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PubMed1985

Modulation of human blood lymphocyte cytotoxicity by the phorbol ester tumor promoter P(Bu)2: increase of target binding, impairment of effector recycling, and activation of lytic potential which is independent of IL-2.

Treatment of lymphocytes with the tumor promotor P(Bu)2 enhanced their target-binding capacity. In the conventional 51Cr-release assay, the cytotoxic potential of lymphocytes pretreated with P(Bu)2 for a short time was reduced while after prolonged treatment their function was increased. The peak of lytic potential was attained after 15 hr of exposure. Comparison of the cytotoxic results obtained in suspension and immobilized conjugate assays suggested that P(Bu)2 treatment causes an impairment of the recycling capacity of lymphocytes. After prolonged exposure, the lytic machinery became activated as reflected by the reduced time elapsing after contact between effectors and targets and the delivery of lethal hit. The activation was also observed in the immobilized agarose assay. It was reflected by the elevated proportion of damaged targets that were bound to the treated lymphocytes. The P(Bu)2- and interferon-induced augmentation of lytic potential is achieved through different mechanisms. Combination treatment applied to the effectors in sequence (first P(Bu)2 followed by interferon), resulted in an additive effect. Similarly, simultaneous treatment with IL-2 and P(Bu)2 also gave an additive increase in cytotoxicity. Addition of antibodies directed against IL-2 did not abrogate the P(Bu)2 effect. Consequently, neither interferon nor IL-2 are involved in the phorbol ester-induced cytotoxic function.

Animals↗
PubMed1985

Heterogeneity of human natural killer recognition demonstrated by cloned effector cells and differential blocking of cytotoxicity with monoclonal antibodies.

Monoclonal antibodies (MoAb) against cell surface determinants were employed to investigate the specificity of natural killer (NK)-like lysis by cloned human effector cells recognizing only K562, only HSB2, or both K562 and HSB2 target cells. MoAb W6/32.HL, TU39, YD1/48.HLK, and anti-Tac failed to inhibit lysis despite the expression of antigens bound by these MoAb on the effector cell surface. MoAb OKT3 moderately (less than or equal to 50%) blocked lysis of K562 and HSB2 targets, whereas MoAb 13.1, which binds T200 molecules, strongly (up to 95%) blocked lysis of K562, but not HSB2, targets. MoAb 13.1 inhibited lysis by clones which killed only K562, as well as lysis by those which killed both HSB2 and K562. In the latter case, however, only lysis of K562 was inhibited. Taken together, these results may suggest the existence of multiple receptor specificities on a single NK-active clone.

Antibodies, Monoclonal↗
PubMed1985

Characterization of immune effector cells present in early murine decidua.

It has been suggested that murine decidual cells act as an important immunoregulatory population localized to the pregnant uterus. We have examined early murine decidua to determine if immune effector cells occur in the decidual environment in proximity to the conceptus. High levels of natural killer (NK) cell activity were found consistently in decidual cell suspensions with peak activity occurring on Day 6.5 of gestation. NK activity declined as pregnancy proceeded and was not significant by Day 12.5 of gestation. Decidual cell suspensions did not appear to contain significant numbers of functional B or T effector cells. No antipaternal T-cell response could be demonstrated even in the decidua of immune mice. Lack of T-cell responses was attributed to the absence of T cells from decidua rather than to their inactivation because precursors of cytotoxic T lymphocytes (pCTL) could not be detected in decidual cell suspensions. Furthermore, the levels of pCTL detectable in spleen cell suspensions could not be reduced by mixing spleen cells with 7.5-day decidual cells. These results suggest that B cells and T cells may not occur in early decidua while NK cells are present and regulated independently.

Animals↗
PubMed1985

The generation of effector T cells in influenza A-infected, cyclosporine A-treated mice.

