Influence of interleukin-2 on the differentiation of macrophages

Macrophage precursor cells, enriched in the light fraction of murine bone marrow, were cultured in vitro under the influence of CSF-1 or IL-2 or both cytokines. In the presence of CSF-1 or CSF-1 and IL-2 strong proliferation occurred, whereas in the presence of only IL-2 or medium, cells did not proliferate. Thus all proliferating cells had CSF-1 receptors and thus belonged to the macrophage lineage. IL-2 induced in these cells the formation of cytoplasmic granules and concomitantly NK-like lytic activity. Under high dosage IL-2 cells further differentiated into cells containing abundant amounts of cytoplasmic granules and exerted LAK type cytotoxicity. When IL-2 was withdrawn from the culture medium, cells could be redirected to develop the properties of typical macrophages when CSF-1 was present. Thus the composition of the cytokines surrounding macrophage precursors decides on their differentiation pathway.     

Cytolysis of human dendritic cells by autologous lymphokine-activated killer cells: participation of both T cells and NK cells in the killing.

Dendritic cells (DC) play a key role in the initiation of immune response by stimulating the naive T cells. The fate of DC after the initiation of immune response is not clearly understood. Although there are few reports implicating natural killer (NK) cells in the elimination of DC, killing of DC by LAK cells, and specifically by T cells, has not been studied. In this study, we observed that DC, generated from monocytes, in vitro in the presence of granulocyte-macrophage colony-stimulating factor, interleukin-4 (IL-4), and tumor necrosis factor alpha were susceptible to cytolysis by lymphokine-activated killer (LAK) cells induced in the presence of IL-2 and IL-15 but not IL-12 alone. However, LAK cells induced by a combination of IL-12 and suboptimal dose of IL-2 were cytotoxic to DC. When purified lymphocytes were activated with IL-2, the CD8+/CD57- fraction (T-LAK), but not the CD8-/CD57+ fraction (NK-LAK) was cytotoxic to autologous DC. However, when unseparated peripheral blood mononuclear cells were used to generate LAK cells, both T-LAK and NK-LAK fractions showed equal cytotoxicity against autologous DC. Monoclonal antibodies against CD54, CD11a, and CD18 significantly inhibited the cytolysis, indicating that the killing involves the engagement of CD54 with its ligands.     

rIL-4 differentially regulates rIL-2-induced murine NK and LAK killing in CD8+ and CD8- precursor cell subsets

Interleukin 4 (IL-4) and IL-2 have complementary or synergistic roles in many aspects of lymphocyte development. IL-2 supports the induction of cytolytic activity in cytotoxic T lymphocyte (CTL), natural killer (NK), and lymphokine-activated killer (LAK) cells. IL-4 has also been shown to support CTL and LAK in primary murine spleen cell culture. This report demonstrates that IL-4 selectively down-regulates IL-2 inducible murine CD8- precursors of NK cells. For maximal regulatory effect it is necessary to add IL-4 to cultures before 40 h. Enrichment for NK1.1+ cells failed to recover precursor cells which are down-regulated in overnight cultures or can be cultivated in vitro to yield NK cytolytic activity. Furthermore, phenotypic analysis of effector cells demonstrated a marked inhibition of development of NK1.1+ cells in cultures containing IL-4 plus IL-2 versus IL-2 alone. Thus, it appears that IL-4 down-regulates the precursors of murine NK cells by inhibiting proliferation and/or development. In addition, we show that IL-2-induced murine LAK activity mediated by CD8- precursor cells is unaffected by IL-4, while CD8(+)-derived LAK cells are up-regulated by co-culture with IL-4 and IL-2. Analysis of these data relative to reports documenting down-regulation of human LAK by IL-4 suggests that in vitro cultured, IL-2-activated murine NK cells are the correlates to what are commonly described as human LAK cells. The discrepancy may stem from differences in the characteristics of target cells used in the murine versus the human systems. These results clarify the conflicting reports on the effect of IL-4 on killing activity.     

