Lymphoma Target Cells Research Articles

Lymphocyte function-associated antigen 1 (LFA-1): a surface antigen distinct from Lyt-2,3 that participates in T lymphocyte-mediated killing.

Monoclonal antibodies (MAb) have been used to probe the relationship of cytolytic T lymphocyte (CTL) surface molecules to CTL function. Rat MAb to mouse CTL were generated. Twelve MAb so obtained gave preferential binding to T cells as compared to B cells, and three of these recognized previously undescribed surface polypeptides. These Mab and more broadly reactive and previously obtained MAb were tested for their ability to block CTL-mediated killing in the absence of complement. To ensure that any observed blocking was due to binding of MAb to the effector cell rather than the target cell, a xenogeneic mouse CTL anti-rat BN lymphoma target cell system was utilized (MAb and target cells both of rat origin). Of 24 MAb tested here, 21 had little or no effect on CTL function, including those to H-2, Thy-1, Lyt-1, Ly 5, Ly 6, Lgp 100, and at least six other defined antigens. We confirmed inhibition of killing with two MAb to Lyt-2,3. Another MAb, M7/14, gave profound and consistent blockade of CTL function. It was confirmed that M7/14 MAb blocks killing by binding to the mouse CTL and does not bind to the rat lymphoma target cells used for the CTL assay. The findings suggest that the antigen defined by M7/14, termed a lymphocyte function-associated antigen, LFA-1, participates in or is closely associated with the mechanism of CTL-mediated killing. LFA-1 contains two polypeptide chains of 180,000 and 95,000 Mr and is distinct from other described lymphocyte glycoproteins. LFA-1 thus represents both a previously undescribed lymphocyte surface antigen and molecular site for blockade of CTL-mediated killing.

In vitro induction of tumoricidal and suppressor macrophages by lymphokines: possible feedback regulation.

Proteose-peptone-induced macrophages (pM phi) from C57BL/6 (B6) mice were treated in vitro with lymphokine, and 2 functions were evaluated: the ability to suppress lymphokine production and the cytotoxic capacity against tumor target cells. When 10% to 20% pM phi treated with lymphokine were added to a lymphokine-producing system, strong inhibition of MIF and MAF production occurred. The suppression was not specific, since pM phi inhibited the production of lymphokine obtained by either mitogenic stimulation of normal spleen cells (NSC) or alloantigen stimulation of immune spleen cells (ISC). The suppressor cells were adherent, phagocytic, Thy 1.2 negative, with monocyte-macrophage-like morphology. Lymphokine-treated pM phi were also tumoricidal when tested in 18 hr microcytotoxicity assay against RL male 1 lymphoma target cells. However, using endotoxin-free reagents (less than or equal to 0.01 ng/ml of endotoxin by the LAL assay), we found that small amounts of lipopolysaccharide (LPS) were required, in addition to lymphokine, to induce tumoricidal activity in pM phi. In contrast, noncytotoxic pM phi stimulated with lymphokine alone were also able to inhibit lymphokine production, although not as effectively as pM phi stimulated by lymphokine plus LPS. Therefore, we concluded that lymphokine treatment itself is sufficient to induce M phi to become suppressor cells, whereas an additional signal is necessary to induce cytolytic activity. We suggest that there is a negative feedback mechanism of control on the lymphokine-producing cells through the activation of suppressor M phi by lymphokine.

Blocking effect of lyt-2 antibodies on T cell functions.

Monoclonal anti-Lyt-2 antibodies blocked effector function of cytotoxic thymus-derived (T) cells in the absence of added complement. Cytolysis of both allogeneic cells and syngeneic lymphoma or sarcoma target cells was inhibited at the level of the effector lymphocytes. Anti-Lyt-1 and anti-Thy-1 antibodies did not block killer cells. Proliferation of T cells in mixed lymphocyte culture was also inhibited by anti-Lyt-2, but not affected by anti-Lyt-1 or anti-Thy-1 antibodies. Although Lyt-1+ lymphocytes were required in the mixed lymphocyte reaction as helper cells for proliferation of Lyt-2+ lymphocytes, their helper function was not affected by the presence of Lyt-1 antibodies. Thus, although anti-Lyt-1, anti-Lyt-2 and anti-Thy-1 were of the same gamma 2A immunoglobulin class, had high titers, and interacted with T cells to the same extent, only anti-Lyt-2 blocked T cell functions. Polyclonal activation of T lymphocytes by concanavalin A, in contrast to activation by alloantigens, was not inhibited by Lyt-2 antibodies, suggesting that Lyt-2 antibodies interfere with T cell function at the level of the T cell antigen-receptor. The role which Lyt-2 molecules may play in T cell function is discussed.

