Functional Maturation during Bovine Granulopoiesis

Abstract

Granulocytic precursor cells undergo morphologic changes in the nucleus and the cytoplasm during the process of granulopoiesis, which takes place in the bone marrow. These changes are associated with the development of stage-specific proteins necessary for the highly specialized roles of polymorphonuclear leukocytes in phagocytosis, bacterial killing, and in mediating the inflammatory process. The objective of the current study was to sequence the various events that occur upon functional development of granulocytic bone marrow cells in the bovine species.Cells were obtained from the bone marrow of clinically healthy cows and separated into different stages of maturation using density gradient centrifugation. Three cellular fractions were obtained that were enriched for either early immature, late immature or mature granulocytic cells. Functions and receptor expressions assessed in the three maturation stages were: FcIgG 2 receptor and CD11b expression, phagocytosis of Escherichia coli, respiratory burst activity, and cellular myeloperoxidase activity. Immature cells expressed already Fc-IgG 2 receptor and CD11b on their cytoplasma membrane. Phagocytic ability was acquired in the myelocytic stage, but only the more mature forms were readily capable of phagocytosis. Promyelocytes, myelocytes and metamyelocytes showed no respiratory burst activity. Only band and segmented cells produced reactive oxygen species. Myeloperoxidase was present at all stages of maturity. Thus, each of the maturation stages was characterized by a selective expression of one or more functions and receptors. Therefore, sequential biochemical maturation is postulated during bovine granulopoiesis. 2859side scatter, F = fluorescence, MFI = mean fluorescence intensity, MPO = myeloperoxidase, PI = propidium iodide, PMA = phorbol 12-myristate 13-acetate, PMN = polymorphonuclear leukocytes, ROS = reactive oxygen species.

Severity of E. coli mastitis is mainly determined by cow factors

“…The limited chemotactic and phagocytic ability in immature cells could be due to membrane rigidity with poor cellular deformability, in association with a large nucleus [141]. The incapacity to produce ROS was attributed to the absence of membrane-bound NADPH-oxidase activity, as myeloperoxidase was already present in the rare azurophilic granules at the promyelocytic stage [239]. These findings were in general agreement with previous observations of Silva et al [212].…”

“…In a subsequent study, the functional maturation sequence during bovine granulopoiesis was established and proposed to be the following: myeloperoxidase activity -Fc-IgG2 receptor expression -CD11b expression -L-selectin -phagocytosisrespiratory burst activity (Fig. 3) [239]. In analogy to human hematopoiesis [83], the acquisition of various biochemical and functional properties in bovine PMN was found to take place in different stages of maturation in the bone marrow.…”

Mathematical Model of the Acute Inflammatory Response to Escherichia coli in Intramammary Challenge

“…However, during the acute inflammatory phase, somatic cells are composed mainly of PMN (Saad and Ostensson, 1990) and most of the blood leukocytes migrating to the inflamed udder are PMN. Second, all rates were considered to be constant at all stages of the inflammatory response even though PMN may enter the blood and milk compartments at different period of cell maturation, with different killing and chemotactic abilities (Van Merris et al, 2002;Burvenich et al, 2003). The results of this study should also be restricted to the specific E. coli strain P4:O32 used to inoculate the cows because of the differences in susceptibility to phagocytosis among coliform strains (Hogan and .…”

l-Selectin and Chemotaxis Throughout Bone Marrow Granulocyte Maturation in the Bovine

“…In vivo and in vitro experiments in humans demonstrated the presence of receptors for C5a on all BM cell populations that contained granulocyte and monocyte precursors and the up-regulation of the CR3 (CD11b) receptor by C5a (Werfel et al, 1992). Recently, the presence of membrane CR3 receptors already at the promyelocytic stage and an intracellular pool of this receptor in the myelocytic stage were detected in bovine BM cells (Van Merris et al, 2002). This finding suggests that the cells at this stage can upregulate CR3 receptors following C5a stimulation.…”

“…Flow cytometric analysis and light microscopy prove that the isolated cells belong to these populations of the PMNL lineage BM cells, and the technique has proven to be useful for performing functional studies on granulocytes (Van Merris et al, 2002 The objective of this study was to use this BM cell isolation method for providing some insights on L-selectin expression and on the chemotactic response of BM myelocytes, metamyelocytes, band cells, and mature granulocytes in comparison with circulating PMNL.…”