Rendered Powerless by Heme

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Science  05 May 2006:
Vol. 312, Issue 5774, pp. 661
DOI: 10.1126/science.312.5774.661b

Malaria represents one of the greatest threats to human health in tropical and subtropical regions. Aside from its direct effects, the Plasmodium parasite causes a general suppression of the immune system.

Millington et al. observed that mice infected with the rodent-specific strain P. chabaudi were less able to produce antibodies to a third-party antigen. Both in culture and in vivo, parasite-infected erythrocytes inhibited the maturation of dendritic cells, as shown by a reduction in the expression of activation markers. Hemozoin (the product of hemoglobin degradation) was found to impede dendritic cell maturation and, in turn, to reduce the ability to activate naïve T cell responses. During an infection with P. chabaudi, these effects on dendritic cells manifest themselves as a reduction in CD4+ T cell proliferation and migration into B cell-rich regions of the lymph node. The subsequent deficit in T cell-assisted B cell expansion thereby offers an explanation for the reduced antibody production seen in infected mice. — SJS

J. Biol. 5, 5 (2006).

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