Chemotaxis Mononuclears

Immunoglobulins (Igs) can activate the complement system, which amplifies the immune response by enhancing chemotaxis, phagocytosis, and release of lymphokines by mononuclear cells that are then presented to T lymphocytes. The processed antigen is recognized by the major histocompatibility complex proteins on the lymphocyte surface, resulting in activation of T and B cells. 

The chemotaxis of mononuclear leukocytes and the migration, growth, and activation of the multiple cell types within atherosclerotic lesions are critical for the chronic inflammatory and fibroproliferative response in atherosclerosis (Ml). Chemokine-mediated attraction of leukocytes to tissues has been shown in atherosclerotic lesions (G8). Studies using knockout and transgenic murine models indicated that chemokine receptor/ligand interactions are crucial in the development of atherosclerosis (P6). Moreover, chemokines may also interfere with smooth muscle cell migration and growth, and platelet activation and other well-defined features of the atherosclerotic process (A2). 

Horwitz, D. A. and Garrett, M. A. (1971). Use of leukocyte chemotaxis in vitro to assay mediators generated by immune reactions. I. Quantitation of mononuclear and polymorphonuclear leukocyte chemotaxis with polycarbonate (nuclepore) filters. J. Immunol. 106, 649-655. 

ND, not determined +, stimulatory —, inhibitory 0, none MLCT, mononuclear leukocyte chemotaxis. 

Early studies suggested that IL-1 and TNF were chemotactic for PMN. However, it has become apparent that this activity resides in a family of molecules of 10 kDa, called neutrophil activating peptides (NAP) or IL-8 (L15). IL-1 and TNF induce the release of these molecules from mononuclear cells, fibroblasts, endothelial cells, and keratinocytes and they act on a specific receptor expressed by PMN. The main activity ascribed to these molecules is PMN chemotaxis, but the molecules may cause oxygen radical and enzyme release by PMN and mobilize PMN into the circulation. The common feature that identifies members of this family of peptides is alignment of four cysteine residues. IL-8 is the most potent chemotactic member of this family. Synthesized as a 99-amino-acid precursor, lL-8 is released as a 79-amino-acid molecule, IL-8a, which itself is further cleaved to 77- and 72-amino-acid forms, IL-8P and IL-8y. IL-8y is predominantly found to be associated with macrophages and may reflect the proteolytic enzymes released by macrophages. Receptors for IL-8 have been identified on PMN and approximately 20% of lymphocytes. The three-dimensional structure of IL-8 (NAP-1) has been reported (C27). 

Snyderman R., Altman, L.C., Hausman, M.S. and Mergenhagen, S.E. (1972). Human mononuclear leukocyte chemotaxis a quantitative assay for humoral and cellular chemotactic factors./. Immunol. 108, 857-860. 

Traves SL, Culpitt S, de Matos C, Russell RE, Barnes PJ, Donnelly LE. Peripheral blood mononuclear cell chemotaxis to MCP-1, GRO-a and IL-8 in COPD [abstr.]. Am J Respir Crit Care Med 2001. In press. 

If using peripheral blood mononuclear cells (PBMCs) or suspension cell fine, sucfi as THPl for monocytes or Jurkat cells for T lympfiocytes, some cfianges need to be made to the chemotaxis protocol. 

Piperidinyl-Amides. Merck has described a compound dass broadly centered around a piperidinylamide linked to a heteroaromatic spacer [88-90]. Affinities ( I-CXCLIO) and functional activities (chemotaxis, CXCLIO) are reported to be as low as 1 nM. Arbitrarily selected members are pyridine 33 [90], thiazole 34 [89] and thiazole 35 [88]. One publidy described member of the thiazole class is coded MRL-957 with, however, undisdosed structure. In peripheral blood mononuclear cells expressing hCXCR3, MRL-957 efficiently blocks chemotaxis by CXCLIO (ICso = 6.9nM) and CXCLll (ICso = 57.4nM) [42]. 

Although one could once generalize that CXC chemokines were chemoattractive for neutrophils and CC chemokines acted on mononuclear cells, a more refined picture is becoming apparent as additional chemokines are tested and characterized. Recent studies suggest that chemokines can stimulate the chemotaxis of specialized subsets of mononuclear cells. Chemoattractants specific for subsets of lymphocytes andfor eosinophils and basophils are described below. 

In the inflammatory response the cellular component can be said to begin with directed migration of phagocytic cells, both polymorphonuclear leukocytes (PMN s) and mononuclear monocytes (MC s) and macrophages (HP s). This process is termed chemotaxis and depends upon signals received at the cell surface which are translated into cellular motility dependent upon actin/myosin polymerization near the cell membrane (Stossel, 1975). In PEM patients in both Peru (Freyre et al., 1973) and Thailand (Kulapongs et al.,... 

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