Specific effector T cells that mediate DTH to influenza virus were found to be formed in vivo in CsA-treated mice. The activity of these cells could only be measured when they were transferred into untreated naive mice. The cells mediating DTH were H-2 restricted in the I region of the MHC. When effector T cells that mediated DTH were transferred into CsA-treated recipients, no DTH activity could be detected. Influenza-specific cytotoxic T cells could not be detected in the spleens of CsA-treated mice given virus intravenously, even when drug treatment was started 3 days after virus administration. There was only a partial restoration of cytotoxic activity when spleen cells from CsA-treated infected mice were cultured in the presence of virus-infected stimulators. This seemed to indicate that Class I-restricted responses were more susceptible to CsA than the generation of Class II (or I-region-restricted) responses.

Animals↗
PubMed1986

Allogeneic responses of human fetal (22- to 25-week) peripheral blood lymphocytes: preferential recruitment of cytotoxic effector cells with both CTL activity and NK-like function.

In the present study, we have characterized human cytotoxic effector lymphocytes generated following in vitro immunization of normal fetal (22- to 25-week) peripheral blood mononuclear cells (FPBMC) by an allogeneic Epstein-Barr virus-transformed B-cell line termed LAZ388. Primary stimulations led to strong FPBMC proliferation. However, subsequent addition of LAZ388 cells to the cultures on Day 8 did not trigger conventional secondary responses. In fact, further proliferation of activated FPBMC required the addition of exogeneous interleukin 2. Cytotoxic activity generated in the mixed-lymphocyte reactions was assayed against LAZ388 immunizing cells as well as against the highly susceptible natural killer (NK) target cell line K562. Eight days after stimulation by LAZ388, there was no specific lysis and a moderate NK-like activity. However, following second and subsequent stimulations a strong killing was measured against both LAZ388 and K562 cells. Blocking experiments performed with relevant monoclonal antibodies suggested that cytotoxicity against immunizing cells was conventionally directed at MHC gene products. Effector cells were further studied using cloning procedures; it was found that all cloned cell lines able to kill LAZ388 cells were also strongly active against K562. Both types of cytotoxic function appeared to be mediated via surface receptors physically or at least functionally associated with T3 proteins.

B-Lymphocytes↗
PubMed1987

Ferritin selectively suppresses delayed-type hypersensitivity responses at induction or effector phase.

The effect of ferritin on the delayed-type hypersensitivity (DTH) response and Arthus-type reaction as assessed by footpad reaction using methylated human serum albumin, human serum albumin, or sheep red blood cells as antigens was investigated. Intraperitoneally administered ferritin was short acting and suppressed either induction or expression of DTH depending on the time of ferritin injection although it did not inhibit the antibody-mediated inflammatory response, the Arthus reaction. Investigation of ferritin's effect on the primary antibody response revealed that the number of IgG plaque-forming cells (PFC) was moderately decreased but IgM PFC were not. These results indicate that the afferent limb, ferritin selectively suppresses antigen presentation and/or clonal expansion of effector cells of cell-mediated immunity, but not that of the antibody response. Antigen presentation by Ia-positive cells and/or lymphokine-responsive inflammatory mononuclear cells at the efferent limb of DTH is suggested to be affected by ferritin. This conclusion is based upon the observations of successful TDTH effector cell transfer from sensitized but ferritin-treated donors and of successful reversal of ferritin-induced suppression of expression of DTH by supplementing normal bone marrow-derived cells containing Ia-positive ones. Thus our in vivo experimental system might be useful for the differential analysis of immunopathological lesions such as a T-cell-mediated, monocyte-dependent and an antibody-mediated inflammatory lesions.

Animals↗
PubMed1989

The molecular basis of granuloma formation in schistosomiasis. IV. T cell-derived suppressor-inducer and suppressor-effector factor reactivities are regulated by a TCR beta chain analog.

