Similarities and distinctions between murine natural killer cells and lymphokine-activated killer cells

Pretreatment of mice with rabbit anti-asialo GM1 removes both natural killer (NK) effector cells and NK cells responsive to interleukin 2 (IL-2). Spleen cells from these mice do possess normal lymphokine-activated killer (LAK) activity. Young mice (less than 3 weeks of age) do not have NK activity and do not possess IL-2-inducible NK effector cells. Similarly to anti-asialo GM1-treated mice, LAK cells can be generated from these mice. While these experiments indicate clear distinctions between a certain level of NK and LAK precursors, the distinctions are not as clear when analyzing mice congenitally deficient in NK cells. Beige mice which lack NK effector cells and IL-2-inducible NK cells also lack the ability to generate LAK cells. The relationships and differences between NK- and LAK-cell precursors and effectors are discussed.     

Supplementation with selenium augments the functions of natural killer and lymphokine-activated killer cells

This study examined the effects of dietary (2.0 ppm for 8 wk) and in vitro (1×10⁻⁷ M) supplementation with selenium (Se, as sodium selenite) on the activity of spleen natural killer (NK) cells and plastic-adherent lymphokine-activated killer (A-LAK) cells from C57B1/6J male mice. Dietary supplementation with Se resulted in a significant increase in the lytic activity of activated NK cells, and cells from these highly lytic effector cell populations expressed significantly higher numbers of intermediate affinity interleukin-2 receptors (II-2R)/cell. In the presence of high concentrations of II-2 and 1×10⁻⁷ M Se, resting populations of spleen NK cells developed into A-LAK cells that had a significantly enhanced ability to proliferate, as indicated by the significantly higher amounts of nuclear³H-thymidine incorporation, and a significantly augmented cytolytic activity against both NK-sensitive and NK-resistant target cells. Se appears to enhance the lytic activity of activated NK cells and to augment the proliferation, expansion, and lytic activity of A-LAK cells in the presence of high concentrations of Il-2 through its ability to enhance the expression of intermediate affinity Il-2R on these cells.     

Lysis of fresh murine mammary tumor cells by syngeneic natural killer cells and lymphokine-activated killer cells

Summary We have compared the ability of natural killer (NK) cells from two substrains of C3H mice that differ with respect to their susceptibility to the development of mammary adenocarcinomas to lyse fresh syngeneic mammary tumor cells. Single cell suspensions of mammary tumors from retired breeder females were used as targets in 22-h ⁵¹Cr-release cytotoxicity assays with syngeneic NK cells. Tumor cell suspensions were prepared by enzymatic digestion of finely minced tissue followed by centrifugation through a discontinuous Percoll gradient. Effector cells were prepared by passing spleen cells over nylon wool followed by centrifugation through Percoll fraction 7. Syngeneic NK cells had significant levels of lysis against 5/8 tumors studied. NK cells from low risk animals (C3Heb/FeJ) consistently demonstrated greater cytotoxicity against tumor cell preparations than did effectors from the high tumor substrain (C3H/OuJ). Study of cytocentrifuge preparations stained with Wright-Giemsa revealed that the two substrains were identical with respect to the number of azurophilic granules present in the cytoplasm of their NK cells. We have also shown that lymphokine-activated killer (LAK) cells can be generated from splenocytes in C3H mice. While LAK cells from both substrains were capable of lysing fresh syngeneic mammary tumor cells in vitro, LAK cells from the animals at high risk for the formation of mammary adenocarcinomas had greater cytotoxicity against tumor cell suspensions than LAK cells from the low tumor substrain.     

