In vivo distribution of particulate antigens and liposomes in murine spleen. A possible role in the humoral immune response.

Several particulate antigens and liposomes were intravenously injected in mice in order to study their localization patterns in spleen and liver. Liposomes have been proposed as promising carriers for haptens and antigens. It was studied whether the phospholipid composition, cholesterol content and charge of the liposomes played a role in their distribution within the spleen. Different thymus-independent type 1 and type 2 and thymus-dependent particulate antigens as well as liposomes were labeled with the lipophilic fluorochrome Di-I. After labeling they were intravenously injected and spleens and livers were removed at different time intervals and prepared for light- and fluorescence-microscopy. We have observed that all particulate antigens and liposomes administered to the mice localized according to the same distribution pattern in the spleen. After 2 and 4 h particles were located in macrophages of the marginal zone and after 24 h white pulp macrophages had also ingested particulate antigens and liposomes. So we conclude that the distribution of the particulate antigens and liposomes in the spleen is independent of the immunological nature of the particles. Results are discussed with respect to the question whether or not the distribution of particulate antigens and liposome associated antigens or haptens, may be a crucial factor in determining the type of immune response to be elicited.