In Schistosomiasis mansoni, granulomatous modulation is mediated by antigenically and genetically restricted T suppressor-inducer and suppressor-effector cells and the soluble factors which they produce. The T suppressor-inducer factor (TsiF) is produced by an L3T4+, 14-30+ T cell. TsiF does not suppress directly, but induces the production of T-cell-derived suppressor-effector factor (TseF). TseF directly suppresses granuloma formation in vitro and in vivo. This study describes the molecular properties of TsiF. The factor is a nonimmunoglobulin heterodimer which can be separated into two component chains by dithiothreitol (DTT) reduction. The alpha chain imparts antigenic specificity and bears both the AgR and the epitope recognized by mAb 14-30 which characterizes T cells and factors of the Tsi phenotype. The beta chain imparts genetic restriction and bears both the I-J phenotypic marker and a T-cell receptor for Ag (TCR) V beta 8 determinant. These two chains can complement each other in vitro to reconstitute functional activity. The beta chain also determines the functional activity of T cell-derived suppressor factor (TsF). A beta chain, derived from TsiF, can complement the alpha chain derived from TsiF or TseF to reconstitute TsiF, but not TseF functional activity. Conversely the beta chain of TseF can reconstitute only TseF activity. These findings suggest that TsiF bears structural homologies to the TCR borne by Tsi cells and that the beta chain mediates the mode of functional interactions between TsFs and their target cells.

Animals↗
PubMed1989

Biological response modifier as antigen: OK432-specific T-cell clone as an anti-tumor effector cell.

OK432, a Streptococcus preparation, is a biological response modifier that has been used in the treatment of malignant diseases. A cloned Thy 1.2+, L3T4+, Lyt 2.2- T cell (OK2.21), specific for OK432 and restricted to I-Ed, was isolated from BALB/c mice immunized with OK432. OK2.21 not only secreted interleukin 2 but also killed Iad-bearing B-lymphoma cells in an antigen-specific manner. The clone also killed Ia-negative bystander tumor targets, but only in the presence of both OK432 and antigen-presenting cells. Despite the cytotoxicity against tumor cells, OK2.21 did not kill OK432-pulsed normal spleen cells. Injection of this clone together with OK432 to tumor-bearing BALB/c mice prolonged their survival, suggesting that this clone acts as an anti-tumor effector (or effector-inducer) cell in the therapy with OK432.

Animals↗
PubMed1990

Demonstration of a splenic cytotoxic effector cell in mice of genotype SCID/SCID.BG/BG.

Splenocytes from mice of genotype scid/scid.bg/bg were tested in vitro to characterize the nature of the immunological deficit in these doubly mutant animals. The cells were unresponsive to the mitogens LPS and Con A and to alloantigens, as predicted for scid/scid genotype. Splenocytes from scid/scid.bg/bg lysed the NK cell-sensitive target cell line YAC at levels approximately 50% lower than those observed for scid/scid splenocytes. Splenocytes from SCID-beige mice failed to lyse the NK-resistant, LAK-sensitive cell line P815 but showed high levels of activity against the murine placental cell line Be6. Lytic activity was found in both nonadherent and plastic adherent cells and was eliminated by pretreatment of the effectors with anti-asialo-GM1 and complement. Incubation of 1 x 10(5) splenocytes with hrIL-2 failed to induce blastogenesis in scid/scid.bg/bg cells but produced a response in cultures of scid/scid or bg/bg spleen cells. However, blastogenesis and elevated levels of LAK-type killing were observed following incubation of higher numbers of scid/scid.bg/bg splenocytes in hrIL-2. Thus, doubly mutant scid/scid.bg/bg mice have reduced NK cell activity, in comparison to scid/scid mice, and appear to possess LAK-like effector cells and LAK cell precursors.

Animals↗
PubMed1990

Immunosuppressive activity of staphylococcal enterotoxin B. II. Activation of suppressor-effector cells by a staphylococcal enterotoxin B-induced suppressor factor.

