A non-protective T helper 1 response against the intra-macrophage protozoan Theileria annulata

J D Campbell, D J Brown, A K Nichani, S E Howie, R L Spooner, E J Glass

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

Theileria annulata is a protozoan parasite which infects and transforms bovine macrophages. Infected macrophages possess augmented antigen presentation capabilities, as they are able to activate the majority of T cells from unexposed animals. In vivo, T cells in the draining lymph node (principal site of parasite development) are activated 'non-specifically' by the parasite. This event is followed by failure of the immune response to control the infection. Protective immune responses against intra-macrophage protozoa are usually mediated by T helper 1 (Th1) T cell responses. Here we examine the cytokine responses made by T. annulata-activated T cells. We show that the outcome of in vitro activation of T cells by parasitized macrophages is a skewing of their cytokine responses towards preferential expression of interferon-gamma (IFN-gamma) mRNA. The in vitro response is mirrored during in vivo infection, as greatly elevated amounts of IFN-gamma protein are found in lymph efferent from infected lymph nodes, while expression of IL-4 mRNA within the node stops. IFN-gamma production does not correlate with protection against the parasite, as infected cells flourish during peak IFN-gamma production, and only very small amounts of IFN-gamma are produced during the effective immune response of an immunized animal. Overproduction of IFN-gamma and loss of IL-4 expression are also likely to account for the failure of B cells to reach the light zone of germinal centres, a developmental step which is tightly regulated by cytokines.
Original languageEnglish
Pages (from-to)463-70
Number of pages8
JournalClinical & Experimental Immunology
Volume108
Issue number3
Publication statusPublished - Jun 1997

Keywords / Materials (for Non-textual outputs)

  • Animals
  • Cattle
  • Cells, Cultured
  • Female
  • Interferon-gamma
  • Interleukin-4
  • Macrophages
  • Male
  • Th1 Cells
  • Theileria annulata

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