Interleukin-4 differentially regulates interleukin-2-mediated and CD2-mediated induction of human lymphokine-activated killer effectors.

Natural killer (NK) cells can be differentiated into lymphokine-activated killer (LAK) effectors following stimulation with interleukin (IL)-2. This induction can be negatively regulated by IL-4. In this study, we demonstrate that the stimulation of NK cells through the CD2 pathway with (9-1 + 9.6) monoclonal antibodies can also induce these cells to secrete tumor necrosis factor-alpha (TNF-alpha) and to differentiate into LAK effectors. More importantly, our data indicate that, in contrast to the IL-2-induced LAK generation, the anti-CD2-triggered LAK activity was not regulated by IL-4. IL-4 was found to enhance the LAK activity as well as NK cell proliferation following activation with anti-CD2 by a mechanism involving, at least in part, an increased TNF-alpha production. Using immobilized monoclonal antibodies against the Fc receptor (Fc gamma RIII or CD16) for NK stimulation, we also observed that the anti-CD16-induced LAK activity was not inhibited by IL-4. These data further point to a pivotal role of TNF-alpha as a regulatory cytokine in anti-CD2-induced LAK generation, and suggest that IL-4 could serve as a discriminatory factor between two distinct pathways involved in the activation of non-MHC-restricted cytotoxicity.     

Lymphokine-Activated Killer Cells in Mouse Bone Marrow Chimaeras The Relationship to Natural Killer Cells and to Alloreactive Cytotoxic T Cells

Spleen cells from mouse bone marrow chimaeras were cultured in vitro in mixed lymphocyte cultures (MLC) or in the presence of interleukin 2 (IL-2) without the added alloantigen. Precursors for the nonspecific cytotoxic cells (in this study: lymphokine-activated killer (LAK) cells) lysing natural killer (NK) cell-sensitive YAC-1 lymphoma could be found 10-12 days after the bone marrow reconstitution, simultaneously with the appearance of the NK activity. The ability of LAK cells to lyse NK-resistant tumour targets as well was demonstrated using the P 815 mastocytoma cell line; reactivity against this target was demonstrable 1 week later than the appearance on YAC-1 lysing cells. Phenotypically LAK cells derived from spleen cell cultures of bone marrow chimaeras did not differ from LAK cells derived from normal spleen cell cultures: precursors resided within the Thy 1-, asialo-GM1+ cell population, and effectors expressed both of these antigens. Splenic NK cells of early bone marrow chimaeras (up to 14-18 days after the bone marrow reconstitution) were Thy 1+ cells, and thus LAK cells of bone marrow chimaeras were not derived from these Thy 1+ NK cells. The treatment of effector cells with anti-Thy 1 antibody plus complement (C) abolished the lytic activity totally. However, these cells were not cytotoxic T cells, since alloreactivity, as an indication of the T-cell cytotoxicity, could not be demonstrated until 4-5 weeks after the bone marrow reconstitution.     

Ultrastructural characteristics of lymphokine-activated killer cells of the rat in comparison with natural killer cells

Lymphokine-activated killer (LAK) cells with a broad spectrum of tumor cell killing have been reported to be related to natural killer (NK) cells morphologically and phenotypically. We here examine the ultrastructural characteristics of LAK cells of the rat, comparing them to those of normal and OK-432-activated NK cells. Results show that, five days after the culturing of spleen lymphocytes with human recombinant interleukin-2, there were induced LAK cells, which were large granular lymphocytes and had a cytotoxic capacity against NK-resistant P-815 tumor cells. They were larger in size than NK cells and richer in cell organelles such as ribosomes, rough endoplasmic reticulum, a Golgi apparatus, granules and vesicles. The granules of LAK cells were shown to be related to multivesicular bodies as those of NK cells; they included multivesicular bodies, fully dense granules and intermediate forms between them. The average numbers and sizes of the granules and the proportion of multivesicular bodies and intermediate forms among the total granules were greater in LAK cells than in NK cells. The density of the small vesicles packed in multivesicular bodies and intermediate forms was much higher in LAK cells. At the contacting surface of the LAK cells bound to the target cells, exocytosis of multivesicular bodies was shown to occur. We recognized here two populations of LAK cells with different types of vesicles, one containing rod-cored vesicles and the other a new type of vesicles termed "demilune-cored vesicles". The latter vesicles were the same in size as the rod-cored ones and contained a dense core located eccentrically. Between these two populations of LAK cells, there was no difference concerning the profile of the dense granules. The present study indicates that, although LAK and NK cells share several ultrastructural features, the former show markedly enriched cell organelles, which indicate an accelerated metabolism of the cell for continuous proliferation.     

