Idiopathic neutropenia of childhood is associated with Fas/FasL expression

CD8+HLA-DR+ T cells are increased in patients with severe aplastic anemia

The aim of the present study was to investigate the number and function of CD8+HLA-DR+ cells, which are considered to be activated cytotoxic T lymphocytes (CTLs), in peripheral blood to further examine the pathogenesis of severe aplastic anemia (SAA). Thirty-eight patients with SAA were included in the present study. Patients were screened for paroxysmal nocturnal hemoglobinuria by flow cytometry using anti-CD55 and anti-CD59 antibodies. The number of CD8+HLA-DR+ T cells was measured by three-color flow cytometry using anti-CD8-peridinin chlorophyll, anti-CD3-fluorescein isothiocyanate (FITC) and anti-HLA-DR-FITC antibodies. The expression of perforin, granzyme B, tumor necrosis factor-β (TNF-β) and FasL in CD8+HLA-DR+ T cells was detected by flow cytometry with the appropriate monoclonal antibodies. Total RNA was prepared from purified CD8+HLA-DR+ cells of healthy controls and SAA patients, and then polymerase chain reaction (PCR) was performed. Apoptosis of CD8+HLA-DR+ cells was detected by flow cytometry following staining with Annexin V. The proportion of CD8+HLA-DR+ T cells was analyzed by flow cytometry in peripheral blood and was identified to be significantly higher in untreated SAA than in remission patients and in the controls. The expression of perforin, granzyme B, TNF-β and FasL in CD8+HLA-DR+ T cells was analyzed by flow cytometry and PCR, which revealed increased expression in the untreated SAA group compared with that in the control group. Furthermore, the apoptosis of CD3- bone marrow cells from normal individuals was enhanced following co-culture with CD8+HLA-DR+ T cells from untreated SAA patients. In conclusion, the present study demonstrated that CD8+HLA-DR+ T cells may contribute to bone marrow failure in SAA.

Regulation of human neutrophil apoptosis and lifespan in health and disease

Neutrophils (also called polymorphonuclear leukocytes, PMNs) are the most abundant white blood cells in humans and play a central role in innate host defense. Another distinguishing feature of PMNs is their short lifespan. Specifically, these cells survive for less than 24 hours in the bloodstream and are inherently pre-programed to die by constitutive apoptosis. Recent data indicate that this process is regulated by intracellular signaling and changes in gene expression that define an “apoptosis differentiation program.” Infection typically accelerates neutrophil turnover, and as such, phagocytosis-induced cell death (PICD) and subsequent clearance of the corpses by macrophages are essential for control of infection and resolution of the inflammatory response. Herein we reprise recent advances in our understanding of the molecular mechanisms of neutrophil apoptosis with a focus on regulatory factors and pathway intermediates that are specific to this cell type. In addition, we summarize mechanisms whereby perturbation of PMN death contributes directly to the pathogenesis of many infectious and inflammatory disease states.

New insights into the mechanisms controlling neutrophil survival

PURPOSE OF REVIEW

Neutrophil survival is regulated by a complex convergence of different pathways. The present review analyzes these pathways and discusses how neutrophil survival is modulated during the course of inflammatory reactions.

RECENT FINDINGS

Although apoptosis appears to be the predominant cell death pathway in the neutrophil, recent data reveal that neutrophil survival is also regulated by a number of nonconventional pathways including NETosis, autophagic cell death, and other less characterized mechanisms. This supports an even more complex picture of the mechanisms involved in the regulation of neutrophil survival than previously thought.

SUMMARY

The control of neutrophil survival is central to homoeostasis and resolution of inflammation. Cell death is usually discussed dichotomously in terms of apoptosis or necrosis. There are two main pathways responsible for the stimulation of apoptosis; a death receptor pathway triggered by Fas, tumor necrosis factor alpha, and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and a mitochondrial pathway stimulated by a number of stressors such as DNA damage, growth factor deprivation, and chemotherapy drugs. Nonconventional pathways of neutrophil death include NETosis and autophagic cell death as well as a number of poorly characterized mechanisms. Understanding the integrated pathways responsible for the control of neutrophil survival holds therapeutic promise in infectious and inflammatory diseases.