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Infect. Immun., 03 1997, 986-993, Vol 65, No. 3
JN Samsom, A Annema, PH Groeneveld, N van Rooijen, JA Langermans and R van Furth
During a secondary Listeria monocytogenes infection in mice, the bacteria
are eliminated more rapidly from the liver and spleen than during a primary
infection. This acquired resistance against a secondary infection is
dependent on T lymphocytes, which induce enhanced elimination of bacteria
via stimulation of effector cells such as neutrophils, resident
macrophages, exudate macrophages, and hepatocytes. The aim of the present
study was to determine the role of the resident macrophages in acquired
resistance against a secondary L. monocytogenes infection in mice. Mice
which had recovered from a sublethal primary infection with 0.1 50% lethal
dose (LD50) of L. monocytogenes intravenously (i.v.), i.e., immune mice,
received a challenge of 1 LD50 of L. monocytogenes i.v. to induce a
secondary infection. At 2 days prior to challenge, immune mice were given
an i.v. injection of liposomes containing dichloromethylene-diphosphonate
(L- Cl2MDP) to selectively eliminate resident macrophages from the liver
and spleen. Control immune mice received either phosphate-buffered saline
(PBS) or liposomes containing PBS (L-PBS). Treatment of mice with L-Cl2MDP
effectively eliminated resident macrophages from the liver and spleen but
did not affect the number of granulocytes, monocytes, or lymphocytes in
peripheral blood or their migration to a site of inflammation. Phagocytosis
and killing of L. monocytogenes by peritoneal exudate cells elicited with
heat-killed L. monocytogenes were similar in all groups of immune mice. On
day 3 of a secondary infection, the number of L. monocytogenes organisms in
the livers and spleens of L-Cl2MDP-treated immune mice was 4 log10 units
higher than in immune mice treated with PBS or L-PBS. The concentration of
reactive nitrogen intermediates in plasma, a measure of the severity of
infection, was 70-fold higher for L-Cl2MDP-treated immune mice than for
PBS- or L-PBS-treated immune mice. Treatment with L-Cl2MDP significantly
increased the number of inflammatory foci in the liver and spleen,
decreased their size, and affected their structure. From these results, we
conclude that resident macrophages are required for the expression of
acquired resistance against a secondary L. monocytogenes infection in mice.
Copyright © 1997, American Society for Microbiology
Elimination of resident macrophages from the livers and spleens of immune mice impairs acquired resistance against a secondary Listeria monocytogenes infection
Department of Infectious Diseases, University Hospital, Leiden, The Netherlands.
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