A new human pancreatic carcinoma cell line developed for adoptive immunotherapy studies with lymphokine-activated killer cells in nude mice

Summary A human tumor cell line designated SU.86 has been established from a moderate-to-poorly differentiated pancreatic carcinoma of ductal origin specifically for adoptive immunotherapy studies. This line was characterized as to its ability to be lysed in vitro by autologous and allogeneic lymphokine-activated killer (LAK) and natural killer cells and to grow in nude mice. SU.86 has been growing continuously in cell culture for more than 100 passages since 22 September 1986. Transplantation orthotopically and heterotopically into athymic Swiss nude mice showed that tumor take was 100% in the orthotopic position when young (4 to 6 wk old) mice were used and 0% when adult (8 wk old) mice were used (P=0.004). In the heterotopic position (subcutaneous), tumor take was 100% in neonate (2 to 3 wk old) and young mice and 50% in adults. The rate of tumor growth was inversely correlated with age (P<0.001). The histologic pattern is similar to that observed in most human pancreatic carcinomas with pseudoglandular structures and frequent mitotic figures. SU.86 has a doubling time of 77 h in vitro and produces carcinoembryonic antigen, 594 ng/10⁶ cells in 3 d. Chromosomal analysis shows heterogeneity with two notable cell subpopulations. The cell line is moderately sensitive to lysis by LAK cells in a standard, 4-h chromium-51 release assay (35.4±4.0%). When grown together with LAK cells in vitro, it is lysed completely in culture in 8 to 15 d, depending on the serum concentration.     

Growth of MCF-7 human breast carcinoma in severe combined immunodeficient mice: Growth suppression by recombinant interleukin-2 treatment and role of lymphokine-activated killer cells

Summary The severe combined immunodeficient (SCID) mouse, lacking functional T and B lymphocytes, has been considered by many groups to be a prime candidate for the reconstitution of a human immune system in a laboratory animal. In addition, this immuno-deficient animal would appear to have excellent potential as a host for transplanted human cancers, thus providing an exceptional opportunity for the study of interactions between the human immune system and human cancer in a laboratory animal. However, because this animal model is very recent, few studies have been reported documenting the capability of these mice to accept human cancers, and whether or not the residual immune cells in these mice (e.g. natural killer, NK, cells; macrophages) possess antitumor activities toward human cancers. Thus, the purpose of this study was (a) to determine whether or not a human breast carcinoma cell line (MCF-7) can be successfully transplanted to SCID mice, (b) to determine whether or not chronic treatment of SCID mice with a potent lymphokine (recombinant interleukin-2, rIL-2) could alter MCF-7 carcinoma growth, and (c) to assess whether or not rIL-2-activated NK cells (LAK cells) are important modulators of growth of MCF-7 cells in SCID mice. To fulfill these objectives, female SCID mice were implanted s.c. with MCF-7 cells (5 × 10⁶ cells/mouse) at 6 weeks of age. Six weeks later, some of the mice were injected i.p. twice weekly with rIL-2 (1 × 10⁴ U mouse^–1 injection^–1). Results clearly show that MCF-7 cells can grow progressively in SCID mice; 100% of the SCID mice implanted with MCF-7 cells developed palpable measurable tumors within 5–6 weeks after tumor cell inoculation. In addition, MCF-7 tumor growth was significantly (P <0.01) suppressed by rIL-2 treatment. rIL-2 treatment was non-toxic and no effect of treatment on body weight gains was observed. For non-tumor-bearing SCID mice, splenocytes treated in vitro with rIL-2 (lymphokine-activated killer, LAK, cells) or splenocytes derived from rIL-2-treated SCID mice (LAK cells) had significant (P <0.01) cytolytic activity toward MCF-7 carcinoma cells in vitro. In contrast, splenocytes (LAK cells) derived from tumor(MCF-7)-bearing rIL-2-treated SCID mice lacked cytolytic activities toward MCF-7 cells in vitro. No significant concentration of LAK cells in MCF-7 human breast carcinomas was observed nor did rIL-2 treatment significantly alter growth of MCF-7 cells in vitro. Thus, while rIL-2 treatment significantly suppressed growth of MCF-7 breast carcinomas in SCID mice, the mechanism of this growth suppression, albeit clearly not involving T and B lymphocytes, does not appear to be mediated via a direct cytolytic activity of LAK cells toward the carcinoma cells. However, rIL-2-activated SCID mouse splenocytes (LAK cells) do possess the capability of significant cytolytic activity toward MCF-7 human breast carcinoma cells. Thus, treatment of SCID mice with a potent lymphokine (rIL-2) induces a significant antitumor host response, a response that does not involve T and B lymphocytes and appears not to involve NK/LAK cells. This host response must be considered in future studies designed to investigate the interactions of reconstituted human immune systems and human cancers within this highly promising immuno deficient experimental animal model.     