The effects of recombinant human granulocyte-macrophage colony-stimulating factor on the induction of lymphokine-activated killer cells in vitro.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) was added to a culture of human peripheral blood mononuclear cells in the presence of interleukin 2 (IL-2) in vitro to elucidate its effect on the induction of lymphokine-activated killer (LAK) cells. Viable cell counts of cultured cells and their cytotoxic effects against natural killer (NK) cell-resistant Daudi cells and NK cell-sensitive K562 cells were measured using the trypan blue dye exclusion test and a 51Cr release assay from the tumor cells, respectively. Although GM-CSF alone did not influence either the cytotoxicities or the surface phenotypes of the cultured cells, the viable cell counts were significantly increased by the addition of GM-CSF in the presence of IL-2 (P less than 0.01). These findings indicate that the addition of GM-CSF in the presence of IL-2 during the induction of LAK cells is useful for obtaining a larger number of effector cells which possess substantial cytotoxic activity.     

Noninhibitory binding of human interleukin-2-activated natural killer cells to the germ tube forms of Candida albicans.

During incubation in vitro with yeast or germ tube forms of Candida albicans, only 2 to 6% of freshly isolated human natural killer (NK) cells (> 85% CD16+, CD56+, CD3-; < 15% CD3+; cytolytic for the NK-susceptible target K562 but not for the NK-resistant target DAUDI), were seen to interact with the fungal cells. As seen under the electron microscope, the contact area had a limited extent and was narrow, and neither the surface nor the intracytoplasmic organization of the NK cell was altered. In contrast, more than 30% of interleukin-2-activated NK (LAK) cells (> 96% CD16+, CD56+, CD3-; 1.5% CD3+; cytolytic for both K562 and DAUDI targets) interacted closely with the fungus. This interaction was particularly extensive with the surface of the fungal germ tube that was intimately enveloped by villous protrusions from the lymphocyte surface. The fungus-interacting LAK cell also showed a remarkable redistribution of surface microvilli and polarization of cytoplasmic organelles, such as the Golgi apparatus, centrioles, and granules, toward the area of fungal contact. Together with the elevated cytolytic potential against the K562 and DAUDI targets, all the morphological data suggested the presence of a potentially active lytic machinery in the fungus-interacting LAK cell. Nonetheless, two independent assays for anticandidal activity did not show consistent killing or fungal growth inhibition by either fresh NK or LAK cells. While offering direct evidence of the strong interaction between human LAK cells and the germ tubes, precursors of tissue-invasive hyphal forms of C. albicans, our observations also suggest that this interaction may not be sufficient to kill the fungus or arrest its growth.     

In vivo boosting of lung natural killer and lymphokine-activated killer cell activity by interleukin-2: comparison of systemic, intrapleural and inhalation routes.

