Antibody, monoclonal

Monoclonal antibodies are also becoming increasingly available, and have great potential in the rapid detection of micro-organisms. The use of this method at present is limited by the small number of antibodies available. 

There are other chemical methods used for the estimation of fungi, but they are not in widespread use and are rarely found outside research laboratories. 

The counting of micro-organisms raises a number of serious problems. These include  

British Pharmacopoeia, British Pharmacopoeia Commission, HMSO, London, 1988. 

Pettipher, R.G. Kroll, L.J. Farr, and R.P. Betts, in DEFT Recent Developments for Food and Beverages , Rapid Microbiological Methods for Foods, Beverages and Pharmaceuticals , Society for Applied Bacteriology, Vol. 25. ed. C.J. Stannard, S.B. Petitt and F.A. Skinner, Blackwell Scientific Publications, 1989. 

A monoclonal antibody is an antibody (immunoglobulin molecule) that is produced by recombinant DNA technology this results in all molecules being identical in structure. These monoclonal antibodies are of high purity and are produced in sufficiently large quantities for use as therapeutic agents. 

Antibody (brand name) FDA approval date Type of monoclonal antibody Size (kDa) Volume of distribution Elimination half life How administered (systemic availability) Target Use 

Abciximab (ReoPro) 1994 Chimeric 47.6 8.4 L 0.1 6-0.5 h (but remains on platelets for weeks) IV injection and infusion (1.0) Inhibits platelet aggregation by targeting glycoprotein lib/ Ilia receptor Prevention of thrombosis in percutaneous coronary intervention 

Adalimumab (Humira) 2002 Fully human 144 4.7-6 L 10-20 days SC (0.64) TNF-a Rheumatoid arthritis other autoimmune diseases 

Alemtuzumab (Campath) 2001 Humanized 145 0.18Lkg- Non-linear elimination, 12 days at steady state IV infusion (1.0) CD 52 on lymphocytes Chronic (B cell) lymphocytic leukemia 

B-lymphocyte. However, it was found that antibody-secreting cells cannot be maintained in a culture medium. 

Cell Fusion Unlike antibody-secreting cells, myeloma cells, malignant tumor cells of the immune system, can be cultured continuously. Kohler and Milstein (1975) developed a method to fuse (hybridize) B-lymphocytes from the mouse spleen with mouse myeloma cells, so that the fused cell, hybrid-myeloma (or hybridoma) cell, can have the characteristic of the both cell lines that is, the production of specific antibodies and the immortality. Since the hybridoma is derived from a single B-lymphocyte, it produces only one kind of antibody, thus a monoclonal antibody. 

Inject a chosen antigen into a mouse. The immune system in the mouse responds by proliferating B-lymphocyte cells that secrete antibodies. 

Cultivate a suitable malignant myeloma cells deficient in HPGRT (hypoxanthine guanine phosphoribosyl transferase), which is a genetic marker for the selection of the hybrid cells after fusion. 

Fuse the B-lymphocyte cells with myeloma cells by mixing them in a medium containing 40 percent to 50 percent polyethylene glycol (PEG). The medium will contain the mixtures of B-lymphocytes, myelomas, and hybrid-myeloma cells. The B-lymphocytes contain 

7 Vascular Endothelium in Inflamed Tissue as a Target for Site Selective Delivery of Drugs 

Early in the twentieth century, Ehrlich, from his tissue staining experience, had postulated that if a dye could be made that directly targeted a specific disease-causing organism that perhaps a toxin could be made to accompany the dye and 

Although the development of monoclonal antibody technology may seem a long step from the vision of a student Ehrlich, face and hands covered with biological stains, this cornerstone of modem rmmunochemistry may never have happened if it were not for Ehrlich s dream—a dream now come trae [39]  

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Immunoaffinity chromatography utilizes the high specificity of antigen—antibody interactions to achieve a separation. The procedure typically involves the binding, to a soHd phase, of a mouse monoclonal antibody which reacts either directly with the protein to be purified or with a closely associated protein which itself binds the product protein. The former approach has been appHed in the preparation of Factor VIII (43) and Factor IX (61) concentrates. The latter method has been used in the preparation of Factor VIII (42) by immobilization of a monoclonal antibody to von WiHebrand factor [109319-16-6] (62), a protein to which Factor VIII binds noncovalenfly. Further purification is necessary downstream of the immunoaffinity step to remove... 

