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Infection and Immunity, March 2000, p. 1312-1318, Vol. 68, No. 3
Department of Pathobiology, University of
Pennsylvania, Philadelphia, Pennsylvania
19104-6050,1 and Department of
Immunology, The Strathclyde Institute of Biomedical Sciences,
University of Strathclyde, Glasgow, G4 ONR, Scotland2
Received 27 October 1999/Returned for modification 2 December
1999/Accepted 16 December 1999
Since the CD40/CD40 ligand (CD40L) interaction is involved in the
regulation of macrophage production of interleukin 12 (IL-12) and
T-cell production of gamma interferon (IFN-
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
The CD40/CD40 Ligand Interaction Is Required for
Resistance to Toxoplasmic Encephalitis

), effector cell functions associated with resistance to Toxoplasma gondii,
the role of CD40L in immunity to this parasite was assessed. Infection of C57BL/6 mice with T. gondii results in an upregulation
of CD40 expression on accessory cell populations at local sites of
infection as well as in lymphoid tissues. Splenocytes from C57BL/6 mice infected with T. gondii for 5 days produced high levels of
IL-12 and IFN-
when stimulated with toxoplasma lysate antigen, and blocking CD40L did not significantly alter the production of IFN-
or
IL-12 by these cells. Similar results were observed with splenocytes and mononuclear cells isolated from the brains of chronically infected
mice. Interestingly, although CD40L
/
mice infected with
T. gondii produced less IL-12 than wild-type mice, they
produced comparable levels of IFN-
but succumbed to toxoplasmic
encephalitis 4 to 5 weeks after infection. The inability of
CD40L
/
mice to control parasite replication in the
brain correlated with the ability of soluble CD40L, in combination with
IFN-
, to activate macrophages in vitro to control replication of
T. gondii. Together, these results identify an important
role for the CD40/CD40L interaction in resistance to T. gondii. However, this interaction may be more important in the
control of parasite replication in the brain rather than the generation
of protective T-cell responses during toxoplasmosis.
*
Corresponding author. Mailing address: Department of
Pathobiology, University of Pennsylvania, 3800 Spruce St.,
Philadelphia, PA 19104-6050. Phone: (215) 573-7772. Fax: (215)
573-7023. E-mail: chunter{at}phl.vet.upenn.edu.
Present address: Institute for Medical Microbiology and Virology,
Heinrich-Heine-University, 40225 Dusseldorf, Germany.
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