Natural killer (NK) cells are thought to play a role in host defence against malignancy and infection, in immunoregulation and as precursor cells in a generation of lymphokine-activated killer (LAK) cells which can lyse NK-resistant tumour cells. As the lung is a major site for malignancy and infection and as there are large numbers of lymphoid cells including NK cells in the interstitial compartment of the lung, we evaluated the capacity of interleukin-2 (IL-2), a lymphokine capable of augmenting NK activity in vitro, to augment lung NK cell activity in vivo, using different routes of IL-2 administration. We compared both systemic (i.v. and i.p.) and local (intrapleural and inhalation) routes of IL-2 administration (50,000 U/daily for 5 days) using CBA mice, assessing NK and LAK cell activity in the spleen (systemic) and in the lung. The target cells used for these studies were the YAC-1 (NK-sensitive) and P815, NO36 and HA56 (NK-resistant, LAK-sensitive) cell lines. Splenic NK activity was increased by 1.4-1.9-fold for i.v./i.p., respectively, compared with controls with both systemic routes of administration, and lung NK activity was increased 3.2-fold and 3.8-fold (i.v./i.p, respectively, P less than 0.05), to levels which were comparable to systemic (splenic) NK activity following the same therapy. Intrapleural IL-2 administration similarly enhanced lung NK activity (3.3-fold) and splenic NK activity (1.3-fold; P less than 0.05 versus controls for both). Surprisingly, inhaled IL-2 suppressed both splenic and lung NK cell activity (84 +/- 8% and 78 +/- 10% suppression, respectively, P less than 0.05). LAK cell activity was also enhanced in the lung by 1.8-8-fold in response to i.v., i.p. and intrapleural IL-2, whereas inhaled IL-2 was ineffective in generating LAK cell activity. These results suggest that the systemic and intrapleural administration of IL-2 effectively boost pulmonary NK and LAK activity whereas inhalation of IL-2 does not. Thus, in clinical situations where boosting of local lung NK or LAK cell activity is desired, these routes of IL-2 administration may be effective.     

Mistletoe Lectin I-Induced Effects on Human Cytotoxic Lymphocytes. I. Synergism with Il-2 in the Induction of Enhanced Lak Cytotoxicity

This report demonstrates that in vitro activation of human cells with the β-galactoside-specific lectin from mistletoe (ML-I) or interleukin-2 (IL-2) results in different patterns of activation and function of cytotoxic cells. It is now well established that natural killer (NK) and lymphokine-activated killer (LAK) cytotoxicity is mainly mediated by resting (NK) and IL-2-activated (LAK) CD56-positive (+) cells respectively. Culture of peripheral blood lymphocytes (PBL) for 3 days with ML-I led to expansion and activation of T cells which demonstrated NK-and LAK-like cytotoxicity. T lymphocyte subset analysis revealed that in total PBL, ML-I preferentially stimulated and expanded CD8+ T cells which mediated the cytotoxic effect. Incubation of highly purified CD8+ T cells alone with ML-I did not lead to induction of cytotoxicity, which required the presence of both CD4+ and CD 14+ (monocytes) cells, suggesting that ML-I does not exert a direct effect on CD8+ T cells. Activation of PBL with both ML-I and IL-2 resulted in simultaneous induction of T and CD56+ cell-mediated NK and LAK cytotoxicity. These data suggest that treatment with ML-I and DL-2 might provide an approach to induce maximum cytotoxicity against tumors and to recruit both T and NK cells for tumor therapy.     

Interleukin-12-stimulated natural killer cells can activate human macrophages to inhibit growth of Mycobacterium avium.

Interleukin-12 (IL-12) is a critical cytokine that affects many of the biological functions of NK cells and T cells. We have previously shown that both human and murine NK cells are important in host defense against Mycobacterium avium complex and act by secreting cytokines that induce macrophages to inhibit the growth of intracellular M. avium. To define the role of IL-12 in M. avium complex infection, we stimulated human NK cells with recombinant human IL-12 at 0.01 to 1 ng/ml for 24 h and used the tissue culture supernatant to treat human monocyte-derived macrophage monolayers infected with M. avium. IL-12 had no direct effect on M. avium-infected macrophages, but culture supernatant from IL-12-treated NK cells activated macrophages to inhibit the growth of intracellular M. avium in a dose-dependent manner. Stimulation of NK cells with IL-12 in combination with tumor necrosis factor alpha (TNF-alpha) or IL-1 increased the ability of supernatant from NK-cell culture to limit M. avium growth within macrophages, compared with that of culture supernatant from IL-12-treated NK cells. Results with supernatant from nonstimulated NK cells were similar to those with supernatant from untreated controls. Treatment of supernatant from IL-12-stimulated NK cells with anti-TNF-alpha, anti-granulocyte-macrophage colony-stimulating factor, but not anti-gamma interferon antibodies decreased the ability of NK-cell supernatant to induce anti-M. avium activity in infected macrophages. Treatment of macrophage monolayers with anti-transforming growth factor beta antibody before adding supernatant from IL-12-stimulated NK cells was associated with an increase of anti-M. avium activity compared with that of supernatant from IL-12-treated NK cells. These results suggest that IL-12 has a role in host defense against M. avium and that the effect of IL-12 is dependent chiefly on TNF-alpha and granulocyte-macrophage colony-stimulating factor.     