Thus, if theantibody has a high affinity for the antigen, it has a high association constant. Typical association constants range from lO to 10 ° L/mol, and as high as 10 L/mol for some monoclonal antibodies. 

The conjugation of monoclonal antibodies (MoAbs) to radioisotopes, chemotherapeutic agents, and protein toxins has also been given consideration (65). Large amounts of human MoAbs can be produced by biotechnological means. 

Nonspecific immunosuppressive therapy in an adult patient is usually through cyclosporin (35), started intravenously at the time of transplantation, and given orally once feeding is tolerated. Typically, methylprednisone is started also at the time of transplantation, then reduced to a maintenance dose. A athioprine (31) may also be used in conjunction with the prednisone to achieve adequate immunosuppression. Whereas the objective of immunosuppression is to protect the transplant, general or excessive immunosuppression may lead to undesirable compHcations, eg, opportunistic infections and potential malignancies. These adverse effects could be avoided if selective immunosuppression could be achieved. Suspected rejection episodes are treated with intravenous corticosteroids. Steroid-resistant rejection may be treated with monoclonal antibodies (78,79) such as Muromonab-CD3, specific for the T3-receptor on human T-ceUs. Alternatively, antithymocyte globulin (ATG) may be used against both B- and T-ceUs. 

Fig. 6. General reaction scheme for the preformed chelate approach where Bz = benzoyl and MAb = monoclonal antibody.

A critical step in radioprotection involves the IL-1 receptors. Monoclonal antibodies to the type 1 IL-1 receptor block IL-l-induced radioprotection (167). Although this receptor is not present on BM cells, it is present on fibroblasts, which suggests that the effects of IL-1 on stem cells maybe largely indirect and mediated by stromal cell activation (168). Anti-IL-1 receptor (type 1) also sensitizes normal mice to the effects of TBI, which suggests that endogenous IL-1 has an intrinsic radioprotective role. IL-6 induction by IL-1, but not CSF levels, is inhibited, which supports the concept that G-CSF and GM-CSF are insufficient by themselves at radioprotecting stem cells and indicates a contributory role for IL-6. Anti-IL-6 antibody blocks IL-1 and TNF-induced radioprotection and also decreases the intrinsic radioresistance of mice, as does anti-TNF- a (169). 

Whereas epidermal growth factor (EGF) enhances the radiosensitivity of human squamous ceU carcinoma cells in vitro (197), addition of EGF to hormone-deprived MCE-7 breast cancer cells prior to irradiation results ia iacreased radioresistance (198). An anti-EGE-receptor monoclonal antibody blocks the abiUty of EGE to enhance growth and radioresistance. Tumor cells, the growth of which is stimulated by EGE, appear to be protected those where growth is iohibited are sensitized (198). 

A two-site immunometric assay of undecapeptide substance P (SP) has been developed. This assay is based on the use of two different antibodies specifically directed against the N- and C-terminal parts of the peptide (95). Affinity-purified polyclonal antibodies raised against the six amino-terminal residues of the molecule were used as capture antibodies. A monoclonal antibody directed against the carboxy terminal part of substance P (SP), covalently coupled to the enzyme acetylcholinesterase, was used as the tracer antibody. The assay is very sensitive, having a detection limit close to 3 pg/mL. The assay is fiiUy specific for SP because cross-reactivity coefficients between 0.01% were observed with other tachykinins, SP derivatives, and SP fragments. The assay can be used to measure the SP content of rat brain extracts. 

Va.ria.tions in Methods. The various immunochemical methods can differ in a number of ways. For example, the analytical reagent may be cmde antisemm, monoclonal antibodies, isolated immunoglobulin fractions, etc. The conditions under which the method is mn, detection of the antigen—antibody complex, and the techniques used to increase sensitivity or specificity of the reaction all maybe varied. 

