Antibody-dependent Effector Cells Research Articles

Improvement of hepatitis B vaccine by the use of a new adjuvant

Humoral and cellular immune responses of mice and guinea-pigs to hepatitis B virus surface antigen when alum-precipitated or administered with Syntex Adjuvant Formulation (SAF) were compared. Two doses of HBsAg in SAF were sufficient to elicit antibody responses, and using SAF the dose of antigen could be reduced to one-tenth of that required to elicit antibody responses by alum-adjuvanted HBsAg. The use of SAF increased and made more consistent the antibody responses in young mice and in strains of mice with inherited low responses to HBsAg. Cellular responses to HBsAg were more consistently observed when SAF was used than when alum was used. SAF increased the formation of IgG2a antibodies in mice except in the B10.M strain; antibodies of this isotype activate complement and act synergistically with antibody-dependent effector cells more efficiently than antibodies of other isotypes. If SAF proves acceptable for human use it could improve vaccines against hepatitis B virus.

An adjuvant formulation that selectively elicits the formation of antibodies of protective isotypes and of cell-mediated immunity

Adjuvants are required to elicit protective immune responses with bacterial toxoids, inactivated viruses and subunit antigens produced by recombinant DNA technology. Some adjuvants, such as muramyl dipeptide (MDP) analog formulations, preferentially induce the formation of antibodies of isotypes that interact with complement and antibody-dependent effector cells, and do not elicit reaginic antibodies. Aluminum salts and mineral oil emulsions increase antibody formation but not cell-mediated immunity (CMI), whereas MDP formulations also elicit CMI. Adjuvants such as MDP and lipopolysaccharide (LPS) stimulate the production by accessory cells of IL-1 that increases the circulation of lymphocytes through draining lymph nodes and act as a growth factor for lymphocytes. Vehicles such as mineral oil emulsions, liposomes and Pluronic polymer formulations provide large surface areas on which antigens can be retained in a two-dimensional matrix, from which they can readily be transferred to antigen-presenting cells. The development of an adjuvant formulation able to elicit the formation of protective antibodies and CMI without unacceptable side effects is described.

Alteration of lymphoid cells in AKR mice by treatment with monoclonal antibody against Thy-1 antigen.

AKR/J mice treated with high levels of monoclonal anti-Thy-1.1 antibody and C' remained healthy without apparent side effects. Examination of the lymphatic organs of these mice demonstrated a selective depletion of T cells in lymph nodes and spleen. Following cessation of treatment of the levels of anti-Thy-1.1 antibody in the circulation fell and the peripheral lymphatic organs gradually became repopulated with T cells. Depletion occurred in lymph nodes whether or not C' was infused along with the antibody. Although the thymocytes of these mice were coated with anti-Thy-1.1 antibody they were not eliminated by the treatment. The elimination of peripheral but not thymic T cells suggests either a thymic barrier to the penetration of cofactors (possibly antibody-dependent effector cells) or that antibody acts by interfering with the normal traffic of peripheral T cells which normally "home" to the lymph nodes and spleen.

Immunotherapy of metastases of human neoplastic cells grown in immunodeficient mice

Hereditarily athymic (nude) and asplenic-athymic (lasat) mice were inoculated neonatally with 107 K-562 pluripotential leukemia cells of human origin. Meningeal infiltration and/or multiple metastases were found in the lungs, kidneys, and lymph nodes in nearly 60% of mice. Twice as many lasat mice as nude mice had meningeal and lymph node infiltrations. This result indicates that the spleen of nude mice influences the infiltrations and/or the distribution of metastases. Metastases of K-562 cells were found as early as 10 days and as late as 115 days of age. Goat immune gamma (γ)-globulin, prepared from antiserum to K-562 cells and absorbed with peripheral leukocytes and bone marrow cells from normal individuals, markedly diminished the incidence of metastases of K-562 cells. About 16% of the mice treated with immune γ-globulin had metastases in the lungs only. All mice receiving the immune γ-globulin had peripheral monocytosis and lymphocytosis as well as a hyperplasia of the bone marrow monocytic series. Immune γ-globulin may lyse heterotransplanted leukemia cells by direct binding to leukemia cells in the presence of complement and/or may activate antibody-dependent effector cells, for example macrophages or killer cells, which would destroy the transplanted leukemia cells.

Cell-Mediated Cytotoxicity Against Virus-Infected Target Cells in Humans

Abstract The mechanisms by which human lymphocytes lyse virus-infected allogeneic fibroblast cultures were analyzed with particular consideration of the role of antiviral antibodies and interferon. Human cells infected with viruses were able to induce high levels of interferon upon contact with human lymphocytes. Interferon, whether produced by lymphocytes after direct infection with virus or induced upon exposure of lymphocytes to virus-infected fibroblasts, appeared to be responsible for enhancing the cytotoxic efficiency of the natural killer cell against the infected target. Activation of cytotoxic lymphocytes occurred as early as 6 hr after addition of interferon and increased up to 24 hr. Antibody-dependent cell-mediated cytotoxicity (Ab-CMC) could be easily induced by sensitization of infected target cells with antiviral antibodies and could be detected at 4 hr from the beginning of the cytotoxic test, before the effect of interferon on the natural killer cell was evident. However, the antibody-dependent effector cell was inactive after 4 hr of incubation. F(ab′)2 fragments of rabbit antihuman IgG completely inhibited Ab-CMC but did not at all affect the spontaneous cytotoxic activity of the effector cells against virus-infected target.