Bone marrow progenitors cultured in the presence of granulocyte-macrophage colony-stimulating factor versus macrophage colony-stimulating factor differentiate into macrophages with distinct tumoricidal capacities

Bone marrow-derived cells from C3H/HeJ mice were cultured in the presence of recombinant murine granulocyte-macrophage colony-stimulating factor (rGM-CSF) or highly purified murine macrophage colony-stimulating factor (CSF-1) for 7 days. Following this 7-day culture period, mature macrophages were harvested and replated at precise densities in the absence of exogenous rGM-CSF or CSF-1, and assayed in a two-signal tumoricidal assay. Cultures were stimulated with medium only or with combinations of recombinant interferon-gamma (rIFN-gamma) as the "priming" signal, and/or butanol-extracted lipopolysaccharide (But-LPS) as the "triggering" signal for 24 hr. At this time, 51Cr-labeled, P815 tumor target cells were added, and the percent tumor cell cytotoxicity was determined after 16 hr. Macrophages derived under the influence of rGM-CSF exhibited significant tumoricidal capacity with medium alone (16 +/- 5%). The addition of "priming" signal only (i.e., rIFN-gamma, 10.0 U/ml) significantly increased tumoricidal capacity to 31 +/- 9%. Treatment with But-LPS alone did not alter the basal tumoricidal activity of rGM-CSF-derived macrophages. Combinations of rIFN-gamma (10.0 U/ml) and But-LPS (0.5-5.0 micrograms/ml) generated highly tumoricidal macrophages (50-60% tumor cell cytotoxicity). In contrast, medium-treated CSF-1-derived macrophages exhibited a significantly lower basal level of tumor cytotoxicity (6 +/- 3%). Unlike rGM-CSF-derived macrophages, treatment of CSF-1-derived macrophages with high concentrations of rIFN-gamma alone did not increase significantly the level of cytotoxicity above that of medium-treated cultures. However, CSF-1-derived macrophages responded to the highest concentrations of But-LPS (5.0 micrograms/ml) to increase tumoricidal activity from 6 +/- 3% to 17 +/- 5%. Optimal tumoricidal activity (44 +/- 17%) was observed when CSF-1-derived macrophages were treated simultaneously with high concentrations of both rIFN-gamma and But-LPS. Thus, macrophages derived from bone marrow progenitors in either rGM-CSF or CSF-1 exhibited tumoricidal capacities that differed in basal activity as well as in their requirements for and sensitivities to "priming" and "triggering" signals.     

Identification of cytokines which enhance (CSF-1, IL-3) or restrict (IFN-gamma) growth of intramacrophage Listeria monocytogenes