Comparison of murine lymphokine-activated killer cells, natural killer cells, and cytotoxic T lymphocytes

Precursors and effectors of murine lymphokine-activated killer cells, natural killer cells, and cytotoxic T lymphocytes are compared. Natural killer cells are resistant to gamma-irradiation (1000 R) whereas precursors of lymphokine-activated killer cells and cytotoxic T lymphocytes are sensitive. Lower doses of gamma-irradiation (500 R) remove precursors for cytotoxic T lymphocytes but not lymphokine-activated killer cells. In addition, lymphokine-activated killer cells are regenerated before classical CTL after sublethal doses of gamma-irradiation. Natural killer cells are resistant to anti-Thy 1 and C' and anti-thymocyte serum, but sensitive to anti-asialo GM1 and complement. Precursors of cytotoxic T lymphocytes are sensitive to anti-Thy 1 and complement and anti-thymocyte serum, but are resistant to anti-asialo GM1 and complement. Precursors of lymphokine-activated killer cells are partially sensitive to anti-Thy 1 and complement and anti-thymocyte serum, but are resistant to anti-asialo GM1 and complement. Effector cells of cytotoxic T lymphocytes are sensitive to anti-Thy 1 and complement and resistant to anti-asialo GM1 and complement. Lymphokine-activated killer cell effectors are sensitive to anti-asialo GM1 and complement at 24 hr after activation. These effectors are more closely aligned with classical natural killer effectors. Lymphokine-activated killer effectors, 7 days after activation, are resistant to anti-asialo GM1 and complement and sensitive to anti-Thy 1 and complement. Relationships and differences among these cytotoxic subsets are discussed.     

Lysis of human solid tumor cells by lymphokine-activated natural killer cells

The ability of NK cells to lyse noncultured solid tumor cells was investigated, and the results were compared with lysis of K562. Purified NK cell fractions separated by either Percoll centrifugation or a cell sorter exhibited higher level of lysis against noncultured melanoma cells than did NK-depleted cell fractions. However, the level of lysis was low (less than 10% lysis). Adding recombinant interleukin 2 (rIL 2) to the 4-hr assay induced significant lysis (more than 10%) of noncultured melanoma cells in 18 of 23 (78%) Percoll-enriched NK cell fractions and seven of 11 (64%) sorted Leu-11a+ cells at an E:T ratio of 80 and 10, respectively. In contrast, only two of 13 (14%) PBMC, five of 17 (29%) Percoll-decreased NK cell fractions, and one of 12 (8%) sorted Leu-11a- cells lysed noncultured melanomas in the presence of rIL 2. rIL 2 induced NK cells to lyse noncultured lung and breast cancer cells, as well as melanoma tumors. Exposure of NK cells to 2000 rad radiation abrogated the rIL 2-induced cytotoxicity against noncultured melanomas. Preculture of PBMC for 18 hr with recombinant interferon-gamma (rIFN-gamma) resulted in a modest level of lysis of non-cultured melanomas by sorted Leu-11a+ cells. Adding rIL 2 to the assay increased the cytotoxic activity in both rIFN-gamma-activated Leu-11a+ and Leu-7+ NK subsets. The level of noncultured tumor lysis correlated well with that of K562 lysis in all of the experiments. Purified NK cell fractions in rIL 2 cultures increased cytotoxic activity against noncultured tumor cells with incubation time for up to 3 days, and the level of NK cell-mediated lysis was dependent on both doses of rIL 2 and length of incubation. In contrast, both NK-depleted and sorted Leu-11a- cells demonstrated very low levels of solid tumor lysis after 3-day cultures with a high dose of rIL 2. Killer cell precursors induced by 3-day cultures of sorted cell fractions with rIL 2 and rIFN-gamma were found in both Leu-11a+ and Leu-7+ NK subsets, but not Leu-4+ or Leu-3a+ T lymphocytes. These results indicate that NK cells become cytotoxic for noncultured solid tumor cells by a brief contact with rIL 2, and increase cytotoxic activity after culture with rIL 2.     

Chemotherapy-induced modulation of natural killer and lymphokine-activated killer cell activity in euthymic and athymic mice

