Human Lymphocyte-mediated Cytotoxicity Research Articles

The Effect of Bryostatin 1 on Human Lymphocyte-Mediated Cytotoxicity

We compared the effects of bryostatin 1 (BRYO), a non-tumor-promoting protein kinase C activator, and phorbol myristate acetate (PMA) on various types of lymphocyte cytotoxicity. An 18-h preincubation of lymphocytes with 10(-8) M BRYO inhibited natural killer (NK) activity but this inhibition was not statistically significant (p = 0.28). In contrast, NK activity was significantly enhanced by preincubation of lymphocytes with 10(-8) M PMA (p = 0.0012). Thus, in 13 experiments, the mean LU/10(6) was 21 +/- 12 for control cultured cells, 16 +/- 14 for BRYO cultured cells, and 40 +/- 22 for PMA cultured cells as determined in 51Cr-release assays with K562 target cells. Both BRYO and PMA inhibited lymphocyte antibody-dependent cell-mediated cytotoxicity (ADCC) such that, at a 20:1 effector-to-target ratio, control lymphocytes had a mean 49 +/- 12% specific 51Cr release of antibody-coated target cells while BRYO and PMA cultured lymphocytes had 12 +/- 6 and 8 +/- 12%, respectively, in four experiments. The reduction in ADCC was paralleled by a decrease in Fc receptor (CD16) expression as determined by immunofluorescence analysis. We assessed the ability of BRYO and PMA to induce lymphokine-activated killer (LAK) activity by culturing lymphocytes with optimally mitogenic doses of these compounds and testing for cytotoxicity of Daudi target cells. While both BRYO and PMA induced [3H]thymidine uptake, neither induced LAK activity. Furthermore, both compounds inhibited induction of LAK activity by recombinant interleukin-2 (rIL-2) in cocultures. We also analyzed the effect of BRYO and PMA on preactivated LAK effector cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytotoxic and immunostimulatory effects of Bacteroides cell products

The etiologic role of Bacteroides in both periodontal and periapical infections has been well documented, with current interest focusing on the specific pathogenic mechanisms involved. The effects of cell fractions derived from Bacteroides gingivalis (BG), Bacteroides intermedius (BI), and Bacteroides asaccharolyticus (BA) have been studied in vitro through: an assessment of the direct cytotoxic effects on human gingival fibroblasts using a tetrazolium dye reduction assay, an evaluation of murine lymphocyte stimulation and interleukin-1 release, and the induction of human lymphocyte-mediated cytotoxicity. Both BG and BI stimulated interleukin-1 release (P less than 0.001), while BA, a nonoral organism, was not significantly active in this respect. Only BG sonicates were able to induce lymphocyte-mediated cytotoxicity (P less than 0.005). All three Bacteroides species demonstrated direct cytotoxic effects on cultured gingival fibroblasts, and these effects were related to the relative protein content and endotoxin activity of the sonicate preparations for each organism. These data show that BG and BI possess factors which may enhance their virulence through activities not shared with BA.

Nonspecific human lymphocyte-mediated cytotoxicity induced by immobilized IgG aggregate

Normal human lymphocytes were induced to lyse nonsensitized erythrocytes when concomitantly incubated on immobilized IgG aggregate with various erythrocyte target cells. These included ox, sheep, chicken, and human red blood cells. Only immobilized aggregate would initiate cytolysis. The IgG aggregate was prepared from normal, healthy adult donors and did not possess target cell specificity (e.g., human erythrocyte lysis was initiated by autologous IgG). Normal human lymphocytes could be induced to lyse the red blood cell targets only after a preincubation with adherent mononuclear cells; however, freshly prepared lymphocytes depleted of IgG-FcR − cells were cytolytic. Cytolysis induced by immobilized IgG-aggregate can be distinguished from NCMC and ADCC by its requirement for immobilized IgG aggregate and the absence of target cell specificity in the IgG-aggregate preparation.