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.     

Lasting effects of an impairment of Th1-like immune response in γ-irradiated mice: A resemblance between irradiated mice and aged mice

Although one of the several chronic effects of ionizing radiation is aging, there are no experimental data on radiation-induced immunological aging. The most interesting change in aging was a helper T (Th) 1/Th2 imbalance. We investigated chronic effect on immune responses after ionizing radiation and its effects in irradiated mice were compared with those of aged mice. The 2-month-old mice received a whole-body irradiation of 5 Gy. At 6 months after irradiation, we compared the immune functions of the irradiated mice with those of normal mice of the same age and with those of older. Interferon (IFN)-γ and antigen-specific immunoglobulin (Ig)G2a level were lower in the irradiated mice than in normal mice of same age, showing similar levels to those of old normal mice. In contrast, interleukin (IL)-4 and IL-5 and antigen-specific IgG1 level were increased in irradiated mice when compared with the same aged-normal mice. Next, we investigated the low expression of IL-12p70, IL-12 receptors and IL-18 receptors in irradiated and old mice. Also, the decrease of natural killer cell activity was intensified in the irradiated mice, showing lower than values to those of old mice. Interestingly, in irradiated mice, the absolute numbers and the percentages of natural killer (NK) cells was extremely decreased. But the absolute numbers of Th cells and cytotoxic T (Tc) cells in old mice were significantly decreased. In conclusion, an immunological imbalance by the whole-body irradiation of 5 Gy induces to persist in the long term, resulting in the similar results with aging. Our results suggest that the downregulation of the Th1-like immune response shown in old mice rapidly occurred through exposure of ionizing radiation.     

The influence of protein malnutrition on T cell, natural killer cell, and lymphokine-activated killer cell function, and on biological responsiveness to high-dose interleukin-2

Protein malnutrition is prevalent in cancer patients, however the influence of protein-calorie malnutrition on anti-tumor immune effector mechanisms is unclear. In addition, the effect of malnutrition on host immunological and biological responsiveness to recombinant interleukin-2 (rIL-2) is unknown. In Swiss mice (n = 100), we observed that T cell activation, T cell response to rIL-2, T suppressor cell generation, cytotoxic T lymphocyte development, and the cytolytic activity of LAK cells were not significantly impaired by two or three weeks of feeding with a 2.5% protein diet compared with mice fed an isocaloric diet in which protein calories constituted 24% of the total. In CBA/J mice (n = 100), we observed a significant (P less than 0.05) impairment of poly(I:C)-inducible natural killer cell function in mice ingesting the 2.5% diet. In both A/J (n = 40) and Swiss mice (n = 40), cytotoxic responses after 3 days treatment with rIL-2 (5 X 10(6) U/kg body wt. three times daily) were comparable in both dietary groups. These studies demonstrate that protein depletion is associated with impaired poly (I:C)-induced natural killer cell function in CBA/J mice. However, T cell function and biological responsiveness to high-dose rIL-2 were not significantly impaired.     

Postoperative administration of interleukin-12 significantly enhances the anti-tumor immune response of MBT-2 bladder cancer bearing mice

