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Infection and Immunity, November 2000, p. 6127-6132, Vol. 68, No. 11
Department of Immunology, Royal Free and
University College London Medical School, Windeyer Institute of
Medical Science, London W1P 6DB,1 and
Department of Infectious Diseases, London School of Hygiene
and Tropical Medicine, London WC1E 7HT,2 United
Kingdom
Received 8 May 2000/Returned for modification 16 July 2000/Accepted 1 August 2000
The early role of natural killer cells and gamma delta T cells in
the development of protective immunity to the blood stage of nonlethal
Plasmodium yoelii infection was studied. Splenic cytokine
levels were measured 24 h after infection of natural killer
cell-depleted immunodeficient and littermate mice or transiently T-cell-depleted normal mice. Splenic gamma interferon levels were significantly increased above background in immunodeficient and littermate mice 24 h after infection. Depletion of natural killer cells resulted in markedly depressed gamma interferon levels and poor
control of parasitemia, particularly in severe combined immunodeficient mice. In the littermates, gamma interferon levels were partially reduced, but parasitemias were resolved normally. However, in athymic
mice, natural killer cell depletion had no effect on gamma interferon
production. Levels of tumor necrosis factor alpha were increased in all
animals 24 h after infection, and responses were not affected by
natural killer cell depletion. However, in T-cell-depleted animals,
both gamma interferon and tumor necrosis factor alpha levels were
decreased 24 h after infection, and depleted mice were unable to
control their parasitemia. These results suggest that the early
production of both cytokines is important in the early control of
parasitemia and that both natural killer and gamma delta T cells
contribute equally towards their production. The data also suggest that
the subsequent resolution of infection requires early production of
gamma interferon, which might act by switching on the appropriate
T-helper-cell subsets and other essential parasitotoxic effector mechanisms.
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Copyright © 2000, American Society for Microbiology. All rights reserved.
Early Nonspecific Immune Responses and Immunity to Blood-Stage
Nonlethal Plasmodium yoelii Malaria

*
Corresponding author. Mailing address: Department of
Immunology, Royal Free and University College London Medical School, Windeyer Institute of Medical Science, 46 Cleveland St., London W1P
6DB, United Kingdom. Phone: 44-020 7679 9354. Fax: 44-020 7679 9357. E-mail: J.deSouza{at}ucl.ac.uk.
Present address: RPRC, University of Washington, Seattle, WA 98121.
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