Combinations of chemotherapy and interleukin-2 (IL-2) aimed at improving therapeutic efficacy in cancer patients have generally proved disappointing. Although chemotherapy blocks tumor growth and sometimes boosts immune functions, most drugs are immunosuppressive, at least transiently. Therefore, it is reasonable to assume that maximal exploitation of the immunostimulatory and antitumor activity of both modalities requires careful coordination of chemotherapy and IL-2 timing. We analyzed the temporal effect of 5-fluorouracil (5-FU, 100–120 mg/kg), cyclophosphamide (CY, 100 mg/kg), Adriamycin (8 mg/kg) and dacarbazine (100 mg/kg) on the activation of natural killer/lymphokine-activated killer (NK/LAK) cells by IL-2 in several strains of euthymic mice and in athymic nude mice. Following in vivo or in vitro exposure to IL-2 1–15 days after chemotherapy, the total lytic activity of the spleen and the number of LAK precursors (LAK-p) were measured. In euthymic mice injected with IL-2 (5×10⁴ Cetus units twice daily for 4–5 days), 5-FU augmented (up to 37-fold, days 1–9) and CY reduced (up to day 6) LAK activity, as compared with that in the IL-2 control. In bulk cultures containing IL-2 (1000 CU/ml, 3–4 days), both 5-FU and CY reduced LAK activity of euthymic mice splenocytes for up to 6 days after chemotherapy, which was followed on day 9 by full recovery. In splenocytes of nude mice, 5-FU increased and CY diminished LAK activation in bulk cultures, starting 3 days after chemotherapy. In athymic mice, 5-FU markedly augmented the total number of LAK-p/spleen (up to 30-fold, days 3–9), as determined by limiting-dilution cultures with IL-2 (for 7–8 days). In euthymic mice, in contrast, LAK-p levels decreased for up to 6–9 days after treatment with 5-FU, Adriamycin or dacarbazine, later recovering to pretreatment levels, whereas CY markedly increased LAK-p (up to 15-fold) when administered 6–12 days before limiting-dilution culture initiation. The effect of chemotherapy on LAK and NK activity was essentially similar. In other experiments, a subset of asialoGM1-LAK-p was found in the spleens of 5-FU-treated mice, but not in untreated mice. Our results suggest that the immunomodulatory effect of chemotherapy on NK/LAK activity in mice is variable and largely depends on the drug itself, the interval between chemotherapy and IL-2 administration, the strain of mice and the assay used.     

Lymphokine-activated killer cells in rats: generation of natural killer cells and lymphokine-activated killer cells from bone marrow progenitor cells

The coculture of rat bone marrow cells with recombinant interleukin-2 induced the generation of cells mediating natural killer (NK) activity and subsequent lymphokine-activated killer (LAK) activity depending upon the dose of IL-2 and time of culture. NK activity was detected as early as 4 to 5 days after the addition of IL-2 and could be evoked with as little as 5 to 50 U/ml. The induced NK cells had large granular lymphocyte (LGL) morphology and expressed 0X8 and asialo GM1 surface markers but did not express 0X19 or W3/25 markers. LAK activity was detected only after 5 days of culture, and required above 100 U/ml IL-2. Cells mediating LAK activity also expressed 0X8 and asialo GM1 but not 0X19. The generation of detectable NK and subsequent LAK activity was due to induction of early progenitor cells and not contaminating mature LGL/NK cells within the bone marrow population since of removal of such mature NK cells with L-leucine methyl ester (L-LME) did not affect the subsequent generation of either activity. Moreover, the removal of actively dividing cells as well as mature NK cells from the bone marrow by treatment with 5-fluorouracil (5-FU) in vivo enriched the remaining bone marrow population for both NK and LAK progenitor cells. The phenotype of the L-LME- and 5-FU-resistant NK and LAK progenitor cells within populations of bone marrow was determined by antibody plus complement depletion analysis. Although treatment of normal bone marrow with anti-asialo GM1 + C reduced the induction of NK and LAK activity in 5-day cultures, treatment of 5-FU marrow with anti-asialo GM1 + C did not affect either activity. Treatment with a pan-T cell antibody + C did not affect the development of NK or LAK activity under any conditions. Thus, the 5-FU-resistant NK/LAK progenitors were asialo GM1 negative but became asialo GM1+ after induction by IL-2. Finally, evidence that bone marrow-derived LAK cells were generated directly from the IL-2-induced NK cells was obtained by treating the IL-2-induced LGL/NK cells with L-LME.(ABSTRACT TRUNCATED AT 400 WORDS)     

Studies on the relationship of human natural killer and lymphokine-activated killer cells with lysosomal staining and analysis of surface marker phenotypes