This study, using the MBT-2 murine bladder tumor model, mainly investigated the role of interleukin-12 (IL-12) in the specific antitumor immune response of a tumor-bearing host when systemically administrated after surgery. Day 17 tumor-bearing mice (D17TBM) along with non-tumor bearing naive mice were treated with daily intraperitoneal (i.p.) injection of IL-12 (0.25 microg/mouse) from day 18 to day 24 for a total of 7 doses. Their splenocytes were obtained on Day 31 for natural killer cells (NK), lymphokine activated killer cells (LAK) and cytotoxic T lymphocyte (CTL) activity assay and lymphocyte subsets phenotypic analysis. The tumor suppression effect of systemic IL-12 administration was evaluated based on the tumor outgrowth of the higher number of tumor cells rechallenged 24 hours after resectioning of the primary tumor. After evaluation on Day 31, the result of in vitro cytotoxicity assay revealed that systemic administration of IL-12 mainly enhanced the splenic LAK and CTL activities in non-tumor-primed naive mice, and the NK activity in tumor-primed D17TBM, respectively. However, in vivo administration of IL-12 with or without IL-2 failed to upgrade the proportions of either CD4+ CD44+ or CD8+ CD44+ T cells subsets in the spleens and regional inguinal lymph nodes (LNs) of both the D17TBM and naive mice. However, the splenic CD8+ CD44+ T-cell subset in the IL-12-treated D17TBM increased prominently after further culturing in the presence of IL-2 400 units/ml plus IL-12 25 ng/ml for 4 days. The fact that systemic administration of IL-12 significantly suppressed the outgrowth of Day-18 challenged tumor cells, especially in D17TBM, clearly indicates that the established specific antitumor immunity in tumor-primed D17TBM was efficiently augmented. From the results of this study, we conclude that, after surgical resection of a primary tumor, systemic administration of IL-12 can be an effective adjuvant therapy because it demonstrates a significant augmentation effect on the tumor-specific immune response in the tumor-primed host.     

NK and NKT cell functions in immunosenescence

Immunosenescence is defined as the state of dysregulated immune function that contributes to the increased susceptibility to infection, cancer and autoimmune diseases observed in old organisms, including humans. However, dysregulations in the immune functions are normally counterbalanced by continuous adaptation of the body to the deteriorations that occur over time. These adaptive changes are likely to occur in healthy human centenarians. Both innate (natural) and adaptive (acquired) immune responses decline with advancing age. Natural killer (NK) and natural killer T (NKT) cells represent the best model to describe innate and adaptive immune response in aging. NK and NKT cell cytotoxicity decreases in aging as well as interferon-gamma (IFN-gamma) production by both activated cell types. Their innate and acquired immune responses are preserved in very old age. However, NKT cells bearing T-cell receptor (TCR) gammadelta also display an increased cytotoxicity and IFN-gamma production in very old age. This fact suggests that NKT cells bearing TCRgammadelta are more involved in maintaining innate and adaptive immune response in aging leading to successful aging. The role played by the neuroendocrine-immune network and by nutritional factors, such as zinc, in maintaining NK and NKT cell functions in aging is discussed.     

IL－2／LAK对荷瘤机体细胞免疫功能的改善

本实验将ＩＬ－２／ＬＡＫ应用于荷瘤鼠,对荷瘤机体的细胞免疫功能（鼠脾ＮＫ细胞活性、鼠脾ＩＬ－２产生能力及腹腔巨噬细胞吞噬功能）进行动态观察。结果证实：ＩＬ－２／ＬＡＫ能在一定程度上改善荷瘤机体的细胞免疫功能,并能够有一定程度的阻抑荷瘤机体的细胞免疫功能降低。同时探讨了ＩＬ－２／ＬＡＫ在肿瘤治疗中,提高细胞功能的机理。     

Prostaglandin E2-mediated suppression of murine lymphokine-activated killer cell activity generated from tumor-bearing hosts by interferon-gamma

The effect of mouse recombinant interferon-gamma (IFN-gamma) on murine lymphokine-activated killer (LAK) cell activity was investigated using a natural killer-resistant, LAK-sensitive, spontaneously developed, weakly immunogenic, syngeneic murine mammary adenocarcinoma, a tumor model mimicking that of human disease. When all of the splenocytes prepared from tumor-bearing mice were cultured with recombinant interleukin-2 (IL-2) and IFN-gamma, LAK cell activity was suppressed in an IFN-gamma dose-dependent manner. An increase in the prostaglandin E2 (PGE2) content in the corresponding culture media was detected, as was IFN-gamma dose dependent. The suppression of generation of LAK cell activity by IFN-gamma was abrogated, accompanied by the elimination of the increase in PGE2 content, when plastic dish and nylon wool-treated nonadherent macrophage-depleted splenocytes were used. These results indicated that IL-2-induced LAK cell activity generated from the splenocytes of tumor-bearing mice was suppressed by IFN-gamma, and that PGE2 secreted from the macrophages of the splenocyte cultures served as the mediator in this IFN-gamma dose-dependent suppression of IL-2-induced LAK cell activity.     

