Monoclonal antibodies lymphocytes

It is relevant to explain the use of the letters CD as a prefix to monoclonal antibodies. Lymphocytes possess many different surface proteins, each of which possesses many distinct epitopes. To classify these lymphocyte antigens, a numbering system has been established that clusters molecules having similar epitopes. Thus, all monoclonal antibodies that detect the epitopes on a single antigen are assigned to a numbered cluster of differentiation (CD). In most cases a defined CD denotes a protein of specific function. For example, the protein called CD4 is associated with cells (lymphocytes) that help the immune response, while CD8 is found on cells that suppress the immune response. 

A B lymphocyte is a specific type of white blood cell (leucocyte) derived from bone marrow stem cells. Each B lymphocyte expresses an immunoglobulin (antibody) specific for a particular antigen. Following antigenic stimulation, a B lymphocyte may differentiate and multiply into plasma cells that secrete large quantities of monoclonal antibody. 

Cytokines. Figure 1 Inhibition of cytokine synthesis during activation of the specific immune system. The monoclonal antibodies Muromonab and Basiliximab are specific for the CD3 complex of the T-cell receptor, and for the IL-2 receptor on lymphocytes, respectively. Cyclosporin and Tacrolimus inhibit activation of cytoplasmic NF-AT, a transcription factor essential for activation of the IL-2 gene ( NFAT Family of Transcription Factors). Sirolimus interferes with mTOR signaling and inhibits IL-2 dependent proliferation. Red pharmaka, blue target proteins. 

Monoclonal antibodies (mAh) are molecules that recognize and bind a specific foreign substance called an antigen. They are produced from a single clone of B lymphocytes. Conventionally, mouse mAh have been generated for experimental and diagnostic use. Techniques have been developed to humanize mouse mAh to facilitate their therapeutic use in humans. It is also now possible to make mAh which are fully human. 

Muronomab-CD3 is a murine monoclonal antibody directed against the CD3 complex of the T-lymphocyte antigen receptor. This drug selectively diminishes the T-lymphocyte pool resulting in a strong lymphopenia. Similar to other nonhuman antibodies the generation of human antimurine antibodies (HAMA) limits its long-term use. 

Murine monoclonal antibodies reacting with CD4, which is solely located on T-helper lymphocytes and monocytes/macrophages, may also be suited for immunosuppression. 

This is a humanized anti-CD52 monoclonal antibody. At present it is in clinical use after bone marrow transplantation and for the treatment of refractory chronic lymphocytic leukemia. 

The chimeric human/murine (basiliximab and dacluzi-mab) or murine (inolimomab) monoclonal antibodies are specifically directed against a part (CD25) of the interleukin-2 (IL-2) receptor. Binding of one of these antibodies to CD25 thereby displaces physiological IL-2 and prevents proliferation of activated T-lymphocytes. 

CK Creatine phosphokinase CKMB The myocardial-specific isoenzyme of creatine phosphokinase Cl The chemical symbol for chloride CL Chemiluminescent CLA Cutaneous lymphocyte antigen CL18/6 Anti-ICAM-1 monoclonal antibody... 

Basiliximab and daclizumab are considered monoclonal antibodies. Daclizumab is a humanized antibody that is approximately 10% murine and 90% human, whereas basiliximab is a chimeric antibody that is approximately 30% murine and 70% human.9,11 These agents bind with high affinity to the IL-2 receptor, where they act as CD25 receptor antagonists. These receptors are present on almost all activated T cells. Their role in induction therapy involves inhibiting IL-2-mediated activation of lymphocytes, which is an important step for the clonal expansion of T cells. 

Rituximab is a monoclonal antibody to the CD20 receptor expressed on the surface of B lymphocytes the presence of the antibody is determined during flow cytometry of the tumor cells. Cell death results from antibody-dependent cellular cytotoxicity. The pharmacokinetics of rituximab are best described by a two-compartment model, with a terminal half-life of 76 hours after the first infusion and a terminal half-life of 205 hours after the fourth dose.36 Rituximab has shown clinical activity in the treatment of B-cell lymphomas that are CD20+. Side effects include hypersensitivity reactions, hypotension, fevers, chills, rash, headache, and mild nausea and vomiting. 

