Latex Particle Agglutination in the Immunochemical System Human Serum Albumin–Anti‐Human Serum Albumin Rabbit Serum

Abstract

The stability of monodisperse polystyrene latex particles in the immunochemical system human serum albumin-rabbit anti-human albumin serum was studied by using a photometric method for the detection of latex particle agglutination. The latex particles were coated with human serum albumin and mixed with dilutions of both a hyperimmune and a normal rabbit serum. The experiments were carried out with latex particles of different size at varying pH, ionic strength and temperature. From the agglutination curves it was possible to derive conclusions on the specific and nonspecific immunochemical interactions with latex particles as well as on the effects of electrolyte coagulation. Maximum sensitivity ofthe latex reagent was found a t pH values between 8 and 9. At pH < 6 the latex reagent becomes unstable, a t pH < 4 the immunochemical interactions disappear, and at pH > 11 the immunochemical reaction becomes indistinct. Thermal inactivation could eliminate some of the nonspecific interactions, but the most efficient method was in experimenting at high ionic strengths ( I = 0.5).Latex particle agglutination methods, having been in use in serologic laboratories for some fifteen years, belong to very sensitive methods for the detection of immunochemical interactions. Since the first report of Singer and Plotz [l] on the use of synthetic polymer latex particles for serologic purposes in the detection of rheumatoid factors, an appreciable number of papers have appeared describing various latex agglutination tests. The predominant part of this work has been connected with the problems of the application of latex tests in serology, as can be concluded from extensive reviews [2,3]. Far less work, however, has been devoted to the study of latex agglutination in well defined immunochemical systems containing only specific antibodies against a given antigen.If a systematic study of latex particle agglutination in immunochemical systems is to be undertaken, one has to choose a model system consisting of a single well characterized antigen and a homologous specific antibody. Renoux [4] was the first, as far as we know, to describe latex agglutination in a model immunochemical system. His work on the system ovalbumin-antiovalbumin, aimed at comparing the sensitivity of the latex agglutination method with the precipitation and passive hemagglutination methods. Renoux only sketched the idea and described a few experiments but did not investigate the influence of a number of important factors which may influence the immunochemical interaction, such as pH, ionic strength, temperature, etc. An extensive work in studying the influence of the variation of several physicochemical parameters on latex particle stability and agglutination was done by Singer and his collaborators [5-101. They experimented, however, with human gamma-globulin coated latex particles and rheumatoid sera, a system much more complex than model systems. For that reason their results are not fully comparable with data obtained on model systems and could be obscured t...

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