Murine peritoneal macrophages were isolated by adherence and their listericidal activity assessed in the presence or absence of selected cytokines. Untreated macrophages were not highly listericidal, showing moderate killing in the first 2 h after infection, and allowed progressive microbial growth thereafter (up to 9 h). Pre-treatment of cells with 10 to 100 U/ml of IFN-gamma allowed macrophages to develop sustained listericidal activity for the 9-h observation period, with a 2-log reduction of Listeria CFU per monolayer. Pulsing of cells with TNF-alpha alone did not result in enhanced microbicidal activity but TNF-alpha potentiated IFN-gamma-induced listericidal activity, resulting in high levels of killing when both cytokines were present. Conversely, macrophages pre-treated with interleukin-3 (IL-3) or colony-stimulating factor-1 (CSF-1) were found to be much more permissive for Listeria growth. Neither IL-3 nor CSF-1 abrogated IFN-gamma-induced listericidal activity. Moreover, neither IL-3 nor CSF-1 had any effect on the ability of macrophages to develop a respiratory burst following Listeria infection, as judged by H2O2 release following in vitro infection. Overall, these results suggest that different cytokines may have opposing effects on intracellular microbial growth, and that the balance of cytokine production in vivo may determine the resistance or susceptibility of the infected host.     

Differential effects of IL-4 and IL-10 on IL-2-induced IFN-gamma synthesis and lymphokine-activated killer activity.

Culture of human peripheral blood mononuclear cells (PBMC) with IL-2 stimulates synthesis of cytokines and generation of lymphokine-activated killer (LAK) activity. Both IL-4 and IL-10 [cytokine synthesis inhibitory factor (CSIF)] inhibit IL-2-induced synthesis of IFN-gamma and tumor necrosis factor (TNF)-alpha by human PBMC. However, unlike IL-4, IL-10 inhibits neither IL-2-induced proliferation of PBMC and fresh natural killer (NK) cells, nor IL-2-induced LAK activity. Moreover, IL-4 inhibits IL-2-induced IFN-gamma synthesis by purified fresh NK cells, while in contrast the inhibitory effect of IL-10 is mediated by CD14+ cells (monocytes/macrophages). IL-10 inhibits TNF-alpha synthesis by monocytes or monocytes plus NK cells, but not by NK cells alone. These results suggest that IL-4 and IL-10 act on NK cells via distinct pathways, and that IL-2-induced cytokine synthesis and LAK activity are regulated via different mechanisms.     

Colony-stimulating factors increase resistance to atypical mycobacteria in resistant mice, whereas they decrease resistance in susceptible strains of mice

Inbred strains of mice, notably the susceptible C57BL/6 and the resistant A/J strains of mice, were infected with a strain of Mycobacterium evium. The infection in the visceral organs of mice was then studied, and the effect of colony-stimulating factors, i.e., interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), and macrophage colony-stimulating factor (CSF-1) on the infectious process was evaluated. Infusion of GM-CSF, CSF-1, and IL-3 led to a significant, albeit rather modest, increase in the mycobacterial resistance of A/J mice, as seen by a decrease in the number of colony-forming units (CFU) in the organs. Conversely, these CSFs dramatically increased the susceptibility of C57BL/6 mice, as seen by increased bacterial numbers in the spleens and livers. In vitro studies demonstrated that resident peritoneal macrophages from susceptible mice were more permissive than cells from resistant mice for mycobacterial growth. Application of CSFs on peritoneal macrophage monolayers led to an increased growth in both A/J and C57BL/6 monolayers for IL-3 and CSF-1 and a small microbiostatic effect for GM-CSF. Cytokine treatment did not, however, change the resistance/susceptibility phenotype of isolated macrophages. Our results indicate that CSFs may exert beneficial or detrimental effects on resistance to mycobacteria depending on the host genetic make up.     

T cell nature of some lymphokine-activated killer (LAK) cells. Frequency analysis of LAK precursors within human T cell populations and clonal analysis of LAK effector cells

The cell lineage of the lymphokine-activated killer (LAK) cells has been reinvestigated. Both T and non-T cells, isolated on the basis of rosette formation with sheep erythrocytes (E), generated LAK activity after 3-4 days of culture in recombinant interleukin 2 (rIL 2) in 8 different individuals tested. By applying a microculture technique which allows clonal expansion of virtually all E rosetting T cells, we further analyzed the frequency of clonogenic LAK precursors within T cell populations. Approximately 1 of 25 T cells was found to be a LAK precursor. Moreover, microcultures with LAK activity lysed both the natural killer-sensitive K562 cell line and the P815 target cells in the presence of phytohemagglutinin (PHA). Since cytolytic T lymphocytes capable of lysing P815 cells in the PHA-dependent assay were approximately 1/3, it is evident that only a minor subset of cytolytic T lymphocyte precursors can acquire LAK activity even in the presence of large amounts of IL 2. Several LAK clones obtained by limiting dilution were further expanded and analyzed for their phenotypic and functional properties. Twelve out of 14 clones analyzed expressed the T3+ T11+ phenotype whereas 2 were T3- T11+. All had maintained their original cytolytic pattern; moreover, the large majority of the T3+ clones produced IL 2 and interferon-gamma following PHA stimulation.     

