Immunology: Leishmania Susceptibility Puzzle Gets Another Twist

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Science  16 Feb 1996:
Vol. 271, Issue 5251, pp. 912
DOI: 10.1126/science.271.5251.912


A strain of mice called BALB/c can't fight off infection by a parasitic protozoan called Leishmania major. Understanding why the animals fail to mount a cell-mediated immune attack on the parasite might help immunologists understand why human beings also vary in their susceptibility to Leishmania, which is believed to afflict 12 million people worldwide. Researchers have been following a promising lead: The animals appear to make an inappropriate antibody response, mediated by the cytokine interleukin-4 (IL-4). Now two papers in this issue ( pp. 984 and 987) put that idea in doubt. They indicate that IL-4 is not involved at all, but rather that the animals' T cells are unable to respond to another cytokine, interleukin-12, that helps trigger cell-mediated immunity. Still, other immunologists, noting the large amount of contradictory data, are not yet ready to dismiss IL-4 as a cause of the animals' Leishmania susceptibility.