Natural killer (NK) and lymphokine-activated killer (LAK) cell functions from healthy dogs and 29 dogs with a variety of spontaneous neoplasms

To investigate natural killer (NK) and lymphokine-activated killer (LAK) cell functions from 10 healthy dogs and 29 dogs with a variety of spontaneous neoplasms, large granular lymphocytes (LGLs) from blood samples were separated by a 58.5% Percoll density gradient. LGLs were stimulated with a low dose of recombinant human interleukin 2 (rhIL-2) for 7 days. Cytotoxicity of effector cells against the susceptible CTAC cell line was measured before and after stimulation. Compared with those before stimulation, the percentage of LGLs after stimulation with rhIL-2 was found to be significantly increased (P<0.01) in both dogs with tumors and controls. However, the increase was significantly higher in control animals, indicating a defect in proliferation ability of NK cells in canine tumor patients. After stimulation with rhIL-2, lymphokine-activated killer (LAK) cell activity in dogs with tumors was significantly lower (P<0.01) when compared with controls. Reduced cytotoxicity of rhIL-2–activated NK cells in dogs with tumors seems to be attributable to the presence of a diminished proliferative capacity of NK cells and a decreased ability of LAK cells to lyse target cells. Further knowledge of the precise function of IL-2–activated NK cells in dogs with tumors may help to optimize new and therapeutically beneficial treatment strategies in canine and human cancer patients. Our findings suggest that the dog could also serve as a relevant large animal model for cancer immunotherapy with IL-2.     

Lymphokine-activated killer cells are rejected in vivo by activated natural killer cells

A 4-h in vivo cytotoxicity assay was used to study the fate of implanted IL-2-generated, lymphokine-activated killer (LAK) cells in mice undergoing an activated NK cell response. 125Iododeoxyuridine-labeled LAK cells were rejected from selected organs of C57BL/6 mice infected with lymphocytic choriomeningitis virus or treated with IL-2 or the IFN inducer poly I:C. This rejection was abrogated by the selective depletion of NK cells with antibodies to asialo-GM1 and NK1.1 Ag. Similar results were noted when LAK cells were generated from the spleens of B and T cell-deficient severe combined immunodeficiency mice and when LAK cells were implanted into severe combined immunodeficiency mice. These data indicate that NK cells activated by virus infections or by IL-2 infusions directly or indirectly eliminate implanted LAK cells. Because LAK cells are used in the treatment of certain human cancers, the strategy of accompanying this therapy with IL-2 infusions should be reassessed in light of these results.     

Partial correction of defective generation of lymphokine-activated killer cells in patients with chronic myelogenous leukaemia after in vivo treatment with interferon-α (wellferon)

Summary Patients with chronic myelogenous leukaemia (CML) in untreated chronic phase are deficient in their ability to generate lymphokine-activated killer (LAK) cells from peripheral blood mononuclear cells although they posses essentially normal levels of CD16⁺ and Leu19⁺ lymphocytes, which do not seem to be actively suppressed by tumour cells. Attempts to enhance LAK cell generation in these patients are reported here. Combining the lymphokines interleukins-2, with -4 and -5 (IL-2, IL-4, IL-5), was not successful; in fact, IL-4 depressed LAK cell induction in both normal donors and CML patients. The phorbol ester 12-O-tetradecanoylphorbol 13-acetate also failed to enhance cytotoxicity of normal donors or patients, and indomethacin was similarly without effect. The only agent found to enhance LAK cell induction by IL-2 in normal donors was interferon- (but not IFN-) and even this modest effect was not seen with the cells of CML patients. Increasing concentrations of IL-2 and/or culture duration also failed to improve LAK cell generation by patients. The only improvement in LAK cell generation was observed in CML patients treated for one or more months with IFN-, where a steady increase of LAK activity with time after initiation of therapy was noted. These results show that the blockade of LAK cell induction in chronic-phase myelogenous leukaemia patients is difficult to lift pharmacologically in vitro but possibly susceptible to biological response modifiers in vivo.     

Disrupting Immune Regulation Incurs Transient Costs in Male Reproductive Function

Background

Immune protection against pathogenic organisms has been shown to incur costs. Previous studies investigating the cost of immunity have mostly focused on the metabolic requirements of immune maintenance and activation. In addition to these metabolic costs, the immune system can induce damage to the host if the immune response is mis-targeted or over-expressed. Given its non-specific nature, an over-expressed inflammatory response is often associated with substantial damage for the host. Here, we investigated the cost of an over-expressed inflammatory response in the reproductive function of male mice.