Differential cytokine regulation of natural killer cell-mediated necrotic and apoptotic cytotoxicity.

Natural killer (NK) cells can kill target cells by either necrotic or apoptotic mechanisms. Using the 51Cr-release assay to measure necrotic death of target cells, neonatal NK cells had low NK activity (K562 targets) and high lymphokine-activated killer (LAK) activity (Daudi targets) compared with adult cells, as has been previously reported. Using a 125I-deoxyuridine (125I-UdR) release assay, cord cells were shown to also have higher apoptotic LAK activity against YAC-1 target cells. Interleukin-4 (IL-4) inhibited interleukin-2 (IL-2)-induced necrotic killing of target cells by adult effectors but had no such inhibitory effect on cord cells. In contrast, IL-4 inhibited both adult and cord LAK cytotoxicity of YAC-1 target cells by apoptotic mechanisms with higher suppression observed in cord cell preparations. Using a colorimetric substrate conversion assay, IL-2 induced higher, and IL-4 had a more significant suppressive effect on, cord cell granzyme B enzyme activity compared with adult cells, paralleling apoptosis cytotoxicity data. Co-culture of either adult or cord LAK cells with IL-4 had a similar inhibitory effect on granzyme B protein expression, as detected by Western blotting. In contrast, IL-4 did not inhibit perforin expression, thereby defining IL-4 as a cytokine that can differentially regulate the NK cell-mediated cytotoxicity processes of apoptosis and necrosis. The differential sensitivity of cord cells to cytokine regulation of cytotoxicity may also have implications for cord blood transplantations, as NK cells are known to function as an effector cell in both graft-versus-host disease and in the graft-versus-leukaemia phenomena.     

Sperm with damaged membranes are profoundly at risk to have caspases 8, 9 and 3 activated

PROBLEM:  It is almost dogma that IL-2 is not expressed at the M–F interface during normal pregnancy. However, recent results by ours and others clearly showed that IL-15-Th1 type cytokine which shares many similarities with IL-2 is expressed at the interface. IL-15 can affect cytolytic activity of maternal decidual lymphocytes which heavily infiltrate maternal decidua during the first trimester pregnancy. These cells are in a direct contact with trophoblastic cells. IL-18 is a recently discovered Th1 type cytokine with many interesting functions. The aim is to examine IL-18 distribution at the interface and its potential in up-regulating peripheral blood (PB) and decidual lymphocytes (DL) cytotoxicity. Th1 activated lymphocytes are LAK cells and they can kill by both Perforin and Fas pathways in non MHC restricted manner.
METHODS:  PBL and DL were obtained from elective pregnancy termination of pregnancy. IL-18 and IL-18R expression was detected by flow cytometry and immunohistology and cytolytic potential by cytotoxicity against K-562 (NK sensitive) and P815 (NK resistant) cell lines.
RESULTS:  IL-18 positive cells were found in the suspension of Decidual adherent cells and IL-18 R expressions at the trophoblastic cells of villi. Both IL-15 and IL-18 are increasing cytolytic potential of PBL and DL against NK sensitive cell line. Decidual lymphocytes are activated cells with the potential of killing NK resistant but LAK sensitive lines and this is mediated by both perforin and Fas pathways.
CONCLUSIONS:  Physiological and pathophysio- logical role(s) of cytolytic pathways and Th1 cytokines (IL-15 and IL-18) at the interface will be discussed.