Early Development in Monkeys of Cutaneous Resistance to Reinfection with Rickettsia tsutsugamushi

Discussion and summary

These findings provide evidence that immunity factors were active in the skin in the immunologic defense of rhesus monkeys experimentally infected by the intradermal route with scrub typhus rickettsiae, 6 days after exposure to the rickettsiae and several days before circulating antibodies had reached levels high enough to rid the blood of organisms. In 3 groups of monkeys, development of specific dermal lesions was completely suppressed at sites of the second, third, and fourth injections of scrub typhus rickettsiae when an interval of 6 days separated the first from subsequent injections, while in a single group of monkeys (Group 1) given 3 injections at a 3-day interval, lesions occurred at 2 injection sites. Although the role of circulating antibodies in the state of resistance to superinfection in the skin is unknown, the fact that presence of the immune state in the skin of a single monkey was established at the time this animal was circulating rickettsiae in the blood favors the suggestion that other immunity factors besides circulating antibody were at work in the dermal resistance of monkeys inoculated by the technique employed.