Mechanisms of allergen- and LPS-induced bone marrow eosinophil mobilization and eosinophil accumulation into the pleural cavity: a role for CD11b/CD18 complex.
OBJECTIVE
The mechanisms involved in bone marrow eosinophil emigration and recruitment to inflammatory sites are not fully understood. The involvement of CD11b/CD18 in marrow eosinophil release induced by lipopolysaccharide (LPS) or allergen was investigated in mice.


METHODS
Eosinophil and neutrophil counts in the pleural cavity, blood and bone marrow were performed at different time intervals after the intrathoracic injection of LPS (250 ng/cavity) or ovalbumin (OVA, 12 microg/cavity; into actively sensitized mice) and compared to anti-CD11b/CD 18 (5C6, 1 mg/mouse) or anti-IL-5 (TRFK-5, 500 microg/kg) treated mice.


RESULTS
LPS induced local eosinophil influx, that peaked within 24 h and that was preceded by a decrease in marrow eosinophils at 4 h. Antigenic challenge induced a decrease in marrow eosinophils within 4 h, followed by a long lasting pleural eosinophil accumulation and a persistent increase in marrow eosinophil numbers. Pretreatment with anti-CD11b/CD18 abolished LPS-induced neutrophil and eosinophil accumulation in the pleural cavity at 4 and 24 h, respectively. This pretreatment failed to modify neutrophil emigration from bone marrow, but significantly inhibited marrow eosinophil release at 4 h post-LPS or OVA challenge. Anti-IL-5 pretreatment failed to inhibit LPS-induced pleural eosinophil accumulation and mobilization from bone marrow, but it abolished allergen-induced effects, indicating a role for IL-5 in marrow eosinophil mobilization induced by antigen, but not by LPS challenge.


CONCLUSIONS
Our results suggest that eosinophil migration induced by antigen or LPS into the pleural cavity is preceded by bone marrow eosinophil release through a mechanism that depends on CD11b/CD18.
Larangeira
A P
AP
Departamento de Fisiologia e Farmacodinâmica, IOC, Fundação Oswaldo Cruz, Rio de Janeiro, RJ, Brazil.
Silva
A R
AR
Gomes
R N
RN
Penido
C
C
Henriques
M G
MG
Castro-Faria-Neto
H C
HC
Bozza
P T
PT
D000485:Allergens / Q000276:immunology*; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D001854:Bone Marrow Cells / Q000502:physiology*; D018821:CD18 Antigens / Q000502:physiology*; D002465:Cell Movement / Q000187:drug effects; D004804:Eosinophils / Q000187:drug effects* / Q000502:physiology; D015848:Interleukin-5 / Q000502:physiology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D016177:Macrophage-1 Antigen / Q000502:physiology*; D008297:Male; D051379:Mice; D009504:Neutrophils / Q000187:drug effects / Q000502:physiology; D010994:Pleura / Q000166:cytology*
D000485:Allergens; D000911:Antibodies, Monoclonal; D018821:CD18 Antigens; D015848:Interleukin-5; D008070:Lipopolysaccharides; D016177:Macrophage-1 Antigen