To date, the most extensively studied polyboron hydride compounds in BNCT research have been the icosahedral mercaptoborane derivatives Na2[B22H22SH] and Na [(B22H22S)2], which have been used in human trials with some, albeit limited, success. New generations of tumor-localizing boronated compounds are being developed. The dose-selectivity problem of BNCT has been approached using boron hydride compounds in combination with a variety of deUvery vehicles including boronated polyclonal and monoclonal antibodies, porphyrins, amino acids, nucleotides, carbohydrates, and hposomes. Boron neutron capture therapy has been the subject of recent reviews (254). 

Product formation kinetics in mammalian cells has been studied extensively for hybridomas. Most monoclonal antibodies are produced at an enhanced rate during the Gq phase of the cell cycle (8—10). A model for antibody production based on this cell cycle dependence and traditional Monod kinetics for cell growth has been proposed (11). However, it is not clear if this cell cycle dependence carries over to recombinant CHO cells. In fact it has been reported that dihydrofolate reductase, the gene for which is co-amplified with the gene for the recombinant protein in CHO cells, synthesis is associated with the S phase of the cell cycle (12). Hence it is possible that the product formation kinetics in recombinant CHO cells is different from that of hybridomas. 

Ricin [9009-86-3], a phytotoxin found in the seeds of the castor oil plant Acinus communis, conjugated to murine monoclonal antibody (Immunogen Corp.), has been approved by the U.S. Food and Dmg Administration (FDA) for the treatment of patients with B-ceU leukemia and lymphoma (59). 

Mammalian Cells Unlike microbial cells, mammalian cells do not continue to reproduce forever. Cancerous cells have lost this natural timing that leads to death after a few dozen generations and continue to multiply indefinitely. Hybridoma cells from the fusion of two mammalian lymphoid cells, one cancerous and the other normal, are important for mammalian cell culture. They produce monoclonal antibodies for research, for affinity methods for biological separations, and for analyses used in the diagnosis and treatment of some diseases. However, the frequency of fusion is low. If the unfused cells are not killed, the myelomas 1 overgrow the hybrid cells. The myelomas can be isolated when there is a defect in their production of enzymes involved in nucleotide synthesis. Mammahan cells can produce the necessary enzymes and thus so can the fused cells. When the cells are placed in a medium in which the enzymes are necessaiy for survival, the myelomas will not survive. The unfused normal cells will die because of their limited life span. Thus, after a period of time, the hybridomas will be the only cells left ahve. 

Commercial use of cell and tissue culture continues to expand. Improvement of organisms through recombinant nucleic acid techniques has become commonplace. Formerly, a few laboratories were well ahead of most others, but now the methods have been perfected for routine use. Another technique that is widely practiced is culturing of cells that excrete high concentrations of just one antibody protein. The specificity of antibodies and antigens is exploited in medical testing procedures using these pure monoclonal antibodies. 

S-Fl Jung, I Pastan, B Lee. Design of interchain disulfide bonds m the framework region of the Fv fragment of the monoclonal antibody B3. Pi otems 19 35-47, 1994. 

Refined structure of an intact IgG2a monoclonal antibody. Biochemistry 36 1581-1597, 1997. 

Figure 17.2 An example of prediction of the conformations of three CDR regions of a monoclonal antibody (top row) compared with the unrefined x-ray structure (bottom row). LI and L2 are CDR regions of the light chain, and HI is from the heavy chain. The amino acid sequences of the loop regions were modeled by comparison with the sequences of loop regions selected from a database of known antibody structures. The three-dimensional structure of two of the loop regions, LI and L2, were in good agreement with the preliminary x-ray structure, whereas HI was not. However, during later refinement of the x-ray structure errors were found in the conformations of HI, and in the refined x-ray structure this loop was found to agree with the predicted conformations. In fact, all six loop conformations were correctly predicted in this case. (From C. Chothia et al.. Science 233 755-758, 1986.)...

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