Methodology/Principal Findings

We experimentally blocked the receptors of an anti-inflammatory cytokine (IL-10) in male mice exposed to a mild inflammatory challenge, with each treatment having an appropriate control group. The experiment was conducted on two age classes, young (3 month old) and old (15 month old) mice, to assess any age-related difference in the cost of a disrupted immune regulation. We found that the concomitant exposure to an inflammatory insult and the blockade of IL-10 induced a reduction in testis mass, compared to the three other groups. The frequency of abnormal sperm morphology was also higher in the group of mice exposed to the inflammatory challenge but did not depend on the blockade of the IL-10.

Conclusions

Our results provide evidence that immune regulation confers protection against the risk of inflammation-induced infertility during infection. They also suggest that disruption of the effectors involved in the regulation of the inflammatory response can have serious fitness consequences even under mild inflammatory insult and benign environmental conditions.     

Delineating the relationship between immune system aging and myogenesis in muscle repair

Recruited immune cells play a critical role in muscle repair, in part by interacting with local stem cell populations to regulate muscle regeneration. How aging affects their communication during myogenesis is unclear. Here, we investigate how aging impacts the cellular function of these two cell types after muscle injury during normal aging or after immune rejuvenation using a young to old (Y‐O) or old to old (O‐O) bone marrow (BM) transplant model. We found that skeletal muscle from old mice (20 months) exhibited elevated basal inflammation and possessed fewer satellite cells compared with young mice (3 months). After cardiotoxin muscle injury (CTX), old mice exhibited a blunted inflammatory response compared with young mice and enhanced M2 macrophage recruitment and IL‐10 expression. Temporal immune and cytokine responses of old mice were partially restored to a young phenotype following reconstitution with young cells (Y‐O chimeras). Improved immune responses in Y‐O chimeras were associated with greater satellite cell proliferation compared with O‐O chimeras. To identify how immune cell aging affects myoblast function, conditioned media (CM) from activated young or old macrophages was applied to cultured C2C12 myoblasts. CM from young macrophages inhibited myogenesis while CM from old macrophages reduced proliferation. These functional differences coincided with age‐related differences in macrophage cytokine expression. Together, this study examines the infiltration and proliferation of immune cells and satellite cells after injury in the context of aging and, using BM chimeras, demonstrates that young immune cells retain cell autonomy in an old host to increase satellite cell proliferation.     

Multiple MyD88-dependent responses contribute to pulmonary clearance of Legionella pneumophila

MyD88-dependent signalling is important for secretion of early inflammatory cytokines and host protection in response to Legionella pneumophila infection. Although toll-like receptor (TLR)2 contributes to MyD88-dependent clearance of L. pneumophila , TLR-independent functions of MyD88 could also be important. To determine why MyD88 is critical for host protection to L. pneumophila , the contribution of multiple TLRs and IL-18 receptor (IL-18R)-dependent interferon-gamma (IFN-γ) production in a mouse was examined. Mice deficient for TLR5 or TLR9, or deficient for TLR2 along with either TLR5 or TLR9, were competent for controlling bacterial replication and had no apparent defects in cytokine production compared with control mice. MyD88-dependent production of IFN-γ in the lung was mediated primarily by natural killer cells and required IL-18R signalling. Reducing IFN-γ levels did not greatly affect the kinetics of L. pneumophila replication or clearance in infected mice. Additionally, IFN-γ-deficient mice did not have a susceptibility phenotype as severe as the MyD88-deficient mice and were able to control a pulmonary infection by L. pneumophila . Thus, MyD88-dependent innate immune responses induced by L. pneumophila involve both TLR-dependent responses and IL-18R-dependent production of IFN-γ by natural killer cells, and these MyD88-dependent pathways can function independently to provide host protection against an intracellular pathogen.     

