Specific immunity in mice to heartwater

.~ether t.his is ~lated to the persistence of the orgamsms m the tissues ts not known, but Du Plessis (1982) was able to recover the organism from the liver, spleen and mxocardium of mice 365 days after infection. The myocardium and the lung appeared to have the highest infectivity whereas peritoneal macrophages were ~nly infective for up to 30 days following pnmary infec­ tions. In immune mice, infective material could not be demonstrated in peritoneal macrophages following re­ infection which demonstrates the fact that at least the Kiimm strain does not replicate in peritoneal macro­ phages of re-infected immune mice but does replicate for a short time in macrophages of susceptible mice. Im­ mune sheep serum has no effect on the mfection whether given 6 h prior to infection, or repeated 4 days later (Du Plessis, 1982). . Me Hardy & MacKenzie (1981) showed that Balb/C rruce were more susceptible to the K wanyanga strain of heartwater than either Balb/B or Balb/K mice. That these strains of mice differ only at the H2 locus, provides evi­ dence that the H2 locus is associated with susceptibility to heartwater. . The protective immune response which develops in rruce .appears to. be primarily cell-mediated in nature . Du Plessis (1982) mfected mice with the Kiimm strain by blocking the infection with gloxazone (Dithiosemicarbe­ zone) 8 days after infection to prevent mortality and then ~-challenged 14 days later to ensure they were fully tmmune. Three days prior to the harvesting of therr spleens they were treated with gloxazone (60 p.g/g) in order to sterilize any persistent mfection. Tissue homo­ ~enates were prepared from immune mice and inoculated mto. ~usceptib!e mi~e to show that the gloxazone had stenhzed the mfection. Spleen sus~nsions were made and macropha~es removed by allowmg them to attach to ~lass for 30 rrun. The non-attached cells were inoculated mtraperitoneally into susceptible mice so that 4 x 10 7 cells were inoculated into each mouse. When challenged 30 and 60 days later, the mice were immune to chal­ lenge, whereas mice treated in a similar manner with non-immune lymphocytes were fully susceptible.