Specificity of monoclonal antibody

Because MIB-1 monoclonal antibody is used extensively to determine the cell proliferation index, its applications are discussed below. This antibody detects the nuclear antigen Ki-67 expressed in proliferating cells but not in resting cells. The antibody reacts with the nuclei of cells in mid-Gj (first gap), S (DNA synthesis), G2 (second gap), and M (mitosis) phases, but not in the G0 or quiescent phases. The use of MIB-1 antibody is one of the simplest and most reliable labeling techniques for assessing the rate of proliferation of a neoplastic cell population. Thus, the antibody can be used to assess the growth fraction (i.e., the number of cells in cell cycle) of normal, reactive, and neoplastic tissues. 

However, be aware that in spite of the usefulness of the MIB-1 antibody in assessing the rate of cell proliferation, the classification of cancers (e.g., breast cancer) by the size of the primary tumor and the presence and extent of lymph node metastases does not adequately explain differences in the clinical outcome of individual patients. Cell proliferation indices are commonly used, along with other diagnostic parameters, to estimate the risk of recurrence of a cancer for individual patients. Therefore, it is important to understand the relationship between various indices of proliferation such as MIB-1 labeling index and detection by either in situ hybridization or polymerase chain reaction. This approach will lead to quality assurance in diagnosis. 

To avoid this problem, the application of MIB-1 antibody is useful in the differential diagnosis of benign exophytic vulvar lesions because HPV-associated lesions show 

Note that MIB-1 antibody fails to react with Ki-67 antigen in the tissue fixed with formaldehyde or Kryofix in the absence of heat pretreatment. Because Kryofix is a nonprotein, crosslinking fixative, breakdown of protein crosslinkages is not responsible for the availability of Ki-67 antigen in this case. On the other hand, MIB-1 antibody readily reacts with Ki-67 antigen in tissue fixed with cither of these two fixatives with heat pretreatment. It is apparent that in this case the effect of heat treatment is due to factors other than breakdown of protein crosslinkages. 

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Table VI. Specificity of monoclonal antibodies from immunization with free peptide representing surface regions that are non-antigenic in whole Mb...

Subsequent studies using IFN-y synthetic peptides to map the epitope specificity of monoclonal antibodies to murine IFN-y showed that N-terminal specific monoclonal antibodies neutralize IFN-y antiviral activity [29]. In receptor-... 

Graham, A K, Herrington, C S, and McGee JO D (1991) Sensitivity and specificity of monoclonal antibodies to human papillomavirus Type 16 Capsid protein-comparison with simultaneous viral detection by nonisotopic in situ hybridization J Clin Pathol 44,96-101... 

Because many potentially useful monoclonal antibodies do not possess the appropriate isotype and so are unable to activate human complement and/or trigger Fc-yR on human cells, treatment strategies are needed. One such strategy is the application of bispecific monoclonal antibodies that exploit the specificity of monoclonal antibody and ensure activation of cellular cytotoxic mechanisms (Fanger et al., 1993). 

Table I. Specificities of Monoclonal Antibodies for Various Avermectins. The values are the amount of the indicated compound giving half-maximal inhibition in a competition EIA on plates coated with ivermectin 4 -hemisuccinate-conalbumin (coating antigen 1) or ivermectin-Cg-hemisuccinate-BSA (coating antigen 2) at 25 ng of carrier protein per well. All analogs were approximately 80 20 mixtures of the respective isomers, e.g., Avermectin A2 was a mixture of avermectin A2a avermectin Agb 80 20. Stock solutions of all compounds in methanol were standardized by spectrophotometry (see refs. 14-17 for extinction coefficients and chemical data), and dilutions for assay were made in PBS-Tween-5% methanol. Results are the mean of 8 replicates, and standard errors were approximately 5% of the means. NR = not recognized in amounts up to 10 ppm...

The strategy of the immune system to produce polyclonal antibodies yields two important bonus effects, i.e. the affinity bonus (or avidity) and the specificity bonus , both of which are eliminated by cloning (Sections 8.4 to 8.6). The specificity of monoclonal antibodies may sometimes prove to be not as high as expected. Some may cross-react, and this cross-reactivity cannot, in contrast to polyclonal antisera, be removed with immunosorbents (Brodsky et al., 1979). A monoclonal antibody is unable to distinguish different antigens if they bear the same epitope. For example, Bundesen et al. (1980) encountered this problem with a peptide sequence common to several hormones. Kurstak et al. (1983) emphasized problems with monoclonal reagents in virus diagnosis. 

Another interesting application is the analysis of the specificity of monoclonal antibodies, i.e., whether they recognize different epitopes on the antigen (Friguet et al., 1983). After coating the antigen, two monoclonal antibodies are added, either to separate or to the same well and the amount of bound antibody is quantitated with enzyme-labeled anti-mouse IgG. Additivity of enzyme activity is observed when the monoclonal antibodies bind to distinct epitopes. The additivity index (A/) for a pair of antibodies is then defined as ... 

The specificity of monoclonal antibodies against several types of TCTCs are also shown In Figs. 4 and 5. Several monoclonal antibodies were found to have specificities different from the polyclonal antibodies when the same type of Immunogen was used. 

The specificity of monoclonal antibodies make it possible to develop an analytical method for a single mycotoxin, such as aflatoxin Bi in maize and groundnut meal, or aflatoxin Mj in milk and milk products. Even within chemically closely related structures such as the Fusarium trichothecenes there is very little cross-reactivity between a monoclonal raised to a single toxin such as T-2 toxin and other members of the family. Thus, a monoclonal raised against 3-acetyl-deoxynivalenol showed negligible cross-reactivity with deoxynivalenol, nivalenol, or T-2 toxin. 

Matsuda, T., Ishiguro, H., Ohkubo, I., Sasaki, M. and Nakamura, R. Carbohydrate binding specificity of monoclonal antibodies raised against lactose-protein Maillard adducts. J. Biochem. 1992, 111, 383-387. 

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