Rituximab (Rituxan ) Rituximab is a chimeric monoclonal antibody directed against the CD20 molecule on B lymphocytes.21 Similar to other B-cell malignancies, CLL... 

The discovery of monoclonal antibodies and combining them with polymeric prodrugs is the newest approach to overcome the lack of selectivity for disposition in target tissue (23). Recently the selectivity of antibody-targeted polymeric anthracycline antibiotics to T lymphocytes was accomplished (25). In addition decreased immunogenicity of proteinaceous conjugates with IgG and human transferrin has been reported (26). 

Rituximab -monoclonal antibody to CD20 (B-cell surface antigen) -fever, chills, malaise -nausea, vomiting -flushing -bronchospasm, angioedema, urticaria -rhinitis -pain at disease sites -tumor lysis syndrome may occur in patients with high peripheral lymphocyte count... 

Feller, A.C., Parwaresch, M.R., Wacker, H.-H., Radzun, H.-J., and Lennert, K. (1983) Combined immu-nohistochemical staining for surface IgD and T-lymphocyte subsets with monoclonal antibodies in human tonsils. Histochem. J. 15, 557-562. 

Monoclonal antibody technology entails isolation of such B-lymphocytes, with subsequent fusion of these cells with transformed (myeloma) cells. Many of the resultant hybrid cells retain immortal characteristics, while producing large quantities of the monospecific antibody. These hybridoma cells can be cultured long term to effectively produce an inexhaustible supply of the monoclonal antibody of choice. 

Mabcampath (EU) or Campath (USA) alemtuzumab a humanized monoclonal antibody directed against CD52 surface antigen of B-lymphocytes) Millennium ILEX (EU) Berlex, ILEX Oncology Millennium Pharmaceuticals (USA) Chronic lymphocytic leukaemia... 

An obvious strategy for overcoming the immunogenicity problem would be the generation and use of monoclonal antibodies of human origin. This is possible but difficult. Human antibody-producing lymphocytes can potentially be rendered immortal by ... 

Bertotto, A., et al. Activation of cord T lymphocytes. II. Cellular and molecular analysis of the defective response induced by anti-CD3 monoclonal antibody, Cell. Immunol., 127, 247, 1990. 

Lymphocytes, the effector cells of the acquired immune system, include morphologically indistinguishable T and B cells, the former divided into CD4+ T helper cells and CD8+ cytotoxic T cells. Since the functions of those cell subsets differ so drastically, it became important to develop tools to distinguish them from each other. Efforts to identify cell subsets according to their expression of different surface antigens have been successful, including various Cluster of Determination (CD) markers (Table 23.1). In addition, cross-reactive monoclonal antibodies, and subsequently developed species-specific polyclonal and monoclonal antibodies towards the major histocompatibility complex (MHC) have been used to label cells in circulation and in tissue sections (Table 23.1). 

De Guise, S. et al., Phenotyping of beluga whale blood lymphocytes using monoclonal antibodies, Develop. Comp. Immunol., 21, 425, 1997. 

The development of techniques for the production of monoclonal antibodies by Kohler and Milstein has enormously expanded the potential of antibodies as analytical and therapeutic agents. A monoclonal antibody is one that is produced by a clone of cells all derived from a single lymphocyte. Any lymphocyte can probably produce only a single immunoglobulin and hence the antibody produced by a clone of identical cells is very restricted in the antigens to which it will bind, making it a very specific reagent. 

The hybridoma cells are initially grown in a medium that will not maintain the growth of the cancer cells these therefore die, as do non-fused lymphocytes, leaving only the fused cells. As the hybridoma cells grow, the supernatant fluid is tested for the presence of antibodies. Those cultures producing the desired antibody are further cloned and either grown in bulk or as tumours in animals and the monoclonal antibodies harvested. 

As they differentiate into populations with differing functions, B and T cells acquire molecules on their surfaces that reflect their specializations. It is possible to produce homogenous antibodies of a single specificity, termed monoclonal antibodies, which can recognize such surface markers. When laboratories from all over the world compared the monoclonal antibodies they had raised, it was found that clusters of monoclonal antibodies were recognizing the same molecule on the surface of the lymphocyte. Each surface molecule so defined was referred to as a CD molecule (Table 2), where CD refers to a cluster determinant. 

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