We have previously demonstrated that natural killer (NK) cells are lysosome-rich and stain more intensely with lysosomotropic agents such as neutral red and quinacrine (Qu) than do non-NK cells. In this study we combined the quantitation of Qu staining with surface marker staining to define subpopulations of NK cells. While all NK activity was contained within the Qu+ population, most but not all NK cells expressed the surface marker CD16. A subpopulation of NK cells was found to be Qu+CD16- composed of medium- to large-sized cells with a granular appearance on Giemsa staining. Culture with interleukin-2 (IL-2) induced enhanced cytotoxicity in peripheral blood lymphocytes (PBL) against NK-sensitive and NK-resistant tumor cells. Like NK cells, these lymphokine-activated killer (LAK) cells were predominantly Qu+CD16+. However, some LAK cells were Qu+CD16-. The Qu+CD16+ cells were typical large granular lymphocytes (LGL). The Qu+CD16- cells were also large lymphocytes, more than 50% of which were proliferating. However, the granulation in some Qu+CD16- cells, as detected by Giemsa staining, was more prominent and numerous than others in the same population. No LAK activity was ever detected in Qu- cells, which were uniformly small lymphocytes. Quantitation of Qu staining in effector cells was therefore demonstrated to have a good correlation with NK and LAK functions, and with surface markers can help to characterize both types of cells. Moreover, these results indicate that both NK and LAK populations include a small subset of CD16- cells in each.     

Generation and characterization of purified adherent lymphokine-activated killer cells in mice

During the incubation of murine spleen, lymph node, or bone marrow cells with IL-2 (1000 U/ml) a small percentage of cells became adherent to the surface of plastic tissue culture flasks. After removal of the non-adherent lymphoid cells, plastic adherent lymphokine-activated killer (LAK) cells could be efficiently expanded in the presence of IL-2. Plastic adherent-derived A-LAK cells were characterized by high rates of proliferation and their cytotoxic activity was more than 10 fold higher than LAK cells generated in the bulk (unfractionated) spleen cell cultures. A-LAK cells could be continuously generated from the non-adherent cell population. Using multiple transfers (every 1 to 2 days) of non-adherent LAK cells into new flasks, new rounds of plastic adherent cells were generated with high expansion capability and high levels of cytotoxic activity. Morphologically, A-LAK cells were large granular lymphocyte and phenotypically expressed markers characteristic of NK cells (asialo GM1+, NK1.1+, Qa5+, Ly-6.2+, Thy-1.2+, but negative for Lyt-2.2 and L3T4). A-LAK cells generated from mice of different strains expressing low and high levels of NK cell activity were equally highly cytotoxic. However, A-LAK cells obtained from nude or beige mice had relatively lower levels of cytotoxicity. Stimulation of NK cell activity by poly I:C or inhibition by in vivo or in vitro treatment with anti-asialo GM1 serum did not affect the generation of A-LAK cells. A-LAK cells derived from spleen or bone marrow of C57BL/6 or nude mice treated with anti-asialo GM1 serum were found to be asialo GM1+ suggesting that A-LAK cell could be generated from the asialo GM1- precursor cells. Expansion of plastic adherent A-LAK cells in the presence of IL-2 could provide large numbers of highly purified cytotoxic A-LAK cells suitable for cancer immunotherapy.     

Role of lymphokine-activated killer cells as mediators of veto and natural suppression

Fresh bone marrow cells have veto activity but little if any NK activity. By contrast, lymphokine-activated bone marrow cells have potent natural suppressor as well as veto activity, and also have cytolytic activity characteristic of lymphokine-activated killer cells. Veto activity of fresh bone marrow cells is eliminated by 9 Gy irradiation and by depletion of cells expressing Qa-2, but is unaffected by removal of cells expressing Thy-1, Qa-5, Ly-5, or asialo GM1. By contrast, the veto and NS activities of lymphokine-activated bone marrow cells are both abrogated by C lysis depletion of cells expressing Qa-2, Qa-5, Thy-1, asialo GM1, NK1, and Ly-11, but are unaffected by depletion of cells expressing Ly-2. Bone marrow cells depleted of Qa2+ cells fail to generate veto or natural suppressor activity when cultured in Con A-conditioned medium, unlike bone marrow cells depleted of mature NK1.1+ NK cells. Cloned NK cell line F8 is able to mediate both natural suppression and veto. These findings indicate that bone marrow veto and natural suppression are not mediated by T or NK cells present de novo in the bone marrow, but are dependent on proliferating cells that phenotypically resemble pre-NK cells. The progeny of these cells have the phenotype and functional activity of lymphokine-activated killer cells, and are capable of directly mediating both veto and natural suppression.     

