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

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 of the latex reagent was found at pH values between 8 and 9. At pH 6 the latex reagent becomes unstable, at 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).