Antibody receptor blocking

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). 

Fc receptors present on the cell membrane of macrophages, monocytes, granulocytes, lymphocytes, and some other cells may, in theory, non-specifically bind Fc portion of antibodies used for immunolabeling. Typically, blocking endogenous Fc receptors involves using normal serum derived from the same species used to produce the secondary antibody. To block endogenous Fc receptors, incubate sections for 15 30 min with normal serum (2 5% v/v) from the host species of the secondary antibody. 

Fig. 9.1 Immunolocalization of Adenosine Receptor A (FITC, green) in mouse myocardium using mouse monoclonal primary antibody after blocking mouse endogenous immunoglobulins by preincubation with unconjugated Fab fragment Goat Antimouse IgG. Red color accounts for cardiomyocytes and erythrocytes autofluorescence captured under illumination with a filter excit ing the autofluorescence in red spectrum. Nuclei are counterstained with DAPI (blue). Courtesy of Stephanie Grote...

As in the case of other receptor tyrosine kinases like erbB 1 and erbB2, efforts have been directed to identify and develop hiunanized antibodies that block the physical interaction between IGF-IR and its cognate ligands. Although obtained by applying different approaches, these antibodies have been shown in a variety of preclinical systems to specifically bind to the extracellular domain of IGF-IR, preventing downstream signahng. 

Congenital (cretinism) Athyreosis or ectopic thyroid, iodine deficiency TSH receptor-blocking antibodies Absent or present Severe... 

Pietras, R. J., Fendly, B. M., Chazin, V. R., Pegram, M. D., Howell, S. B., and Slamon, D. J. 1994. Antibody to HER-2/neu receptor blocks DNA repair after cisplatin in human breast and ovarian cancer cells. Oncogene 9 1829-1838. 

Antibodies that block the interleukin-2 receptor, thus preventing interleukin-2 from activating T lymphocytes, have also been developed.24,62 These antiinterleukin-2 receptor agents, such as basiliximab (Simulect) and daclizumab (Zenapax), may be helpful in reducing the incidence of acute transplant rejection.13 Antibodies seem to be especially useful in the initial (induction) phase of antirejection treatment because these drugs can delay or supplant the use of more toxic immunosuppressants such as the glucocorticoids and calcineurin inhibitors (cyclosporine and tacrolimus).3,56... 

Polyclonal antibodies have been prepared against partially purified rabbit mammary gland receptors [42-44], and have been used to demonstrate that the receptors really are involved in mediating the biological actions of prolactin. Anti-receptor antibodies that blocked binding of labelled prolactin were able to inhibit prolactin-stimulated casein synthesis and amino acid transport in rabbit mammary gland explants in vitro [43,45] (Fig. 4). They had no effect on the actions of insulin... 

Fig. 4. Antibodies to the prolactin receptor block the actions of the hormone on casein synthesis in rabbit mammary tissue explants. CS, control serum AS, antiserum to receptor P, prolactin. Data from Ref. 45.

More recently, monoclonal antibodies to the rabbit prolactin receptor have been described [49,50]. These showed strong species specificity, competed with 125I-la-belled prolactin for binding to receptors, and provided evidence for receptor heterogeneity in some tissues [49], Two of the monoclonal antibodies could block the actions of prolactin on casein synthesis in rabbit mammary gland explants, and one of them could inhibit milk production in vivo [50]. A third antibody could mimic the actions of prolactin on both casein and DNA synthesis in mammary explants. For this effect bivalency was essential, and down-regulation of receptors was much less than that produced by prolactin itself [50],... 

Certain precautions need to be observed at the outset of this effort. To be an appropriate subject for downsizing, an antibody must achieve critical interactions with at least part of the receptor-binding surface of IL-ip. This is to exclude selection of an antibody that blocks access of IL-1 p to the receptor merely by steric overlap of its molecular bulk with the space occupied by bound receptor (5). Such an antibody, on downsizing, would lead to a compound that fails to compete with IL-ip binding. Here we describe the selection and characterization of an antibody, and its Fab fragment, that provides a suitable starting point for this endeavor. 

CCR3 Antibodies. A specific CCR3 monoclonal antibody, 7B11, blocks binding of eotaxin, MCP-3, and RANTES to the CCR3 receptor, and also blocks chemokine-induced... 

Those fractions containing the immunoactive insulin were pooled, lyophilized and tested for insulin bioactivity in a bioassay which measures the incorporation of 3H-glucose into toluene soluble lipids using adipocytes from male rats. (J 3). The amount of insulin bioactivity recovered from the extract was similar to the amount of immunoactivity obtained in the insulin radioimmunoassay. In addition the bioactivity was almost completely removed in the presence of an excess of anti-insulin antibody as well as by an antibody which blocks the insulin receptor (data not shown) (Figure 5) (4 ). 

Shigemoto. R T. Abe, S. Nomura, S. Nakanishi, and T. Hirano (1994) Antibodies inactivating mGluRl metabotropic glutamate receptor block long-term depression in cultured Purkinje cells. Neuron, 12, 1245-1255. 

Ninety percent of cancer deaths are caused by metastatic rather than primary tumors. Define metastasis. Explain the rationale for the following new cancer treatments (a) batima-stat, an inhibitor of matrix metalloproteinases and of the plasminogen activator receptor, (b) antibodies that block the function of integrins, integral membrane proteins that mediate attachment of cells to the basal laminae and extracellular matrices of various tissues, and (c) bisphosphonate, which inhibits the function of bone-digesting osteoclasts. 

Miyazaki S., H. Shirakawa, K. Nakada, Y. Honda, M. Yuzaki, S. Nakade K. Mikishiba. 1992a. Antibody to the inositol trisphosphate receptor blocks thimerosal-enhanced Ca Mnduced Ca release and Ca oscillations in hamster egg. FEBS Lett. 3 9 180-4. 

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