[Thermodynamic aspects of phagocytosis and thrombosis (author's transl)].

In this paper, thermodynamic considerations are applied to two biological processes, phagocytosis and platelet adhesion, the latter being an important step in thrombosis formation. Simple thermodynamic models in terms of changes of the Helmholtz free energy are presented for the engulfment of bacteria by phagocystic cells, as well as for the attachment of platelets to biomaterial surfaces. The interfacial tensions contained in the expressions for the Helmholtz free energy may be obtained from contact angles, by means of an equation of state approach. The in vitro phagocytosis tests show that hydrophobic bacteria are more readily phagocytized than hydrophilic ones, and the thermodynamic model elucidates the reason for this pattern of behaviour. Preliminary results for two types of platelet adhesion tests are presented. Although there is, in terms of simple thermodynamic considerations, a strong similarity between platelet adhesion and the early stages of phagocytosis, we anticipate that specific interactions will play a larger role in platelet adhesion than in phagocytosis.