Spontaneous human lymphocyte-mediated cytotoxicity against tumor target cells: VII. The effect of immunodeficiency disease

Spontaneous lymphocyte-mediated cytotoxicity (SLMC) and antibody-dependent cellular cytotoxicity (ADCC) was assessed in 13 patients with immunodeficiency diseases—immunodeficiency-thymoma syndrome (1), Bruton type agammaglobulinemia (3), and common variable hypogammaglobulinemia (9). SLMC and ADCC function were intact (and possibly enhanced) in the patient with immunodeficiency thymoma. Both ADCC and SLMC were detectable in the three patients with X-linked agammaglobulinemia, one of whom had lower than expected SLMC. In all of the immunodeficient patients, the relative inability of B lymphocytes to produce immunoglobulin in vivo or in vitro did not consistently affect the ability of (presumably) other lymphocytes to mediate SLMC and ADCC, although in three of the CVH patients this was lower than normal. In every case, removal of Fc receptor-bearing cells from the patients' lymphocyte preparations severely depleted SLMC (and ADCC when tested), but cytotoxicity was either unchanged or enhanced by depletion of E rosette forming T cells. The effects of Fc receptor-positive cell depletion, T-cell depletion, culture serum variation, or the addition of antibody-coated erythrocytes to the assay were similar on both SLMC and ADCC effector cells (“NK” and “K” cells), and whether patients' or normal lymphocytes were tested. The possible significance of the results with respect to surveillance against cancer is discussed.

Spontaneous human lymphocyte-mediated cytotoxicity against tumor target cells-III: Stimulatory and inhibitory effects of ionizing radiation

Human peripheral blood contains cells which are cytotoxic in vitro for certain types of malignant cells, even though the donors have had no known exposure to cancer of any type. The identity of these cytotoxic cells is a matter of controversy since they do not fit readily into any commonly recognized category of peripheral blood cell. In this paper, we present a radiobiological characterization of these cells. The radiation survival curve for the spontaneous cytotoxic function had a D o0 of approximately 750–850 rad and a broad but variable shoulder. The possibility that spurious D o values were obtained as a result of radiation-induced interphase death of the cytotoxic cells was examined experimentally. Moderate doses of radiation caused definite enhancement of cytotoxicity. Evidence was obtained for the existence of ralatively radiosensitive cell interactions which existence of relatively radiosensitive cell interactions which ordinarily result in a decrease in cytotoxic efficiency and which may be responsible for the observed stimulatory effect of irradiation. This parameter of the survival curve does not appear to be a consequence of intrinsic radiobiological properties of the cytotoxic cells. The Fc receptor function (the ability of the cells to bind antigen :IgG complexes via the Fc portion of the IgG molecules) appears to be relatively radioresistent.

Spontaneous human lymphocyte-mediated cytotoxicity against tumor target cells: IV. The suppressive effect of normal pregnancy

The effects of pregnancy and other donor characteristics on spontaneous lymphocyte-mediated cytotoxicity (SLMC) were studied. Sex, age, and stage of the menstrual cycle had no significant effect on the SLMC of the control donors, the SLMC was significantly lower in pregnant donors in the second or third trimester. However, this lowered level of activity was still within the 95 per cent confidence limits of the normal population and parity had no cumulative effect. At delivery, fetal cord blood lymphocytes possessed substantial cytotoxic activity, further evidence that the fetus is immunologically competent at birth. The relevance of these data to the immunologic coexistence of the mother and fetus is discussed.

Suppression of human cytotoxic lymphocytes by methylprednisolone. An immunosuppressive mechanism of action of steroids.