Interleukin-6 does not support interleukin-2 induced generation of human lymphokine-activated killer cells

Summary The activity of lymphokine-activated killer (LAK) cells is supported by various cytokines. The objective of this study was to see if recombinant interleukin-6 (IL-6) either alone or in combination with interleukin-2 (IL-2) has any effect on the generation of LAK cells. Peripheral blood mononuclear cells of healthy donors were cultured for 4 or 6 days with both cytokines either alone or in combination. LAK activity against K562 and natural killer-resistant Daudi cells was assessed by a 4-h and an 18-h⁵¹Cr-release assay at various effector to target ratios. IL-6 alone in increasing concentrations did not induce LAK cell activity. Neither additive nor synergistic effects of IL-6 with IL-2 were observed. Immunofluorescence analysis with phycoerythrin-conjugated anti-CD56 antibody demonstrated that IL-6 could not maintain or increase the number of CD56-positive cells over a 6-day culture period. These results suggest that IL-6 does not support LAK cell generation by itself or increase LAK cell activity in combination with IL-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.     

Role of proliferation in LAK cell development

Summary Lymphokine-activated killer (LAK) cell activity may be largely the result of activation and/or expansion of peripheral blood natural killer cells by culture with interleukin-2 (IL-2). We have examined the role of proliferation in LAK cell development by either inhibiting or enhancing the proliferative potential of peripheral blood lymphocytes. Inhibition of proliferation was accomplished using irradiation, mitomycin C, or the iron chelator deferoxamine. For each of these agents, a dose-dependent inhibition of proliferation was observed. At doses of inhibitor which nearly completely blocked thymidine uptake, the development of LAK activity was only partially impaired. The mitogenic lectins phytohemagglutinin (PHA) and concanavalin A (Con A) augmented the proliferative response of peripheral blood lymphocytes to IL-2. However, augmentation by PHA, but not Con A, consistently resulted in a decrease in LAK activity. This inhibition of LAK activity by PHA did not appear to be due to inhibition of the effector cell, nor to preferential expansion of irrelevant cells. These data suggests that not all LAK activity is dependent on proliferation, and that high levels of proliferation in the presence of IL-2 do not necessarily lead to LAK activity.This work was supported in part by U.S. Public Health Service Grant CA-34442 (S. H. G.) and pre-doctoral training grant CA-09120 (F. J. R.)     

Live Attenuated Leishmania donovani Centrin Knock Out Parasites Generate Non-inferior Protective Immune Response in Aged Mice against Visceral Leishmaniasis

BackgroundVisceral leishmaniasis (VL) caused by the protozoan parasite Leishmania donovani causes severe disease. Age appears to be critical in determining the clinical outcome of VL and at present there is no effective vaccine available against VL for any age group. Previously, we showed that genetically modified live attenuated L. donovani parasites (LdCen-/-) induced a strong protective innate and adaptive immune response in young mice. In this study we analyzed LdCen-/- parasite mediated modulation of innate and adaptive immune response in aged mice (18 months) and compared to young (2 months) mice.MethodologyAnalysis of innate immune response in bone marrow derived dendritic cells (BMDCs) from both young and aged mice upon infection with LdCen-/- parasites, showed significant enhancement of innate effector responses, which consequently augmented CD4⁺ Th1 cell effector function compared to LdWT infected BMDCs in vitro. Similarly, parasitized splenic dendritic cells from LdCen-/- infected young and aged mice also revealed induction of proinflammatory cytokines (IL-12, IL-6, IFN-γ and TNF) and subsequent down regulation of anti-inflammatory cytokine (IL-10) genes compared to LdWT infected mice. We also evaluated in vivo protection of the LdCen-/- immunized young and aged mice against virulent L. donovani challenge. Immunization with LdCen-/- induced higher IgG2a antibodies, lymphoproliferative response, pro- and anti-inflammatory cytokine responses and stimulated splenocytes for heightened leishmanicidal activity associated with nitric oxide production in young and aged mice. Furthermore, upon virulent L. donovani challenge, LdCen-/- immunized mice from both age groups displayed multifunctional Th1-type CD4 and cytotoxic CD8 T cells correlating to a significantly reduced parasite burden in the spleen and liver compared to naïve mice. It is interesting to note that even though there was no difference in the LdCen-/- induced innate response in dendritic cells between aged and young mice; the adaptive response specifically in terms of T cell and B cell activation in aged animals was reduced compared to young mice which correlated with less protection in old mice compared to young mice.ConclusionsTaken together, LdCen-/- immunization induced a significant but diminished host protective response in aged mice after challenge with virulent L. donovani parasites compared to young mice.