title: Complement-mediated follicular localization of T-independent type-2 antigens: the role of marginal zone macrophages revisited.
abstract: In this study we demonstrate a hitherto undescribed phenomenon, namely that thymus-independent type-2 antigens (TI-2 Ag) localize in splenic follicles within 1 h after administration. The follicular localization of 2,4,6-trinitrophenyl (TNP)-Ficoll was not antibody mediated. In addition in case of high-dose administration we observed a relatively large amount of TI-2 Ag in marginal zone macrophages. However, after low-dose administration we observed a preferential localization of TNP-Ficoll in the splenic follicles. Detection of TNP-haptenated Ag in cryostat sections of murine spleens was performed with a high-affinity TNP-specific monoclonal antibody conjugated to beta-galactosidase. Within minutes after injection the TI-2 Ag localized in the marginal zone, attached to marginal zone macrophages and B cells. Twenty minutes after injection the Ag was also detected in the follicles and gradually accumulated there until 7 h after injection. Thereafter, the amount of follicular Ag gradually decreased but was still detectable up to 14 days after immunization. The follicular localization of TNP-Ficoll was complement dependent in contrast to the binding to and uptake by marginal zone macrophages. Double staining revealed that Ag was bound by macrophages, B cells and follicular dendritic cells. Haptenated thymus-dependent (TD) Ag localized exclusively in the red pulp macrophages. In vivo macrophage elimination drastically increased the amount of TNP-Ficoll in the follicles, and enhanced the humoral immune response at low doses of Ag. Moreover, complement deprivation of mice abrogated the localization of TI-2 Ag in the follicles, and led to a decreased humoral TI-2 immune response. In conclusion, we demonstrate for the first time that TI-2 Ag localize in follicles. Moreover, the presented results provide further evidence that B cells and follicular localized Ag play an important role in the induction of humoral TI-2 immune responses.
authors.affiliation: Department of Immunology and Medical Microbiology, TNO Medical Biological Laboratory, Rijswijk, The Netherlands.
authors.forename: A J
authors.initials: AJ
authors.lastname: van den Eertwegh
authors.forename: J D
authors.initials: JD
authors.lastname: Laman
authors.forename: M M
authors.initials: MM
authors.lastname: Schellekens
authors.forename: W J
authors.initials: WJ
authors.lastname: Boersma
authors.forename: E
authors.initials: E
authors.lastname: Claassen
mesh_terms: D000818:Animals; D000906:Antibodies / Q000032:analysis; D000955:Antigens, T-Independent / Q000032:analysis* / Q000276:immunology; D003165:Complement System Proteins / Q000502:physiology*; D008264:Macrophages / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D014301:Trinitrobenzenes / Q000276:immunology
chemical_list: D000906:Antibodies; D000955:Antigens, T-Independent; D014301:Trinitrobenzenes; D003165:Complement System Proteins