Effector cell involved in cell-mediated cytotoxicity to cells infected with herpes simplex virus type 1

Experiments were performed to analyze the characteristics of the effector cells involved in cell-mediated killing of herpes-infected fibroblasts. Effector cells were fractionated according to adherence and phagocytic properties, and lymphocytes were depleted of T-cells, and EA- and EAC- (antibody-coated bovine erythrocytes and bovine erythrocytes coated with rabbit anti-bovine antibodies and C5-deficient mouse serum, respectively) rosette-forming cells by differential centrifugation. Column passage was used as an alternative to depletion of B-cells and F(c)-receptor-positive cells. Antibody-dependent, cell-mediated cytotoxicity was found to be associated with nonphagocytic cells carrying low-avidity F(c) receptors. Some of these had surface immunoglobulin; others lacked both B- and T-cell markers. Low levels of killing were found without addition of anti-herpes antibody to the test system, and this killing seemed to depend on cells belonging to the same subpopulation as the antibody-dependent effector cells.

Analysis by a plaque assay of IgG- or IgM- dependent cytolytic lymphocytes in human blood.

When monolayers of bovine erythrocytes (Eb) were exposed to purified human blood lymphocytes and either IgG or IgM fractions of rabbit anti-Eb serum, clear zones (plaques) appeared when Eb had been lysed by antibody-dependent effector cells (K cells). IgG-dependent plaque formation was complete by 20 h of incubation, while the IgM-dependent reaction required 40 h. The estimated minimal numbers of plaque forming cells (PFC) were 5.6% (IgG) and 2.0% (IgM) of the added lymphocytes. Inhibition experiments with human IgG or IgM indicated that different immunoglobulin receptors on the effector cells were involved in the two systems. In the IgG system, approximately 50% of the PFC had complement receptors and approximately 30% receptors for Helix pomatia A hemagglutinin (HP). In the IgM system, less than 10% of the PFC had complement receptors, while approximately 60% had HP receptors. The results suggest that a subset of human T cells had IgM-dependent K-cell potential. These cells are different from the majority of the IgG-dependent K cells.

Separate Fc-Receptors for Immunoglobulins IgG2a and IgG2b on an Established Cell Line of Mouse Macrophages

Abstract The specificity of Fc-receptors on IC-21 cells, an established line of mouse peritoneal macrophages with antibody-dependent effector cell activity has been examined. Only IgG2a and IgG2b myeloma proteins bound readily to IC-21 Fc-receptors, the former in nonaggregated as well as aggregated form, the latter only as aggregated complexes. Thus, IgG2a bound in a manner characteristic of classically defined cytophilic antibody, whereas the binding of IgG2b appeared to be mediated by Fc-receptors for antigen-antibody complexes. Evidence is presented in support of the view that IC-21 macrophages possess separate and distinct Fc-receptor sites for these two immunoglobulins.

Thymus-Derived Lymphocytes as Effectors of Cell-Mediated Immunity to Syngeneic and Allogeneic Transplants in the Rat

Abstract The nature of the cells effecting in vitro cell-mediated immunity has been examined and compared in a syngeneic and allogeneic tumor system. The tumors used for these different models were the syngeneic W/Fu rat transplantable lymphoma (C58NT)D, induced by Gross virus, and the allogeneic DMBA#8 cell line derived from a chemically-induced F334 rat mammary carcinoma. In both systems, time course experiments show that cytotoxic effector cells recirculate through the thoracic duct. Maximum cell-mediated cytotoxicity in the lymph occurs at day 7 after immunization, which is close in time to peak cytotoxic activity in the spleen. Since treatment of spleens immunized with the syngeneic or allogeneic cell line with specific anti-T cell serum markedly decreases cytotoxicity, we conclude that the major effector cell is a thymus-derived lymphocyte. We did some experiments to decide whether, in addition to T cell killing, there was antibody-dependent cell-mediated cytotoxicity. In the allogeneic system in particular there was some indication that the antibody-directed mechanism may play a role. Following primary (as well as repeated) immunization, a high proportion of allogeneic sera have the capability of inducing specific tumor target lysis by normal spleen cells. In a few instances, similar but weak antibody activity appeared in syngeneic sera only after a booster injection of tumor cells and if harvested after 30 to 50 days. In the syngeneic system it therefore seems likely that only T cells are concerned in the rejection process following primary inoculation of tumor cells, whereas in the allogeneic systems, in addition to cytotoxic T cells, antibody-dependent effector cells also may be involved in tumor cell destruction. This latter conclusion is supported by the finding that anti-T cell serum completely abrogates cytotoxicity in the syngeneic system, while the inhibition is sometimes incomplete in the allogeneic one.