title: Intracellular processing of liposome-encapsulated antigens by macrophages depends upon the antigen.
abstract: Two proteins, a recombinant malaria protein (R32NS1) and conalbumin, were encapsulated in separate liposomes. The mechanisms of presentation of unencapsulated and liposome-encapsulated R32NS1 and conalbumin to antigen-specific T-cell clones were investigated in in vitro antigen presentation assays using murine bone marrow-derived macrophages (BMs) as antigen-presenting cells. A much lower concentration of liposomal antigen than of unencapsulated antigen was required for T-cell proliferation. Liposome-encapsulated conalbumin required intracellular processing by BMs for antigen-specific T-cell proliferation, as determined by inhibition with chloroquine, NH4Cl, leupeptin, brefeldin A, monensin, antimycin A, NaF, and cycloheximide and by treatment of BMs with glutaraldehyde. Liposome-encapsulated conalbumin therefore follows the classical intracellular antigen processing pathway described for protein antigens. Similarly, unencapsulated conalbumin also required intracellular processing for presentation to antigen-specific T cells. In contrast, both unencapsulated R32NS1 and liposome-encapsulated R32NS1 were presented to T cells by BMs without undergoing internalization and intracellular processing. These results suggest that the antigen itself is the major element that determines whether a requirement exists for intracellular processing of liposomal antigens by macrophages.
authors.affiliation: Department of Membrane Biochemistry, Walter Reed Army Institute of Research, Washington, D.C. 20307-5100, USA.
authors.forename: M
authors.initials: M
authors.lastname: Rao
authors.forename: N M
authors.initials: NM
authors.lastname: Wassef
authors.forename: C R
authors.initials: CR
authors.lastname: Alving
authors.forename: U
authors.initials: U
authors.lastname: Krzych
mesh_terms: D000595:Amino Acid Sequence; D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology; D000941:Antigens / Q000008:administration & dosage*; D001692:Biological Transport / Q000187:drug effects; D001854:Bone Marrow Cells; D002999:Clone Cells; D003207:Conalbumin / Q000276:immunology; D003513:Cycloheximide / Q000494:pharmacology; D011992:Endosomes / Q000187:drug effects; D005976:Glutaral / Q000494:pharmacology; D006183:H-2 Antigens / Q000276:immunology; D000949:Histocompatibility Antigens Class II / Q000276:immunology; D008081:Liposomes; D008213:Lymphocyte Activation; D008264:Macrophages / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000941:Antigens; D006183:H-2 Antigens; D000949:Histocompatibility Antigens Class II; D008081:Liposomes; D010455:Peptides; D000643:Ammonium Chloride; D003207:Conalbumin; D003513:Cycloheximide; D005976:Glutaral