The capacity of staphylococcal enterotoxins to stimulate all T cells bearing certain T cell receptors has recently generated a great deal of interest. These toxins are believed to bind directly both to the TCR:CD4 complex via its V beta domains and to class II MHC molecules on accessory cells prior to T cell activation. Previous studies from this laboratory have demonstrated that staphylococcal enterotoxin B (SEB) is capable of inducing multiple T suppressor cell populations which can inhibit in vitro antibody responses. Additional studies have demonstrated that the suppressive activity of these cells is mediated, at least in part, by an I-J-restricted suppressor factor. Efforts to characterize the inhibitory activity of this factor have demonstrated that the suppressive element is capable of activating both early and late acting suppressor cell populations in vitro. Analysis by both positive and negative selection shows that cells bearing the Lyt1-2+ surface marker phenotype are active early, whereas Lyt1+2+ cells are active both early and late in the antibody response. Additional experiments using various strains of mice as sources of suppressor factor and of naive splenocyte populations have demonstrated that activation of suppressor-effector cells by this suppressor factor is restricted at the I-J, but not Igh, gene locus. These studies suggest that this SEB-induced suppressor factor alone provides the signals necessary for the induction and activation of suppressor-effector cell activity.

Animals↗
PubMed1991

Effector phenotypes and mechanisms of antitumor immune reactivity of tumor-immunized and tumor-bearing mice in two syngeneic tumors.

By using two different syngeneic tumors, Meth A sarcoma and RL male 1 lymphoma of BALB/c origin, the present study was designed to investigate the subset(s) of T cells mediating in vivo antitumor immune responses and some of the effector mechanisms of in vivo protective immunity in BALB/c mice immunized against tumor or bearing tumor. Spleen cells from the mice immunized against Meth A tumor or bearing Meth A tumor inhibited the growth of Meth A tumor in the Winn assay. In the Meth A-immunized mice, L3T4+ (CD4+) cells played a major role in mediating the inhibitory activity against Meth A tumor growth, whereas in the Meth A-bearing mice, the antitumor protective immunity was mediated by both L3T4+ and Lyt-2+ (CD8+) cells. Spleen cells from the Meth A-immunized or Meth A-bearing mice were not able to generate cytotoxic T lymphocytes (CTL) directed against Meth A tumor after the in vitro restimulation of spleen cells with mitomycin C (MMC)-treated Meth A cells, while fresh spleen cells from the Meth A-immunized or Meth A-bearing mice were able to induce the strong delayed-type hypersensitivity (DTH) responses to Meth A tumor. The DTH response to Meth A tumor was mediated by L3T4+ cells in the Meth A-immunized mice and by both L3T4+ and Lyt-2+ cells in the Meth A-bearing mice. In the similar experiments performed in the RL male 1 lymphoma, the antitumor activity in spleen cells from the RL male 1-immunized or RL male 1-bearing mice depended on Lyt-2+ but not L3T4+ cells in the Winn assay. When spleen cells from the RL male 1-immunized or RL male 1-bearing mice were cultured with MMC-treated RL male 1 cells for 5 days, an appreciable CTL response to RL male 1 tumor was induced. These results suggest that the nature of tumor and/or tumor antigens determines which T cell subset is required to exhibit the protective immunity against tumor and thus the different effector mechanisms could be induced in the different tumor models. Furthermore, these data support the conclusion that antitumor T cell responses are affected by the immune state of host to tumor.

Animals↗
PubMed1991

Anti-CD3 antibody-induced activated killer cells: cytokines as the additional signals for activation of killer cells in effector phase to mediate slow lysis.

This study examines the role of cytokines in activating the effector cells to mediate slow lysis. After activation of splenocytes by alpha CD3, further culturing the cells in the absence of alpha CD3 resulted in the generation of activated killer cells (CD3-AK-) to mediate slow lysis. In contrast to fast lysis which was not affected by a PKC inhibitor H-7, slow lysis was inhibited. These findings suggested that a PKC-dependent activation phase preceded the lytic phase in slow lysis. To explore the mechanism for activating the lytic machinery in slow lysis, we examined the roles of cytokines in these reactions. First, it was found that alpha IL-2 or an alpha IL-2/alpha IL-4 combination inhibited slow lysis but had no effect on fast lysis. Secondly, IL-2, IL-4, or TNF alpha converted a noncytolytic CD3-AK- cells to mediate slow lysis, but they did not augment fast lysis. IL-2 and IL-4 had additive effect, and TNF alpha synergized with IL-2 to further augment the CD3-AK- cytolytic activity. Exogenous IL-6 and INF did not have any appreciable effect on the cytolytic activity of the killer cells. Besides TNF alpha, these cytokines were not directly cytotoxic to the target cells, indicating that they were not cytotoxic factors per se. Treatment with cycloheximide for 24 hr abrogated the cytolytic activities of CD3-AK cells, suggesting that a cytotoxic factor(s) was continuously synthesized to be stored in activated killer cells and was catabolized within 24 hr. Our results indicated that in the effector phase of slow lysis, after activating the CD3-AK- cells by the first signal (appropriate target cells), IL-2 and/or IL-4 appeared to be the second signal to initiate a cascade of events which triggered the release of other cytokines (e.g., TNF). This process resembles the secondary (memory) type of immune response. These events lead to full activation of the killer cells and converted the preformed cytotoxic factors into active form to initiate the lytic reaction and completed the lytic process.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1991

