Activation of human monocytes and granulocytes by monoclonal antibodies to glycosylphosphatidelinositol‐anchored antigens

Abstract

The present study investigated possible receptor-like characteristics of glycosylphosphatidylinositol (GPI)-linked antigens on human monocytes and granulocytes by measuring cytoplasmic calcium fluxes and the oxidative burst in cells following cross-linking of GPI-linked antigens. Cross-linking of cell-bound anti-CD14, -CDw52 and -CD55 induced cytoplasmic calcium fluxes and oxidative bursts in unprimed human monocytes similar to those observed following Fc gamma R cross-linking. In granulocytes primed with 200 mM N-formyl-Met-Leu-Phe (FMLP), cross-linking of cell-bound anti-CD16, -CD24, -CD59 and -CD67 led to calcium fluxes and activation of the oxidative burst. The oxidative bursts mediated by GPI-linked antigens were stronger than those induced by 200 nM FMLP, even though FMLP induced a larger increase in cytoplasmic calcium concentration. The responses were likely to be independent of Fc gamma R interactions as F(ab')2 fragments of IgG or IgM antibodies were used in the experiments. Activating effects of monoclonal antibody to GPI-linked antigens were not observed in cells from patients with paroxysmal nocturnal hemoglobinuria, which are deficient in GPI-linked antigens. In addition, treatment with GPI-specific phospholipase C led to inhibition of cell activation through GPI-linked antigens but not through transmembrane receptors. Cross-linking of a number of non-GPI-linked antigens (CD11a, CD18, CD31, CD35, CD43, and CD45) neither induced calcium fluxes, nor activated the oxidative burst. The results indicate that most, if not all, GPI-linked surface glycoproteins on myeloid cells are capable of mediating cell activation and suggest that the GPI anchor is a structure facilitating signal transduction.

Neurodegeneration Induced by Clustering of Sialylated Glycosylphosphatidylinositols of Prion Proteins

“…An increasing number of GPI-anchored proteins including CD59 (8), Thy-1 (9), CD14 (10), and Fc-⑀-R1 (11) are associated with cell responses and the activation of multiple cell-signaling pathways. The diversity of responses that follow the engagement of GPI-anchored receptors may reflect diversity in the composition and structure of GPI anchors.…”

“…Although the core of GPI anchors is conserved (7,12), they have variable glycan side chains and lipid moieties, and there is increasing interest in the physiological significance of such variations. Cell activation commonly occurs following cross-linkage of GPI-anchored proteins by antibodies (10,14), suggestive of a density-dependent effect.…”

Pre-B Cell Antigen Receptor-Mediated Signal Inhibits CD24-Induced Apoptosis in Human Pre-B Cells

“…This differentiation-dependent expression pattern has implied a role for CD24 in B cell development, and indeed, several lines of evidence suggest functional involvement of CD24 in B cell development. First, CD24 is known to mediate signal transduction, including phosphorylation of intracellular proteins and intracellular calcium mobilization (13)(14)(15). In addition, cross-linking of CD24 induces apoptosis in mouse B cell precursors (16,17).…”

Peptidoglycan Induces Mobilization of the Surface Marker for Activation Marker CD66b in Human Neutrophils but Not in Eosinophils

“…It is present in the membrane of specific and gelatinase-containing granules of neutrophils, and stimuli such as fMLP induce its mobilization to the cell surface (4,5,7). Cross-linking of CD66b results in cellular responses, for example, respiratory burst and increased adhesion (10). In addition, CD66b has been suggested to serve as a receptor for galectin 3 (5).…”