Microcalorimetry was adopted to detect the reaction of phytohemagglutinin (PHA) with 20% rabbit red blood cell (RBC), thermokinetics curves and parameters were obtained, so as to evaluate agglutinate activity of PHA objectively from reaction process and thermokinetics character aspect. The results showed that thermokinetics parameters of PHA titrated with 20% rabbit RBC were: K (3.24×10⁵ L•mol^－1) (－32.722 kJ•mol^－1), (－238.548 kJ•mol^－1), (－0.664 kJ•mol^－1•K^－1). The hemoagglutination is exothermic reaction for Heat＞0, and it could progress spontaneously for Gibbs free energy was negative (ΔG＜0), and the reaction was entropy decreasing and driven by enthalpy (ΔH＜0, ΔS＜0, |ΔH|＞|TΔS|), the driving force may be chemical bonding force, Van der Waals force and hydrogen bond interaction, the reaction system kept in stable and ordered condition after agglutination. In conclusion, the admix ampoule microcalorimetry established in this study could be adopted as an effective technique for sensitive, precise, quantitative and consecutive detection of hemoagglutination and other antigen-antibody reactions.

Key words: isothermal titration calorimetry, red blood cell, phytohemagglutinin, agglutination, thermokinetics