immunology of infectious and parasitic diseases - XXXVII Congress ...

INVOLVEMENT OF TNF RECEPTORS IN APOPTOSIS OF ALVEOLAR
MACROPHAGES AFTER MYCOBACTERIA INFECTION
MICHELE FERNANDES RODRIGUES (1) ; BÁRBARA BRUNA MUNIZ
FIGUEIREDO (1) ; ALICE BELLEIGOLI REZENDE (1) ; CAIO CÉSAR DE SOUZA
ALVES (1) ; ANA PAULA FERREIRA (1) ; HENRIQUE COUTO TEIXEIRA (1) .
1 Laboratório de Imunologia, Departamento de Parasitologia, Microbiologia e
Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Juiz de
Fora, Juiz de Fora, MG, Brasil
Introduction: Apoptosis of macrophages has been reported as an effective
host strategy to control the growth of intracellular pathogens, including
pathogenic mycobacteria. TNF-α plays an important role in the modulation of
apoptosis of infected macrophages. TNF-α exerts its biological activities via two
distinct cell surface receptors, the 55-kDa receptor (TNF-R1) and the 75-kDa
receptor (TNF-R2) whose extracellular domain can be released by proteolysis
forming soluble TNF receptors (sTNFR-1 and sTNFR-2). The signaling through
TNF-R1 initiates the majority of the biological functions of TNF-α, leading to
either cell death or survival whereas TNF-R2 mediates primarily survival
signals. Here, the expression of TNF-a receptors and the apoptosis of alveolar
macrophages were investigated during infection with virulent and avirulent
mycobacteria in mice. Methods and Results: C57BL/6 mice were
intratracheally infected with avirulent (BCG Moreau) and virulent (ATCC19274)
strains of M. bovis. TNFR1 -/- mice were infected by BCG only. Mice were killed
3 and 7 days after infection and lung cells obtained by bronchoalveolar lavage
(BAL). Alveolar macrophages were differentiated according to their
CD11b/CD11c profiles and apoptosis was assessed by flow cytometry using
annexin V-FITC/PI labeling. Cell surface TNFR1 and TNFR2 were studied using
FITC anti-mouse CD120a (TNFR1) and PE anti-mouse CD120b (TNFR2).
Levels of soluble TNF receptors (sTNF-R1 and sTNFR2) in BAL were
measured by ELISA. A significant increase of apoptosis and high expression of
TNFR1 were observed in alveolar macrophages at 3 and 7 days after infection
with M. bovis BCG but only on day 7 in C57Bl/6 mice infected with the virulent
M. bovis. Low surface expression of TNFR1 and increased levels of sTNFR1 on
day 3 after infection by the virulent strain were associated with reduced rates of
apoptotic macrophages. In addition, a significant reduction in apoptosis of