[Significance of the functional activity of antibodies in influenza immunity].

A simple and inexpensive test for mass examination of the functional activity of serum antibodies was developed. The test is based on a kinetic serologic reaction that reflects the time course of changes in antibody titers depending on the time of contact of the tested material with antigen. The curves of serum kinetic titration were processed on a computer by the special programme. As a result, an integral factor, an antibody functional activity index (AFAI) was calculated for each serum sample under study. The titers and AFAI were determined in more than 2,000 healthy persons, patients with influenza A and B, and those immunized with different influenza vaccines. The persons having similar antibody titers were demonstrated to greatly differ in AFAI. The functional activity of antibodies is a more precise marker of protection from influenza than the routine quantitative characteristics of antibodies, i.e. titers. The high baseline AFAI decreased the severity of influenza infection. Live influenza vaccines stimulated the production of antibodies having higher AFAI than inactivated ones. The live influenza strains (candidates for vaccine ones) significantly differed in their ability to stimulate the production of antibodies having a high functional activity.