Characterization of effector functions of v-raf/mil- and v-myc-transformed murine splenic macrophage cell lines.

We have characterized several of the cytocidal effector functions of a series of cell lines derived by recombinant retroviral transformation of individual clones of C3H/HeJ mouse splenic macrophages. The three cell lines described in this report (4.01, 4.07, 4.14) all expressed equivalent tumoricidal activity against P815 tumor target cells. However they differed in their high avidity binding of tumor cells (4.01 = 4.14 greater than 4.07), as well as in the killing of Leishmania major (4.01 = 4.07 greater than 4.14), the expression of antibody-dependent cellular cytotoxicity against chicken erythrocytes (4.14 greater than 4.01 greater than 4.07), and finally, in the tumor-stimulated release of tumor necrosis factor-alpha (4.01 = 4.14 greater than 4.07). The stable and restricted expression of distinct effector functions among these three cell lines makes them particularly valuable as models for establishing the precise mechanisms by which cytocidal functions are effected. In addition, they should also prove of value in understanding the basis for macrophage functional diversity.

Animals↗
PubMed1992

Evidence for involvement of TNF-alpha in the induction phase and IFN-beta in the effector phase of antiproliferative activity of splenic macrophages.

Splenic macrophages play a key role in regulating cell proliferation during a variety of chronic perturbations of the hematopoietic system. This regulatory activity is in sharp contrast to the activities of inflammatory monocytes/macrophages in that it is not dominated by the secretion of prostaglandins or toxic metabolites such as peroxides. A productive model for studying these nontoxic regulatory activities of splenic macrophages has been provided by macrophages generated in vitro (M phi-c) during autologous spleen cell culture. The M phi-c effectively inhibit (greater than 90%) lymphocyte proliferation by inhibiting G1----S phase progression without inhibiting the production of interleukins by the lymphocytes. Conditioned medium from M phi-c activated with LPS + rIFN-gamma effected a similar G1 arrest of activated lymphocytes. The involvement of IFN-beta in effecting the antiproliferative activity is suggested by (1) the ability of monospecific anti-IFN-beta mAB, but not anti-TGF-beta, anti-IL-1, anti-TNF-alpha, or anti-IFN-gamma, to neutralize the antiproliferative activity in the M phi-c supernatants and (2) the ability of purified IFN-beta to effect a similar inhibition of cell proliferation (i.e., G1 arrest without inhibition of interleukin production). rTNF-alpha and rIFN-gamma could not effect such an inhibition of cell proliferation and did not synergize with IFN-beta in producing such an antiproliferative effect. The M phi-c could be activated to effector function by a combination of LPS + rIFN-gamma or rTNF-alpha + rIFN-gamma, but not by any one of those reagents alone. LPS alone was sufficient to stimulate TNF-alpha production by the M phi-c. Activation of the M phi-c by LPS + rIFN-gamma could be completely blocked by anti-TNF-alpha antibodies. These data suggest that the M phi-c can be induced to produce inhibitory levels of cytostatic cytokines by a TNF-alpha autocrine loop that is IFN-gamma dependent. The in vivo relevance of this effector mechanism is suggested by, and discussed in the context of, the recent reports of "spontaneous" production of IFN-beta during immunological disorders.

