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Infect Immun, June 1998, p. 2698-2704, Vol. 66, No. 6
Microbiology and Tumour Biology Centre,
Karolinska Institutet and Swedish Institute for Infectious Disease
Control, Stockholm, Sweden1;
McGill
Centre for the Study of Host Resistance, McGill University, Montreal
General Hospital, Montreal, Quebec, Canada2; and
Institute of Pathobiology, Addis Ababa University, Addis Ababa,
Ethiopia3
Received 3 September 1997/Returned for modification 13 November
1997/Accepted 12 February 1998
The role of natural versus acquired immunity to Leishmania
aethiopica infection in humans is the focus of our studies. We found in previous studies that mononuclear cells from nonexposed healthy Swedish donors responded to Leishmania antigen
stimulation by proliferation and gamma interferon production. The main
cell type responding was CD3
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Indications of the Protective Role of Natural Killer Cells in
Human Cutaneous Leishmaniasis in an Area of Endemicity
CD16/56+ natural
killer (NK) cells. These findings led us to suggest that the potential
to produce a rapid, nonacquired NK cell response may be a protective
phenotype. In order to test this hypothesis, an area in Ethiopia where
Leishmania is endemic was selected, and peripheral blood
mononuclear cells were obtained from individuals who had lived in the
area most of their lives but had no evidence of past or present
leishmaniasis. Their responses were compared with those of confirmed
leishmaniasis patients from the same region with active lesions or
cured leishmaniasis lesions. Cells from these donors were stimulated in
vitro with L. aethiopica antigen. Responses were measured
by proliferation, cytokine production, and phenotype analysis by
fluorescence-activated cell sorting. The association of
NRAMP1 alleles with the studied phenotype and susceptibility to L. aethiopica-induced leishmaniasis was
also evaluated. The results show that Leishmania antigens
can induce NK cell and CD8+-T-cell responses in vitro. This
is clearly seen in proliferating cells from the cured (immune)
individuals and the apparently protected controls from the area of
endemicity. It contrasted with the reactivity of the patients, where
some NK proliferation was coupled with enhanced CD4+-T-cell
proliferation. We conclude from these observations that NK cells and
CD8+ cells proliferating in response to
Leishmania stimulation are involved in protection from and
healing of (Ethiopian) cutaneous leishmaniasis; however, such
mechanisms appear to be unrelated to the NRAMP1 host
resistance gene.
*
Corresponding author. Mailing address: Microbiology and
Tumour Biology Centre, Karolinska Institutet, Box 280, 17177 Stockholm, Sweden. Phone: 46 8 728 7236. Fax: 46 8 33 15 47. E-mail:
Hannah.Akuffo{at}mtc.ki.se.
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