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Infect. Immun., May 1996, 1609-1613, Vol 64, No. 5
LA Sporn and VJ Marder
Rickettsia rickettsii infection results in numerous responses by cultured
endothelial cells, among them a rapid, transient increase in steady-state
levels of tissue factor mRNA (L.A. Sporn, P.J. Haidaris, R.-J. Shi, Y.
Nemerson, D.J. Silverman, and V.J. Marder, Blood 83:1527- 1534, 1994). In
this study, production of interleukin-1 (IL-1) was measured during
infection and its potential role in autocrine cell stimulation was
investigated. A fivefold increase in levels of IL-1 alpha antigen was
measured in cell lysate samples by enzyme-linked immunosorbent assay at 18
h of infection. The majority of IL-1 alpha remained cell associated, as no
significant increase was detected in culture medium. No IL-1 beta antigen
was detected in cell lysates or culture medium from either control or
infected cultures. A dramatic increase in the levels of IL-1 alpha mRNA
occurred following infection, as measured by reverse transcriptase PCR,
which revealed the appearance of the expected 421-kb product with RNA
extracted from cells infected for 4 h and no detectable product from
control cell samples. The presence of functional, cell-associated IL-1
alpha activity in infected cells was confirmed, following disruption, by
the ability of the infected cells to induce tissue factor expression in
target endothelial cells. Such induction was eliminated by pretreatment of
the disrupted cell samples with neutralizing antibodies against IL-1 alpha
but not against IL-1 beta. To investigate whether endogenously produced
IL-1 participates in the stimulation of tissue factor expression,
neutralizing antibodies against IL-1 or the IL-1 receptor antagonist were
added to culture medium during infection. Both anti-IL-1 alpha and the IL-1
receptor antagonist resulted in approximately 40% inhibition of tissue
factor expression, thus implicating IL-1 alpha in autocrine cell
stimulation.
Copyright © 1996, American Society for Microbiology
Interleukin-1 alpha production during Rickettsia rickettsii infection of cultured endothelial cells: potential role in autocrine cell stimulation
Department of Medicine, University of Rochester School of Medicine & Dentistry, New York, USA.
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