Leukocytes lysis

Deposition of urate crystals in synovial fluid results in an inflammatory process involving chemical mediators that cause vasodilation, increased vascular permeability, complement activation, and chemotactic activity for polymorphonuclear leukocytes. Phagocytosis of urate crystals by leukocytes results in rapid lysis of cells and a discharge of proteolytic enzymes into the cytoplasm. The ensuing inflammatory reaction is associated with intense joint pain, erythema, warmth, and swelling. 

The two types of cell-mediated immunity involve basically different types of T cells. In the delayed-type hypersensitivity response, the T cell, TD, that reacts specifically with antigens secretes interleukins (see Box S3A) that attract and activate macrophages or other leukocytes, thereby causing a slowly developing inflammatory response. A second type of T cell, known as the T killer cell, TK, reacts specifically with antigen that is bound to target cells, causing their lysis. 

Acute cellular rejection involves infiltration of macrophages and lymphocytes into the graft and is evident from the necrosis of the parenchymal cells of the graft. The lysis of the parenchymal cells of the transplanted tissue is achieved by the infiltrating leukocytes. Acute cellular rejection may be the product of several mechanisms including cytolytic T-cell-mediated lysis, NK cell-mediated lysis and activated macrophage-mediated lysis. The acute cellular rejection predominantly involves CD8+ T cytolytic cells that kill the grafted tissue. 

Although the blood is an easily accessible tissue to study, because red blood cells outnumber leukocytes by about 1000 to 1 in the peripheral circulation, the analysis of leukocytes by any technique is difficult unless the red cells can be removed. Techniques for removing red cells usually involve either density gradient centrifugation (pelleting red cells and neutrophils, leaving lymphocytes and monocytes behind to be collected from a layer as a peripheral blood mononuclear cell preparation [PBMC]) or differential lysis of red blood cells, leaving intact the more robust lymphocytes, monocytes, and neutrophils. 

For complement-dependent cytotoxicity, a complex cascade of protein binding and cleavage occurs that culminates in final complement mediated effector functions of phagocytosis, recruitment and activation of leukocytes, and osmotic lysis. It has been reported that Rituximab (anti-CD20) utilizes a complement-dependent mechanism for tumor cell destruction [14], If the desired effect of a therapeutic antibody is complement-dependent activity, the isotype subgroup chosen should be one that binds to complement proteins (IgGl or IgG3). 

Chow S, Hedley D, Grom P, Magari R, Jacobberger JW, Shankey TV. Whole blood fixation and permeabilization protocol with red blood cell lysis for flow cytometry of intracellular phosphorylated epitopes in leukocyte subpopulations. Cytometry A 2005 67(1) 4-17. 

Infliximab (Remicade) is a mouse-human chimeric monoclonal antibody that binds to soluble and membrane-bound TNF-a and inhibits binding with its receptors. Infliximab is a complement-fixing antibody that induces complement-dependent and cell-mediated lysis when bound to cell-surface-bound TNF-a. It also induces proinflammatory cytokines, such as IL-1 and IL-6, and enhances leukocyte migration. Infliximab is FDA approved for the treatment of Crohn s disease and rheumatoid arthritis, but it is also in phase trials for the treatment of psoriasis. 

Dallegri F, Ottonello L, Ballestrero A, Dapino P, Ferrando F, Patrone F, Sacchetti C Tumor cell lysis by activated human neutrophils Analysis of neutrophil-delivered oxidative attack and role of leukocyte function-associated antigen 1. Inflammation 1991 15 15-30. 

Borrego F, Ulbrecht M, Weiss EH, Coligan JE, Brooks AG (1998) Recognition of human histocompatibility leukocyte antigen (HLA)-E complexed with HLA class I signal sequence-derived peptides by CD94/NKG2 confers protection from natural killer cell-mediated lysis. J Exp Med 187 813 818... 

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