Differential Endocytosis of T and B Lymphocyte Surface Molecules Evaluated with Antibody-Bearing Fluorescent Liposomes Containing Methotrexate

• Published in: Proceedings of the National Academy of Sciences - PNAS 1982-07, Vol.79 (13), p.4148-4152
• Main Authors: Machy, Patrick, Barbet, Jacques, Leserman, Lee D.
• Format: Article
• Language: English
• Subjects: Ammonium Chloride - pharmacology; Animals; Antibodies; antigens; Antigens, Surface - immunology; B lymphocytes; B-Lymphocytes - drug effects; B-Lymphocytes - immunology; Blasts; Endocytosis; Fluorescence; Fluorescent Antibody Technique; Internalization; Liposomes; lymphocytes B; lymphocytes T; Methotrexate - metabolism; Methotrexate - pharmacology; Mice; Mice, Inbred C57BL; Mice, Inbred CBA; Molecules; Monoclonal antibodies; T lymphocytes; T-Lymphocytes - drug effects; T-Lymphocytes - immunology; Uridine - metabolism
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.79.13.4148

Antibody-bearing fluorescent liposomes containing methotrexate became bound to cells expressing determinants recognized by the antibody. The number of bound liposomes could be evaluated by fluorometry, and the internalization of liposomes was evaluated by the methotrexate-mediated inhibition of radiolabeled deoxyuridine incorporation. The effect of methotrexate transferred from the liposomes into the cells was a function not of the number of liposomes bound but of the nature of the cells and of the target molecules. Liposomes bearing antibodies with specificity for the H-2K or Mr94,000 and 180,000 molecules were much more effective at drug delivery into T than B cells, even though these determinants were expressed by both cell types. B cells were more sensitive to the effect of methotrexate in anti-H-2 I-A and I-E liposomes than in anti-H-2K liposomes. Inhibition of the methotrexate effect by NH4Cl suggested that methotrexate entered the cell by endocytosis of the liposomes. The results are consistent with differential internalization of H-2K, I-A, I-E, and Mr94,000 and 180,000 cell surface molecules by mitogen-stimulated T and B cells.