Christopher D.V. Black

Fc-receptor-mediated targeting of antibody-bearing liposomes containing dideoxycytidine triphosphate to human monocyte/macrophages

Abstract— Liposomes bearing surface‐attached antibody (L‐Ab) molecules can be used for various purposes including the immunospecific delivery of drugs or other materials to antigenic target cells. In this study, L‐Ab were prepared to deliver an anti‐human immunodeficiency virus (HIV) drug, dideoxycytidine triphosphate (ddCTP) to human monocyte/macrophages. Cells of the monocyte/macrophage lineage are an important reservoir of HIV‐1. A mouse monoclonal antibody IgG2a was labelled with 125I and modified using N succinimidyl‐3‐(2‐pyridyldithio)propionate (SPDP) as a heterobifunctional reagent in order to conjugate with liposomes to produce a covalent bond (thioether). SPDP‐modified antibody was incubated with liposomes containing 5 mol% of maleimido phenyl butyrate phosphatidylethanolamine (MPB‐PE) at room temperature (21°C) for 24 h. L‐Ab were separated from free and aggregated antibodies by centrifugation. L‐Ab were characterized by measuring particle size and binding to anti‐mouse IgG‐sepharose. Ninety five per cent of the liposomal (L‐Ab) lipid label was bound to anti‐mouse IgG‐sepharose, whereas only 7% of plain liposomes were bound, indicating non‐specific binding. Uptake of L‐Ab was measured in human monocyte/macrophages as a function of time and compared with that of plain liposomes. The uptake increased with time and it was 4–6 times greater than that of plain liposomes although part of that effect may have been due to unreacted MPB groups.

Lymphatic Delivery of Monoclonal Antibodies: Potential for Detection and Treatment of Lymph Node Metastases

AbstractTwo roads diverged in a wood, and I—I took the one less traveled by, And that has made all the difference.

Induction of IL-2 receptor expression in vivo: Response to concanavalin A

The requirements for the induction of IL-2 receptor expression following lymphocyte stimulation in vitro are well understood but little is known about the role of IL-2 and the IL-2 receptor in lymphocyte activation in vivo. Following the subcutaneous injection of concanavalin A, cells from popliteal and lumbar lymph nodes draining the footpad became enlarged and expressed the IL-2 receptor. At the peak of the response, 9-15 hr after injection, more than 70% of all cells were IL-2 receptor positive; the majority were T cells of both Lyt-2+ and L3T4+ subsets. IL-2 receptor expression was closely associated with both spontaneous and IL-2-driven proliferation. Analysis of the biodistribution of 125I-labeled concanavalin A revealed that much of the injectate remains in the footpad injection site but the mitogen also accumulates in the draining lymph nodes and eventually in the major organs. This model of lymphocyte activation was used to demonstrate that in vivo cyclosporin A inhibits both IL-2 receptor expression and the induction of spontaneous proliferation.

Induction of IL-2 receptor expression in vivo: response to allogeneic cells

Although the requirements for the induction of IL-2 receptor expression following lymphocyte stimulation in vitro have been well characterized, little information is available on the role of IL-2 and the IL-2 receptor in lymphocyte activation in vivo. We have established a quantitative assay for the measurement of IL-2-receptor-positive cells in the draining popliteal lymph node following the injection of allogeneic cells in the footpad. At the peak of the response more than 20% of the lymph node cells were IL-2-receptor-positive, and the majority of the IL-2-receptor-positive cells were Ly-2+ T cells and B cells. IL-2 receptor expression in vivo was closely associated with an increase in cell size and spontaneous and IL-2-driven proliferation, as well as with the induction of CTL activity specific for the donor strain. The model system described here should be useful in the further characterization of the mechanism of action in vivo of immunosuppressive drugs, antibodies, or lymphokines.

Use of Monoclonal Antibodies to Detect Metastases of Solid Tumors in Lymph Nodes

Monoclonal antitumor antibodies provide the possibility of locating breast cancer metastases much smaller than those detectable by current non-invasive techniques. In the case of metastasis to axillary lymph nodes, a sensitive imaging technique might reduce the need for surgery. It might also detect small metastases in the internal mammary node chains, where surgical biopsy is not routinely performed. As an alternative to the more usual i.v. route of administration for monoclonal antibodies, we have been studying delivery via lymphatic vessels for detection of lymph node metastases. Using a metastatic hepatocarcinoma in guinea pigs, we find that subcutaneous injection for uptake by lymphatic capillaries leads to specific localization of antibody in lymph node metastases, as indicated by gamma camera imaging, double-label isotopic tracers, and autoradiography. When lymph nodes are the target, the lymphatic route offers higher efficiency, faster localization, and less systemic toxicity than does the i.v. route. In addition, there may be less cross-reaction with antigen expressed on normal cells.