Capacity of human oral leucocytes to mediate antibody-dependent cell-mediated cytotoxicity

The ability of human oral leucocytes to mediate antibody-dependent cell-mediated cytotoxicity (ADCC) was studied using a 51chromium ( 51Cr)-release assay. Oral leucocyte or peripheral blood leucocyte effector cells were reacted with antiserum-treated 51Cr-labelled murine lymphoma target cells and 51Cr release was measured. Morphologically-comparable, neutrophil-rich leucocyte populations from either peripheral blood or the mouth were capable of mediating ADCC, the difference in capacity of the 2 groups being reflected by the amount of lysis seen at different effector cell:target cell ratios. The ADCC mediating property of leucocytes may help to explain immune injury in oral tissue.

Natural Cell-Mediated Immunity to Lymphoma Cells. I. Characteristics of Effector Cells in a Cytostasis Assay in Vitro2

Spleen cells from normal, nonimmune, CBA or (CBA X AKR)F1 mice markedly and rapidly inhibited the incorporation of [3H]thymidine by two different T-cell lymphomas in an in vitro cytostasis assay. These were the I-529 lymphoma of spontaneous AKR origin and the Moloney murine leukemia virus-induced YAC lymphoma of A mouse origin. Spleen cells were the most efficient inhibitors for both types of target cells, whereas lymph node cells were much less active and thymus cells showed little or no activity. Granulocytes, as well as conventional T- and B-lymphocytes, were excluded as important contributors to the cytostatic cell population. Spleen cells were separated on nylon wool, Sephadex G-10 columns, or plastic petri dishes and tested for activity in the cytostasis assay or for cytotoxicity against 51Cr-labeled lymphoma target cells. Adherent cells carried almost all cytostatic activity against the AKR lymphoma but also showed significant cytotoxic activity against these target cells. In addition, the cytostatic activity against the YAC lymphoma was mainly due to adherent spleen cells, but nonadherent cells were relatively more active against this target than against I-529 cells. Such nonadherent spleen cells further showed increased cytotoxic activity, compared to the whole spleen cell population.

Non-specific cytotoxicity of spleen cells in mice bearing transplanted chemically induced fibrosarcomas

Spleen cells collected from mice bearing transplanted chemically induced syngeneic fibrosarcomas non-specifically inhibited DNA synthesis of sarcoma and lymphoma target cells in vitro. Splenocytes from mice hyper-immunized against a syngeneic sarcoma specifically inhibited DNA synthesis of the tumour used for immunization. The impairment of tumour-cell DNA synthesis was associated in vitro with cytostasis, and lysis of the target cells was not seen. Since treatment with anti-theta serum and complement did not impair cytostatic action of the spleen cells, and since thymus-deprived animals showed similar activity to normal mice, T lymphocytes were not involved in non-specific cytostasis. Removal of phagocytic adherent cells by carbonyl iron markedly inhibited the cytostatic activity of the spleen cells, suggesting a role in this reaction for cells of the monocyte-macrophage series. The presence of an actively growing sarcoma was a prerequisite for the expression of non-specific cytostasis, since surgical excision resulted in complete disappearance of this activity of spleen cells.

Gross‐virus‐induced lymphoma in the rat. V. Natural cytotoxic cells are non‐t cells

The cytotoxic cells from the spleens of normal rats, which lyse Gross-virus-induced lymphoma target cells in a short-term 51Cr release test, are predominantly small to medium-sized cells sedimenting at 4-5 mm/h as shown by velocity sedimentation analysis. Their cytotoxic activity is relatively resistant to gamma-radiation, 50% surviving 1,000 rads and 30% remaining after 5,000 rads, and to heat, since 20 min incubation at 48-51 degrees C is required for its abolition. In these properties the natural killer (NK) cells are very similar to the cytotoxic T cells from tumour-immune rats, and they share in addition a requirement for Ca++ ions for cytolysis. They differ in that they are non-T cells as defined by their resistance to anti-T-cell antiserum and complement, and by their presence in T-cell-deprived rats. They lack detectable surface Ig, Fc receptors and phagocytic or adherence properties and belong therefore to that small proportion of lymphoid cells lacking the surface markers of T or B lymphocytes, as do the comparable NK cells of mice. Cytotoxicity appears to involve an autonomous, papain-sensitive recognition structure on the surface of NK cells, rather than acquired cytophilic antibody operating through an antibody-dependent mechanism.

