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A review of the British Society for Histocompatibility and Immunogenetics (BSHI) Guideline 'HLA matching and donor selection for haematopoietic progenitor cell transplantation' published in 2016 was undertaken by a BSHI appointed writing committee. Literature searches were performed and the data extracted were presented as recommendations according to the GRADE nomenclature., (© 2021 The Authors. International Journal of Immunogenetics published by John Wiley & Sons Ltd.)

Lipoxins (LXs) are endogenously produced anti-inflammatory agents that modulate leukocyte trafficking and stimulate nonphlogistic macrophage phagocytosis of apoptotic neutrophils, thereby promoting the resolution of inflammation. Previous data suggest a role for altered protein phosphorylation and cytoskeletal rearrangement in LX-stimulated phagocytosis but the exact mechanisms remain unclear. In this study we examine the effects of LXA4 on the protein phosphorylation pattern of THP-1 cells differentiated into a macrophage-like phenotype. THP-1 cells stimulated with LXA4 (1 nM) exhibit dephosphorylation of a 220-kDa protein. Using mass spectrometry, this protein was identified as MYH9, a nonmuscle myosin H chain II isoform A, which is involved in cytoskeleton rearrangement. THP-1 cells treated with LXA4 adopt a polarized morphology with activated Cdc42 localized toward the leading edge and MYH9 localized at the cell posterior. Polarized distribution of Cdc42 is associated with Akt/PKB-mediated Cdc42 activation. Interestingly, the annexin-derived peptide Ac2-26, a recently described agonist for the LXA4 receptor, also stimulates macrophage phagocytosis, MYH9 dephosphorylation, and MYH9 redistribution. In addition, we demonstrate that LXA4 stimulates the phosphorylation of key polarity organization molecules: Akt, protein kinase Czeta, and glycogen synthase kinase-3beta. Inhibition of LXA4-induced Akt and protein kinase Czeta activity with specific inhibitors prevented LXA4-stimulated phagocytosis of both apoptotic polymorphonuclear neutrophils and lymphocytes, highlighting a potential use for LXA4 in the treatment of autoimmune diseases. Furthermore, phosphorylation and subsequent inactivation of glycogen synthase kinase-3beta resulted in an increase in phagocytosis similar to that of LXA4. These data highlight an integrated mechanism whereby LXA4 regulates phagocytosis through facilitative actin cytoskeleton rearrangement and cell polarization.

Background: Phagocytic removal of apoptotic cells is an important regulatory event in development, tissue homoeostasis, and inflammation. There are several methodologic problems with most in vitro studies of the molecular mechanisms of apoptotic cell phagocytosis. First, cell loss occurs during rigorous washing of adherent macrophages required to ensure removal of noningested particles. Second, discrimination of adherent or internalised apoptotic cells is difficult. Third, microscopic quantification is time consuming and has the potential for significant interobserver error. Fourth, subsequent analysis of phagocyte populations is difficult., Methods: We used a flow cytometric method that allows quantification of phagocytosis of fluorescently labelled apoptotic cells with the use of multiparameter flow cytometric analysis., Results: Phagocytosis of apoptotic cells was validated by use of inhibitors (cytochalasins) or low temperature and counterstaining with cell surface markers for the phagocytic targets to exclude binding to the phagocytic surface. Populations of phagocytic macrophages were sorted, and the presence of internalized apoptotic material was validated by microscopy., Conclusions: The technique we used in this study allows observer-independent analysis of phagocytosis of apoptotic cells by macrophages. Importantly, phagocytic or nonphagocytic populations could be subjected to further characterization with the use of flow cytometry with additional fluorochrome reagents and can be re-cultured to study underlying regulatory mechanisms., (Copyright 2002 Wiley-Liss, Inc.)