the production of mice specifically unable to mount DH to a bacterial immune stimulant.