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Biomedical subjects

A I Kassis

Publications and source records attributed to A I Kassis.

114 records · Page 7Linked to original sources
PubMedDate not supplied

Preadsorption of radiolabeled monoclonal antibodies to liver and spleen tissues leads to higher tumor-to-normal-tissue ratios.

This study addresses the impact of background activity on the use of radioimmunoconjugates for radioimmunodiagnosis and radioimmunotherapy. Since the liver and the spleen represent organs with preferential nonspecific uptake, we exposed radiolabeled (iodinated and Indium-111 labeled) preparations of monoclonal antibodies to a suspension of fresh liver and spleen cells at physiological temperature and compared their immunoreactivity, in vivo biodistribution, and tumor targeting to those of the same radiolabeled proteins without prior adsorption to this suspension. The biodistribution studies were performed under conditions of high background activity, i.e., shortly after the injection (1 hour) and using a high dose of the protein. Preadsorption of radiolabeled monoclonal antibodies results in a significant decreased uptake in certain normal tissues, i.e., greater contrast between normal and tumor tissues, as demonstrated by the quotient of the two target-to-nontarget ratios (exposed/unexposed antibody) which was greater than one for most of the tissues examined.

Adsorption↗
PubMedDate not supplied

Immunoradiometric assay for antibodies recognizing antigenic gangliosides.

An immunoradiometric assay for monoclonal antibodies (MoAb) recognizing gangliosides as antigens (Ag) is described and exemplified by the determination of the immunoreactive fraction of 125I-radiolabeled monoclonal A2B5 and 3G5 IgM antibodies. The assay was performed in 96-well microtiter plates equipped with cellulose filter membranes, using the antigens extracted from cloned rat insulinoma cells (RINm5F). The selectivity of the assay was demonstrated by studying the interactions of A2B5 and 3G5 with specific Ag and irrelevant gangliosides. The binding of 125I-A2B5 and 125I-3G5 to the RINm5F extract containing Ag exceeded 35% of the total applied radioactivity and depended on the degree of protein damage caused by radiolabeling, whereas irrelevant glycolipids bound 0.4% (s.d. 0.3%) of total applied 125I-3G5 and 1.2% (s.d. 0.3%) of 125I-A2B5 regardless of the initial amount of the radiolabeled MoAb used. Additional support for the specificity of this method was acquired in experiments with the A1D2 IgG antibody that interacts with a glycoprotein expressed by RINm5F cells but not with the gangliosidic antigens present in the same cell line. 125I-A1D2 bound neither Ag (0.47%; s.d. 0.12%) nor brain extracts containing irrelevant gangliosides (0.32%; s.d. 0.17%). The data for the specific MoAb-Ag systems were analyzed using a modified Lineweaver-Burk graph. By plotting the reciprocal of the fraction of specifically bound MoAb versus the reciprocal of the antigen concentration, the immunoreactive fraction was determined. The present method is rapid, convenient, and independent of variability in antigen expression on the cell surface.

Antibodies, Monoclonal↗
PubMedDate not supplied

A simple remote system for the high-level radioiodination of monoclonal antibodies.

We have developed a system for the remote control radiolabeling of monoclonal antibodies (MoAb). The system is simple, inexpensive to assemble, and completely disposable. Reagents are pneumatically manipulated into vials containing Iodogen and an anion exchange resin, wherein iodination and separation of bound from free iodine occur, respectively, and sterilized (by filter) into a final vial. Radiolabeling yields of 38.9 +/- 5.5% were consistently produced with 99.3 +/- 0.2% of the isotope bound to the antibody. These results were not significantly different from those obtained in manual iodinations. However, the radiation dose to the hands of the laboratory worker in the remote mode was reduced at least ninefold. The system is presently being introduced for 300 to 400 mCi 131I iodinations of the anti-ovarian cancer MoAb OC 125 in a Phase I radioimmunotherapy trial.

Antibodies, Monoclonal↗