Anti-IL-8 autoantibody:IL-8 immune complexes suppress spontaneous apoptosis of neutrophils.
Our previous studies demonstrated that a significant fraction of interleukin-8 (IL-8) in lung fluids from patients with acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS) is associated with anti-IL-8 autoantibodies (anti-IL-8:IL-8 immune complexes). Neutrophils have been implicated in the pathogenesis of ALI/ARDS, and moreover, it is well-established that apoptosis of neutrophils is delayed in patients with ALI/ARDS. The aim of this study was, therefore, to examine the role of anti-IL-8:IL-8 immune complexes in modulating spontaneous apoptosis of normal human neutrophils. Apoptosis was assessed by evaluating morphological changes, measuring enzymatic activity of caspase-3, and determining the extent of DNA degradation. We found that samples containing anti-IL-8:IL-8 immune complexes but not samples from which these complexes were removed inhibited neutrophil apoptosis. Furthermore, the former samples or effectively anti-IL-8:IL-8 complexes induced an increase in the level of antiapoptotic protein, Bcl-X(L). In contrast, levels of proapoptotic proteins Bax and Bak were decreased in the same conditions. Activity of both caspase-3 and caspase-9 was also suppressed by anti-IL-8:IL-8 complex-containing samples. Finally, we established that IgG receptor, FcgammaRIIa, mediates antiapoptotic activity of anti-IL-8:IL-8 complexes and that the key components of the FcgammaRIIa signaling pathway, Src, Syk, PI3 kinase, and ERK, may be involved in regulation of neutrophil apoptosis by the complexes. These studies demonstrate for the first time that anti-IL-8:IL-8 immune complexes have the ability to prolong neutrophil life.
Fudala
Rafal
R
Department of Biochemistry, University of Texas Health Center, Tyler, TX 75708-3154, USA.
Krupa
Agnieszka
A
Matthay
Michael A
MA
Allen
Timothy C
TC
Kurdowska
Anna K
AK
D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology; D000936:Antigen-Antibody Complex / Q000276:immunology; D015703:Antigens, CD / Q000378:metabolism; D017209:Apoptosis / Q000276:immunology*; D001323:Autoantibodies / Q000276:immunology* / Q000494:pharmacology; D053148:Caspase 3 / Q000378:metabolism; D002478:Cells, Cultured; D015536:Down-Regulation / Q000276:immunology; D006801:Humans; D016209:Interleukin-8 / Q000276:immunology*; D009504:Neutrophils / Q000166:cytology* / Q000276:immunology* / Q000378:metabolism; D011014:Pneumonia / Q000276:immunology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011654:Pulmonary Edema / Q000276:immunology; D017452:Receptors, IgG / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology
D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D015703:Antigens, CD; D001323:Autoantibodies; C080568:Fc gamma receptor IIA; D016209:Interleukin-8; D019253:Proto-Oncogene Proteins c-bcl-2; D017452:Receptors, IgG; D053148:Caspase 3