Adherent lymphokine-activated natural killer cells in normal and severe combined immunodeficiency mice: large granular lymphocytes with natural killer cell phenotype and high cytolytic activity

Plastic-adherent lymphokine-activated natural killer (LANK) cells were generated from nylon wool-nonadherent murine splenocytes cultured in recombinant interleukin-2 (IL-2). Under such conditions, adherent lymphokine-activated killer cells capable of killing natural killer (NK)-resistant targets were not generated. Adherent LANK cells proliferated rapidly and closely resembled NK cells in their morphology, cytotoxic reactivity, and surface marker expression. Mice with severe combined immunodeficiency (scid) were used to generate adherent LANK cells to define the role of T cells in LANK cell development. Scid lymphocytes responded to IL-2 by becoming adherent LANK cells with potent NK-like activity, suggesting that soluble lymphokines other than IL-2 that may have been produced by T cells were not required for the generation of LANK cell activity in mice.     

Human killer cells and natural killer cells: distinct subpopulations of Fc receptor-bearing lymphocytes

Unstimulated human peripheral blood lymphocytes were depleted of K cells, which mediate antibody-dependent cellular cytotoxicity (ADCC) without removing NK cells, which mediate natural killing (NK). K cell depletion was achieved by buoyant centrifugation removal of lymphocytes that bound to glutaraldehyde-treated P815-AB cells at high lymphocyte-to-target ratios. Likewise, NK cells were removed with glutaraldehyde-treated K562 cells without removing K cells. Furthermore, both cytotoxic cell populations were observed directly in one agarose single-cell cytotoxic assay (ASCA) using P815-AB and K562 cells simultaneously as target cells. Moreover, the percentage of total cytotoxic cells was equal to the sum of the percentage of K and NK cells observed in separate ASCA. Collectively, these results indicate that K cells and NK cells are distinct subsets of FcR-bearing lymphocytes. One subset, K cells, has more avid Fc receptors (fcR) than NK cells and are 'activated' via thier FcR to kill antibody-coated target cells. The second subset, NK cells, have less avid FcR and are not 'activated' through their FcR to kill antibody-coated target cells.     

Differential expression of lymphokine-activated killer cells and natural killer cells in adoptive transfer experiments utilizing fractionated bone marrow

Precursors of murine natural killer (NK) cells and lymphokine-activated killer (LAK) cells can be distinguished by utilizing an adoptive transfer system in which donor bone marrow is fractionated on Percoll discontinuous gradients. Although precursors of LAK cells are present in all fractions, one fraction (greater than 65% Percoll) contains LAK precursors and is depleted of NK precursors. Both in vitro NK activity and in vivo hybrid resistance is abrogated in recipients of bone marrow from the greater than 65% Percoll fraction, whereas LAK activity can be readily demonstrated.     

Infiltrating decidual natural killer cells are associated with spontaneous abortion in mice

Immunohistochemistry was used to study a murine model which spontaneously aborts at a frequency of 25 to 30%. Our results show that natural killer (NK) cells are not only the predominant infiltrating cells in aborting feto-placental units, but that they also appear in a similar proportion of feto-placental units before abortion is detectable. The frequency of feto-placental units with significantly elevated NK infiltrates corresponds to the subsequent abortion frequency, indicating a causal relationship. Immunization of the mother with BALB/C splenocytes prevents these NK infiltrates and decreases the abortion frequency to normal levels. These results suggest for the first time that maternal NK cells may have an instrumental role in the etiology of spontaneous abortion.     