In order to gain insight into the immunosuppresive mechanism of action of corticosteroids, an in vitro model of the cellular immune response was used to study the effect of methylprednisolone on human lymphocyte-mediated cytotoxicity. Concentrations from 0.25 to 10 microgram/ml were equally effective in producing 74% suppression lymphocyte-mediated cytotoxicity when the steroid was present during the entire period of in vitro sensitization. A 12.5-fold increase in effector to target cell ratio was required to achieve 30% 51Cr release when cytotoxic lymphocytes were generated in the prescence of methylprednisolone. Lymphocyte-mediated cytotoxicity was suppressed 48% when methylprednisolone was present only during the initial 24 hr of the 7-day in vitro sensitization period. Methylprednisolone also effectively inhibited cytotoxicity when it was incubated with sensitized lymphocytes for 3hr before incubating these cells with target cells. Our observations suggest that two of the major immunosuppressive mechanisms of action methylprednisolone are suppression of the generation of cytotoxic lymphocytes and suppression of specifically sensitized cytotoxic lymphocytes.

Spontaneous human lymphocyte-mediated cytotoxicity against tumor target cells

Spontaneous human lymphocyte-mediated cytotoxicity against tumor target cells

Spontaneous human lymphocyte-mediated cytotoxicity againts tumour target cells. I. The effect of malignant disease.

Spontaneous human lymphocyte-mediated cytotoxicity (SLMC) against tumour-cell targets was examined in a series of patients with localized or malignant disease, both treated and untreated, and patients with untreated chronic lymphocytic leukemia (CLL). The level of SLMC was assessed by means of two previously established assay systems; the xenogeneic assay involving the mouse mastocytoma line P815, and the allogeneic assay in which the human chronic myelogenous leukemia-derived line, K562, was used. The assay systems involve the use of Ficoll-Isopaque-separated, iron-plus-magnetism-purified lymphocytes in an overnight 51chromium release assay, and reflect the cytotoxic ability of human non-T, complement receptor-, Fc receptor-positive lymphocytes. In the present paper, lymphocytes from all normal donors tested showed significant activity in the SLMC assay, with some variation from day to day. This variation was markedly reduced when different normal donors were tested on the same day and under identical experimental conditions. In contrast, lymphocytes from many patients with malignant disease had decreased SLM activity, and this decrease was highly significant in patients with treated or untreated metastatic disease, or untreated CLL. This was also the case when the data were expressed relative to the number of cytotoxic cells in the normal control population, or in comparison to the relative SLMC activity of lymphocytes from patients with other conditions. Markedly decreased SLMC was observed in some patients in spite of normal T and B lymphocyte proportions, or the presence of the ability to mount a vigorous delayed hypersensitivity reaction to PPD. A comparison of the xenogeneic and allogeneic assays showed that the same information with respect to whether SLMC was normal or abnormal was obtained with both assays in the majority of cases. The significance of the data is discussed with respect to the possible role of SLMC in vivo and the relevance of SLMC to the assessment of specific cell-mediated cytotoxicity in malignant disease.

Inhibition of antibody-dependent human lymphocyte-mediated cytotoxicity by immunoglobulin classes, IgG subclasses, and IgG fragments.

The cytotoxicity of human peripheral blood lymphocytes against chicken erythrocytes sensitized by rabbit antibodies was inhibited by human immunoglobulin and immunoglobulin fragments. Myeloma proteins isolated in dimeric state or aggregated by heat treatment inhibited better than the corresponding monomeric proteins. Strong inhibition was observed with IgG1 and IgG3, and with IgG2 after aggregation, while IgG4 inhibited very little. No inhibition was found with IgM, IgA. IgD and IgE. The F(ab')2. and Fab fragments of IgG inhibited poorly or not at all. While‐ considerable inhibition was observed with the Fc fragment, the pFc’ fragment, which roughly corresponds to the C‐terminal half of the Fc portion, showed little inhibitory capacity. A fragment isolated from IgG3, containing an extension of the N‐terminal part of Fc (the Fch fragment), was an even better inhibitor than tin Fc fragment. The inhibitory capacity of the Fch and Fc fragments was greatly diminished following partial reduction and alkylation On the basis of the inhibitory pattern of IgG fragments, it is suggested that the region on the immunoglobulin molecule involved in binding to the Fc receptor of the effector lymphocytic cell may be located within the CH2 domain.