Inhibition of human lymphoma cell-line colony formation by lymphocytes from patients with lymphoma and cancer hospital employees.

Inhibition of human lymphoma cell-line colony formation (ICF) was induced by peripheral blood lymphocytes (PBL) from patients with lymphoma and apparently healthy cancer hospital personnel. PBL from patients with non-lymphoma neoplasms and from normal blood bank donors did not elicit ICF. ICF was most marked when PBL were cocultivated for 24 hours in a ratio of 1000:I with target lymphoma cells that had been cultured for 24 hours before exposure. No significant ICF was observed when target cells consisted of human neurogenic sarcoma, melanoma, colon adenocarcinoma, or Chinese hamster cells. It is possible that ICF is elicited by PBL sensitized to a cross-reacting antigen present on the membrane of cultured lymphoma cells. This antigen may be synthesized by a transmissible etiologic factor.

Alteration in DNA synthetic response of thymocytes from NZB mice of different ages.

Thymocytes from NZB and DBA/2 mice were injected into lethally irradiated C57 B1/6 recipients. DNA synthesis in spleen and lymph node was measured as the incorporation of radioactive 5-iodo-2-deoxyuridine. The generation of cytotoxic effector cells was also studied in an in vitro cytotoxicity assay, with EL-4 lymphoma target cells. The kinetics of DNA synthesis were similar for 2- and 8-week-old DBA/2 donors and for 2-week-old NZB donors with a peak on day 4. Thymocytes from 8-week-old and 9-month-old NZB donors showed a delayed onset of DNA synthesis which was still increasing on day 6. When NZB donor thymocytes from 2- and 8-week-old mice were mixed together before injections, as few as 25% of 8-week-old cells gave a DNA synthetic response characteristic of this aged population. These results suggest an abnormal thymocyte development in NZB mice which may relate to the subsequent emergence of autoimmune disease.

Mechanism of immunologically specific killing of tumour cells by macrophages.

THE increase in anti-microbial activity of macrophages which occurs in animals that have been infected with living microorganisms is frequently non-specific1. In contrast, the anti-tumour activity of macrophages from immunized animals has been demonstrated in vitro to be immunologically specific2,3. The experiments to be described may throw light on this paradox. They show that the killing of tumour cells by macrophages is made up of an immunologically specific interaction which is followed by a non-specific lethal reaction. A similar pattern has been described for the bactericidal action of immune macrophages3. We have described three ways of obtaining immunologically specific macrophages cytotoxic to tumour cells3,5. These are (1) from the peritoneal cavity of suitably immunized mice (see later); (2) “arming” in vitro by contact of non-immune macrophages with spleen cells from hyperimmunized mice, and (3) “arming” in vitro by exposure of non-immune macrophages to the cell-free supernatant obtained when spleen cells from immunized mice are cultured with the specific antigen. All such macrophages, on coming into contact with specific antigens, undergo a transformation (referred to as “activation”) which renders them capable of killing. The actual destruction of the target cell following direct contact with the “activated” macrophages is non-specific. Moreover, this non-specific killing may also be demonstrated by macrophages “armed” against tubercle bacilli (BCG) which are “activated” after exposure to the solubilized protein derivative from tubercli bacilli, PPD, and are able to kill tumour cells. In the original experiments3,5 in which target lymphoma cells were added to “armed” macrophages the immunologically specific stage and the non-specific stage of the cytotoxic reactions were not separated and occurred sequentially (Fig. 1).

Studies on allogeneic inhibition II. Inhibition of mouse tumor cell growth by In vitro contact with cells containing foreign H‐2 antigens

AbstractMouse lymphoma cells were inoculated into preirradiated syngeneic hosts after incubation with lymph‐node, spleen, liver or lymphoma cells from different sources in the presence of phytohemagglutinin. Neutralization of tumor growth was detected after incubation of lymphoma target cells with added untreated or X‐irradiated normal lymphoid or liver cells or with X‐irradiated intact or ultrasonically disintegrated lymphoma cells in all cases where the added cells contained H‐2 isoantigens which were foreign to the targets.