Tag Archives: affinity

Advantages of two- or polyvalent binding of a receptor to the corresponding ligand in comparison to univalent binding

S. A. Bobrovnik, M. O. Demchenko, S. V. Komisarenko

Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Kyiv;
e-mail: s-bobrov@bk.ru

The features of monovalent and bivalent binding­ of receptors (or antibodies) with a polyvalent ligand (or with an antigen) are considered. It is shown that the rigid connection of the binding­ sites of the receptor brings to high increase of binding affinity for the corresponding ligand, but only in case if its epitopes are fully complementary to both sites of the receptor binding. If not, then there is no advantage of the binding of bivalent receptor before univalent binding. If the binding sites of the receptor are connected by a flexible linker, then regardless of location of epitopes of the corresponding ligand there is the successful fastening of receptor and ligand. Exactly the connection by a flexible linker is used by Nature in most cases at constructing of polyvalent receptors.

Avidity of bivalent antibodies. Problems of its experimental determination and theoretical evaluation

S. A. Bobrovnik, M. A.Demchenko, S. V. Komisarenko

Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Kiyv;
e-mail: s-bobrov@bk.ru

Some problems of experimental determination or theoretical evaluation of antibody avidity are considered. It was shown that in order to determine the fraction of nonoccupied antibodies in their mixture with the excess of the corresponding antigen which is required to estimate avidity the methods should be used which are more sensitive than ELISA. The available methods did not allow determining the avidity of bivalent antibodies because of many reasons. However, in the recent years new methods were suggested that make it possible to evaluate the avidity of bivalent antibodies and that of the receptors which consist of two binding sites connected by a flexible linker of the known length. Thus, there are all possibilities now for determining the avidity of bivalent antibodies in experiments or by theoretical methods.

Obtaining and study of properties of new monoclonal antibodies against human IgE

O. Yu. Galkin1,2, A. A. Savchenko1, K. I. Nikitina1, O. M. Dugan1

1National Technical University of Ukraine “Kyiv Polytechnic Institute”;
2Hema Ltd., Kyiv, Ukraine;
e-mail: alexfbt@mail.ru

The original set of 12 clones of hybridomas, producers of monoclonal antibodies (mAbs) against human IgЕ, has been obtained. The study of biological properties of antibodies has been conducted: their specificity, affinity constant and titer in a cultural medium have been established. The obtained mAbs are directed to the two epitope regions on IgE molecule. The first group of mAbs relates to epitope region, represented by three epitopes (two of them overlap and one that does not overlap with others). The second epitope region is represented by only one epitope.

Avidity of polyreactive immunoglobulins

S. A. Bobrovnik

Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Kyiv;
e-mail: s-bobrov@bk.ru

An analysis of the mechanism of interaction between polyreactive immunoglobulins (PRIG) and antigen was conducted and it was shown that most of the traditional methods of antibody affinity evalua­tion are not applicable for PRIG affinity. The comparative assessment of the mouse and human PRIG avidity against ovalbumin and horse myoglobin and the avidity of specific monoclonal antibodies against ovalbumin have shown that the avidity of PRIG not only is much less than the avidity of monoclonal antibodies but even exceeds it.

Biological and immunochemical properties of polyreactive immunoglobulins

S. A. Bobrovnik, M. A. Demchenko, S. V. Komisarenko

Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Kyiv;
e-mail: s-bobrov@bk.ru

A previously unknown phenomenon of acquired polyreactivity of serum immunoglobulins, which were subject to the effect of concentrated solutions of chaotropic ions, such as KSCN (3.0-5.0 M), low/high pH (pH 2.2-3.0), or heating to 58-60 °C, was originally described by the authors in 1990. Eleven years after that, similar data were published by J. P. Bouvet et al.(2001), which confirmed completely our results concerning the influence of either chaotropic ions or drastic shift of pH on polyreactive properties of immunoglobulins. Our further investigations (1993, 1995, 1998) of polyreactive serum immunoglobulins (PRIG) properties have revealed that the mechanism of nonspecific interaction between PRIG and antigens much differs from the mechanism of interaction between specific antibodies and corresponding antigens. Later we have shown that the increase in PRIG reactivity could be induced in vivo (1999) and PRIG are one of serum components of human or animal sera. Then, it could be suggested that PRIG may perform certain biological functions. Studying PRIG’s effect on the phagocytosis of microbes or on the tumor growth (S. A. Bobrovnik et al., 1995, 1998) have revealed that PRIG may play a certain role in protecting the body from infections and probably may influence the development of various pathological processes. Recently we also found (S. A. Bobrovnik et al., 2014) that IgG PRIG content significantly increases in aged people. These data demonstrate that further investigations of PRIG’s immunochemical properties and study of their biological role in organism protection from various diseases is very important.