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- NEW YORK (Reuters
Health) - The body's B cells, charged with producing antibodies that fight
infection, carry live AIDS viruses (HIV) on their surfaces and deliver
them throughout the body, scientists have discovered.
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- Besides T cells, which HIV targets for infection, various
other cells in the body serve as reservoirs for the virus. Before now,
though, researchers have not focused on the role of B cells as possible
HIV reservoirs, according to Dr. Susan Moir from the National Institutes
of Health in Bethesda, Maryland, and associates.
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- B immune cells isolated from the blood or from lymph
nodes harbored significant amounts of live HIV, the study authors report,
though there was no evidence that the virus actually reproduced within
the cells.
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- Instead, the virus remained bound to the surface of the
B cell. In contrast, HIV enters T immune cells where it uses the cell's
machinery to produce copies of itself for release outside the T cells,
according to the report in the September issue of The Journal of Experimental
Medicine.
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- HIV appeared to stick to the B cell surface on CD21 molecules
that are normally used as binding sites for the body's infection-fighting
complement molecules, the researchers note. When released from the surface,
the virus is fully able to replicate itself.
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- Recent research has demonstrated that HIV bound to B
cells through immune complexes such as these are far more infectious to
the target T cells than are viruses floating free in the blood, the investigators
explain.
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- B cells might have an even greater opportunity than other
HIV carriers to transmit virus to T cells, because they can circulate through
the blood and migrate into tissues where T cells reside.
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- Moreover, with the constant triggering of CD21 in poorly
controlled HIV infection, B cells can become highly activated and even
more likely to spread the infection to other parts of the body, the authors
suggest.
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- ``Thus, our findings provide new insights regarding the
potential role of B cells as a unique...reservoir for HIV,'' Moir and colleagues
conclude.
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- SOURCE: The Journal of Experimental Medicine 2000;192:637-646
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