Abstract

STATUS OF FUNCTIONALLY ACTIVE COMPONENTS OF C4A AND C4B OF THE HUMAN COMPLEMENT SYSTEM IN THE CHILD POPULATION IN CONNECTION WITH THE IMMUNE RESPONSE TO THE PRESENCE OF BACTERIAL ANTIGENS

Vladimir M. Lakhtin*, Mikhail V. Lakhtin, Elena A. Shmeleva and Alexey M. Vorobiev

Abstract

The analysis of the immune response of a 3-4-year-old child population to cell wall polysaccharides and the protein toxoid of Corynebacterium diphtheriae was performed by determining the functionally active isotypes C4A and C4B of human complement system component C4 in a micropanel in the reaction of inhibition of covalent binding of activated C4b to IgG (in the case of C4A) or lipopolysaccharide (in the case of C4B). The different efficacy of C. diphtheriae antigens in inhibiting the formation of C3/C5 convertase (EC 3.4.21.43) from C4A and C4B has been shown. The binding of the activated fragment C4b was judged by the activity of C3/C5 convertase, that is, by the amount of bound to the antigenic target, determined using a conjugate of monospecific polyclonal IgG rabbit antibodies with peroxidase. The polysaccharide antigen inhibited the formation of convertase from the C4B isotype, and the protein antigen inhibited the formation of convertase from the C4A isotype. The incidence of C4A and C4B deficiencies in children with high, medium, and low levels of antitoxic and antibacterial IgG antibodies to C. diphtheriae differed from the normal population. At the same time, C4A deficiencies were correlated with a decrease in anti-toxic immunity, while C4B deficiencies were correlated with a decrease in antibacterial immunity. The results are important for predicting the resistance of the child population to the emergence and development of socially significant diseases. They are also useful for standardizing vaccine preparations and will contribute to further progress in determining the network activities of multifunctional proteins in the defense systems.

Keywords: complement system; deficiencies of С4А and С4В; C3/C5 convertase; ELISA; functional analysis of protein; diphtheria antigens; vaccine, immune reply.