Effect of Monocyte Locomotion Inhibitory Factor (MLIF) on the Activation and Production of Intracellular Cytokine and Chemokine Receptors in Human T CD4+ Lymphocytes Measured by Flow Cytometry

Abstract

The supernatant of Axenically cultured Enatamoeba histolytica (E. histolytica) produces a thermostable factor that was purified and characterized by high resolution chromatography (HPLC) and mass spectrometry (MS-MS), supplemented by the methods of Edman (Edman & Begg, 1967). This revealed a pentapeptide with a molecular weight of 583 Daltons and established the aminoacid sequence (Met Gln Cys Asn Ser), which was termed Monocyte Locomotion Inhibitory Factor (MLIF). MLIF has powerful and selective antiinflammatory properties, which were established in vitro by Boyden chamber studies. MLIF inhibits locomotion, both random chemokinetic and chemotactic, of mononuclear phagocytes (PM) from normal human peripheral blood but not of neutrophils toward various attractants, such as C5a-Desargues lymphokine and Lymphocyte-derived chemotatic factor (LDCF) (Kretschmer et al., 1985). This factor also depresses the respiratory burst of monocytes and neutrophils activated with zymosan in vitro, as measured by chemiluminescence (Rico et al., 1992), and nitric oxide production in mononuclear phagocytes and human polymorphonuclear neutrophils (PMNs) (Rico et al., 2003). Such effects were not accompanied by changes in expression of CD43, a ligand critical in the initial activity of phagocytes, in the membrane of these cells, and did not affect the viability of phagocytes (Kretschmer et al., 1985). In contrast, MLIF does not affect either locomotion or the respiratory burst of zymosan-activated human PMNs (Rico et al., 1998). In vivo, MLIF delays the arrival of mononuclear leukocytes in Rebuck chambers applied to the skin of healthy human volunteers (Kretschmer et al., 1985), inhibits cutaneous delayed contact hypersensitivity to 1-chloro-2-4-dinitrobenzene (DNCB) in guinea pigs (Gimenez-Scherer et al., 1997) and decreases expression of the adhesion molecules VLA-4 on monocytes and VCAM-1 in the vascular epithelium (Gimenez-Scherer et al., 2000). MILF inhibits the expression induced in inflammatory proteins such as MIP-1┙ and MIP-1β in U-937 cells, which are NF-κB pathway-regulated proteins (Utrera-Barillas et al., 2003). The p65–p50 heterodimer comprises the most abundant form of NF-κB in a PMA-induced system. Temporary studies showed that MLIF induces p50 translocation, which may be explained