The role of CD8 T lymphocytes in rickettsial infections

David H. Walker, J. Stephen Dumler

Research output: Contribution to journalReview articlepeer-review

17 Scopus citations


Arthropod-borne obligately intracellular bacteria pose a difficult challenge to the immune system. The genera Rickettsia, Orientia, Ehrlichia, and Anaplasma evolved mechanisms of immune evasion, and each interacts differently with the immune system. The roles of CD8 T cells include protective immunity and immunopathology. In Rickettsia infections, CD8 T cells are protective mediated in part by cytotoxicity toward infected cells. In contrast, TNF-α overproduction by CD8 T cells is pathogenic in lethal ehrlichiosis by induction of apoptosis/necrosis in hepatocytes. Yet, CD8 T cells, along with CD4 T cells and antibodies, also contribute to protective immunity in ehrlichial infections. In granulocytic anaplasmosis, CD8 T cells impact pathogen control modestly but could contribute to immunopathology by virtue of their dysfunction. While preliminary evidence indicates that CD8 T cells are important in protection against Orientia tsutsugamushi, mechanistic studies have been neglected. Valid animal models will enable experiments to elucidate protective and pathologic immune mechanisms. The public health need for vaccines against these agents of human disease, most clearly O. tsutsugamushi, and the veterinary diseases, canine monocytotropic ehrlichiosis (Ehrlichia canis), heartwater (Ehrlichia ruminantium), and bovine anaplasmosis (A. marginale), requires detailed immunity and immunopathology investigations, including the roles of CD8 T lymphocytes.

Original languageEnglish (US)
Pages (from-to)289-299
Number of pages11
JournalSeminars in Immunopathology
Issue number3
StatePublished - May 26 2015


  • Anaplasma
  • CD8 T lymphocytes
  • Cytotoxic lymphocytes
  • Ehrlichia
  • Orientia
  • Rickettsia
  • TNF-α

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology


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