Animals↗
PubMed1985

Colony morphology on agar is a sensitive indicator for growth effectors.

Colonies of Chinese hamster ovary (CHO) cells growing on agar exhibit changes in colony morphology and size in response to extremely low doses of hormones and growth factors. Computer-aided densitometric scanning of photographs of these colonies allows the quantitative measurement of these morphological changes. Correlation of these changes with dosage for a variety of growth effectors is a sensitive assay for the effects of these factors, both alone and in combination, and should be useful in comparing effects of agents with similar biological activities and in the search for variant cell types with altered responsiveness. Cells growing attached to solid substrates are often responsive to these low dosages and do not seem to mimic in vivo growth effector phenomena as well as colonies growing in three dimensions on agar.

Animals↗
PubMed1985

Purification and characterization of two vascular endothelium effectors from fetal bovine retina, vitreous and serum.

The purification and characterization of uridine and thymidine, two previously isolated vascular endothelium effectors, are described. These two effectors were purified from all dialyzable fractions of fetal bovine serum (FBS), vitreous, and retina. The present study demonstrates the stimulatory characteristic of uridine and thymidine on the proliferation of aortic endothelial cells. The stimulation appears to link to their utilization by the cells in a dialyzed FBS-dependent manner. In the presence of optimal concentrations of uridine (10 microM), thymidine (0.8 microM), and dialyzed FBS (3 mg ml-1), a markedly enhanced vascular endothelial cell proliferation is attainable; uridine and thymidine alone had no significant stimulatory effect. The presence of both nucleosides, however, increased the concentration of dialyzed FBS required for half-maximum proliferation activity of fetal bovine aortic endothelial cells and also increased maximum activity. Studies with fetal bovine aortic endothelial cells showed that the activity of uridine kinase in the cells was activated by dialyzed FBS, but not by uridine and thymidine. Uridine and thymidine exerted no marked stimulatory effect on Balb/c 3T3, Swiss 3T3, and SV-T2 as noted with endothelial cells. The significance of the present findings to the proliferation of vascular endothelial cells in the retina is discussed.

Animals↗
PubMed1983

Autophosphorylation of type 2 casein kinase TS at both its alpha- and beta-subunits. Influence of different effectors.

Rat liver casein kinase TS (Ck-TS) having quaternary structure alpha 2 beta 2, autophosphorylates at its 25 kDa, beta-subunits, incorporating up to 1.2 mol P/mol enzyme. According to their effects on the autophosphorylation pattern the effectors of Ck-TS activity can be grouped into 3 classes: (i) inhibitors, like heparin, which also prevent the autophosphorylation of the beta-subunit; (ii) stimulators possessing several amino groups (like spermine) which increase the autophosphorylation at the beta-subunit; (iii) stimulators possessing several guanido groups, like protamines and related peptides, which prevent the phosphorylation of the beta-subunit, while promoting the autophosphorylation of the 38 kDa alpha-subunit. In the presence of such polyarginyl effectors the 130 kDa Ck-TS is converted into forms with higher sedimentation coefficient.

Animals↗
PubMed1989

Receptor and effector interactions of Gs. Functional studies with antibodies to the alpha s carboxyl-terminal decapeptide.

Antibodies generated to a synthetic decapeptide, RMHLRQYELL, representing the carboxyl-terminus of Gs-alpha have been characterized in immunoblots and functional studies. This antibody, designated RM, reacts exclusively with a doublet of proteins of 52 and 45 kDa in immunoblots of bovine brain and wild-type S49 murine lymphoma cell membranes. No such reactivity is seen in membranes from cyc- S49 cells, which lack Gs. RM blocks receptor-mediated activation of Gs and adenylyl cyclase in membranes from wild-type S49 cells. RM could also immunoprecipitate adenylyl cyclase activity in detergent extracts from GTP[gamma]S- or fluoride-preactivated bovine brain membranes; thus binding of alpha s to effector and carboxyl-terminal antibody was mutually compatible. Such experiments provide an approach for the elucidation of functionally relevant interactions of G-proteins with receptors and effectors in the membrane.

Adenylyl Cyclases↗