Human oncogene-transfected tumor cells display differential susceptibility to lysis by lymphokine-activated killer cells (LAK) and natural killer cells

NIH 3T3 tertiary transfectants containing the N-ras or c-Ha-ras oncogenes derived from human tumors were tested for susceptibility to lymphokine-activated killer (LAK) cell and natural killer (NK) cell lysis. N-ras tertiary transfectants contained a human acute lymphocytic leukemia-derived N-ras oncogene. C-Ha-ras transfectants contained either the position 61-activated form of the oncogene (45.342, 45.322, and 45.3B2) or the position 12-activated form (144-162). In 4 hr 51Cr release assays, seven of seven in vivo grown human oncogene transfected NIH 3T3 fibroblasts were lysed by murine LAK effectors, whereas six of seven were lysed by human LAK effectors. There was no difference in susceptibility to lysis between cells transfected with the N-ras oncogene, the position 61 activated c-Ha-ras oncogene, or the position 12 activated c-Ha-ras oncogene. Cultured NIH 3T3 fibroblasts, as well as in vitro and in vivo grown NIH 3T3 tertiary transfectants were resistant to lysis by murine NK effectors and were relatively resistant (4/6 were not lysed) to lysis by human NK effectors. We conclude that human oncogene-transfected tumors are susceptible to lysis by both murine and human LAK cells while being relatively resistant to lysis by murine and human NK cells. Different oncogenes or the same oncogene activated by different point mutations do not specifically determine susceptibility to lysis by LAK or NK. Also the presence of an activated oncogene does not appear to be sufficient for inducing susceptibility to these cytotoxic lymphocyte populations.     

Renewal of natural killer cells in mice having elevated natural killer cell activity

The present study was designed to examined the dynamics of splenic natural killer (NK) cells under two conditions of enhanced NK cell activity: (1) CBA/J mice given polyinosinic-polycytidylic acid (poly-I:C), an NK-cell-enhancing agent, and 62) untreated athymic nude (nu/nu) mice. The 'total NK cell activity' of the spleen (percentage specific lysis corrected for changes in organ cellularity) increased 5-fold and 2.7-fold after poly-I:C treatment for 1 day and 4 days, respectively. An injection of hydroxyurea (HU), a cell-cycle-toxic drug, given together with either poly-I:C or saline to CBA/J mice resulted in both cases in a 25% reduction in total NK cell activity 1 day later. This suggests that the renewal rate of nondividing NK cells is similar in poly-I:C-treated and saline-injected mice, and that the NK-enhancing effect of poly-I:C is not due to a stimulation of proliferation among NK cell precursors. HU administered simultaneously with poly-I:C or saline for 4 days eliminated NK cell activity in both cases, indicating that spleen NK cell activity is mediated almost entirely by newly formed (less than or equal to 4 days) cells. In nude mice, NK cell activity was assayed at various intervals after an HU depletion period of 2 days. NK depletion was initially more rapid in nu/nu mice than in control (nu/+) mice, although equally profound, and the subsequent recovery of NK cell activity after cessation of HU was also more rapid than in control (nu/+) mice.(ABSTRACT TRUNCATED AT 250 WORDS)     

Identification and characterization of a cell-surface molecule that is selectively induced on rat lymphokine-activated killer cells

We have identified a 40- to 45-kDa cell-surface molecule designated gp42, that is expressed in high levels by rat lymphokine-activated killer (LAK) cells of NK cell origin. gp42 cannot be detected on the precursors of LAK cells and is not present on resting or activated T cells. Rather, expression of gp42 is selectively induced on NK cells by the high concentrations of rIL-2 that are required for the induction of LAK activity. Although the function of gp42 is not known, the selective nature of its expression suggests a role for this molecule in regulating responses that are unique to IL-2-activated NK cells.     

