Granulocyte and monocyte adsorptive apheresis induces apoptosis of neutrophils and release of a novel chemoattractant for desensitization of interleukin-8 response
Objective: Apoptotic cells participate in maintenance of homeostasis of the adaptive immune system. Granulocyte/monocyte adsorptive apheresis (GMA) performed with an Adacolumn has been shown to have clinical efficacy together with immunomodulatory effects for immune-mediated disorder cases, such as inflammatory bowel disease (IBD) or psoriatic arthritis. Although induction of apoptosis in neutrophils by GMA has been observed, the detailed mechanism remains unclear. Methods: To focus on phagocytosis-induced cell death (PICD) that induces apoptotic neutrophils, a comparative study utilizing a GMA-carrier (leukocyte adsorbing carrier for Adacolumn) and yeast particles was performed with in vitro and in vivo examinations. Results: L-selectin was significantly (P = 0.0133) shed, reactive oxygen species (ROS) production was promoted (P = 0.0019), and apoptosis induction was enhanced (P = 0.0087) by peripheral blood co-cultured with the GMA-carrier or yeast particles as compared to incubated blood alone. Furthermore, degranulation of myeloperoxidase, elastase, and lactoferrin was increased by both treatments, while the highest level of interleukin-1 receptor antagonist release was found with GMA-carrier treatment (P = 0.0087) as compared to the yeast particles. Plasma from blood treated with the GMA-carrier showed chemotactic activity, and suppressed neutrophil migration to IL-8 and LTB4. In vivo results demonstrated that neutrophil chemotaxis to IL-8 was desensitized (P = 0.0078) in rabbits following GMA apheresis, while CXCR1 and CXCR2 expressions in neutrophils were reduced by exposing peripheral blood to the GMA-carrier. Conclusions: GMA may regulate the immune system in patients with an immune-mediated disorder by inducing a biological response of neutrophils with a PICD-like reaction.
Adsorptive depletion of α4 integrin(hi)- and CX3CR1(hi)-expressing proinflammatory monocytes in patients with ulcerative colitis
We found high expressions of alpha4 integrin and CX(3)CR1 on monocytes in patients with active UC, known to promote the extravasation of CD14(+)CD16(+) monocytes into the mucosa. GMA effectively depletes CD14(+)CD16(+) monocytes and concomitantly increases CD14(hi)CD16(-)CCR2(low) “immature” monocytes; thus GMA was associated with the emergence of less inflammatory monocyte phenotype in circulation.
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