Influence of temperature on complement-dependent immune damage to liposomes

Abstract

Maximal release of trapped liposomal glucose, in the presence of saturating amounts of liposomal antigen (galactocerebroside), antiserum (anti-galactocerebroside), and complement, was dependent on temperature. At lower temperatures (20–25°C), maximal glucose release was inversely related to liposomal phospholipid fatty acyl chain length (dimyristoyl phosphatidylcholine > dipalmitoyl phosphatidylcholine > distearoyl phosphatidylcholine > sphingomyelin). At higher temperatures (32–35°C) a limiting plateau of glucose release, at approx. 60%, was reached, or approached, by all preparations. Sphingomyelin liposomes still released less glucose than those prepared from other phospholipids, even at 35°C. The titers of antiserum and complement ( ABL 50/ ml and CL 50/ml) were dependent on temperature, and differences based on liposomal phospholipid fatty acyl chain length were observed. Analysis of antiserum and complement-dependence on temperature, and on phospholipid type, revealed that although antibody binding to galactocerebroside undoubtedly was subject to steric hindrance due to interference by surrounding phospholipids at 20–25°C, steric hindrance did not play a major role in blocking antibody binding above 32°C.