IL-4-induced lymphokine-activated killer cells. Lytic activity is mediated by phenotypically distinct natural killer-like and T cell-like large granular lymphocytes

The purpose of the current study was to characterize lymphokine-activated killer (LAK) activity induced with IL-4/B cell stimulatory factor-1 and to compare IL-4-induced LAK activity with IL-2-induced LAK activity. Culture of murine lymphocytes with high concentrations of IL-4 induced nonspecific lytic activity against a wide variety of tumors. Lytic activity induced by IL-4 increased with increasing concentrations of IL-4 over the range of 1.0 to 25 ng/ml. The kinetics of LAK induction by IL-4 and IL-2 were similar; however, IL-4 was less effective than IL-2 in maintaining lytic activity for longer culture periods and provided lower viable cell yields than did IL-2. Similar to IL-2, IL-4 induced blastogenesis and the generation of large granular lymphocytes, all LAK activity observed was exclusively associated with the large granular lymphocyte fraction, and the cytolytic effector cells were heterogeneous in regards to cell surface phenotype. The majority of IL-4-induced lytic activity was associated with mutually exclusive NK-like (i.e., NK-1.1+ Lyt-2-) and T cell-like (i.e., NK-1.1- Lyt-2+) LAK cells. The precursors for each subset were distinct and expressed the asialo-GM1+ Lyt-2- and the asialo-GM1+ Lyt-2+ phenotypes, respectively. Although IL-4-induced LAK effector cells were morphologically and phenotypically similar to IL-2-induced LAK cells, IL-2 generated equivalent numbers of T cell-like and NK-like LAK cells, whereas IL-4 generated 3.5-fold more T cell-like LAK cells than NK-like LAK cells. It might eventually be possible to exploit the preferential activation of T cell-like LAK by IL-4 for therapeutic advantage.     

Leukoregulin up-regulation of tumor cell sensitivity to natural killer and lymphokine-activated killer cell cytotoxicity

The present investigation demonstrates that leukoregulin, a cytokine secreted by natural killer (NK) lymphocytes up-regulates the sensitivity of tumor cells to lymphokine-activated killer (LAK) cell cytotoxicity. It has been previously established that leukoregulin increases the sensitivity of sarcoma, carcinoma and leukemia cells to natural killer (NK) cell cytotoxicity. Tumor cells were treated with leukoregulin for 1 h at 37 degrees C and tested for sensitivity to NK and LAK cytotoxicity in a 4-h chromium-release assay. NK-resistant Daudi, QGU and C4-1 human cervical carcinoma cells became sensitive to NK cytotoxicity after leukoregulin treatment, and their sensitivity to LAK was increased two- to sixfold. Y-79 retinoblastoma cells, which are moderately sensitive to NK and very sensitive to LAK, became increasingly sensitive (two- to four-fold) to both NK and LAK cell cytotoxicity. Recombinant granulocyte-macrophage colony-stimulating factor (GM-CSF), recombinant interleukin-1 (alpha and beta), recombinant interferon gamma, recombinant tumor necrosis factor or combinations of the latter two failed to up-regulate tumor cell sensitivity to NK and LAK cell cytotoxicity. However, treatment with recombinant interferon gamma for 16-18 h, GM-CSF and interleukin-1 beta for 1 h induced a state of target cell resistance to both NK and LAK cell cytotoxicity. Leukoregulin may have an important physiological function in modulating NK and LAK cell cytotoxicity by increasing the sensitivity of target cells to these natural cellular immunocytotoxicity mechanisms.     

Invariant natural killer T cells from rhesus macaque spleen and peripheral blood are phenotypically and functionally distinct populations

BACKGROUND: Natural killer T cells (NKT) possess dual functions of innate and adaptive immune systems, controlling viral infections and regulating autoimmune diseases. Non-human primates (NHP) are penultimate models for advancing therapeutic immunoregulatory strategies for translational application in humans, though, little is known about NHP NKT cells. Here we characterized rhesus macaque NKT cells ex vivo. METHODS: The frequency, phenotype and intracellular cytokine production of V alpha 24+ 6B11+ invariant NKT (iNKT) cells were analyzed by multi-color flow cytometry. V alpha 24J alpha Q mRNA expression was analyzed by real-time RT-PCR. RESULTS: The frequencies of peripheral blood (PB) and spleen V alpha 24+ 6B11+ iNKT cells were not significantly different. The iNKT cell subset in spleen was significantly increased for CD4+ CD8+ and CD3+ CD56+ co-expression as well as intracellular interleukin-4 production, which was rarely observed in circulating PB. CONCLUSION: Spleen iNKT cells in rhesus macaques are Th2 biased and display phenotypically and functionally distinct profiles from their PB counterpart.