Peritoneal NK Research Articles

Protective Effect of NK1.1+T Cells as Well as NK Cells against Intraperitoneal Tumors in Mice

Peritoneal resident cells of mice normally contain small populations of NK cells and NK1.1+αβT cells. These populations increased after either 3LL or EL4 tumor inoculations into the peritoneal cavity.In vivodepletion of NK cell alone by anti-asialo GM1 (ASGM1) Ab significantly decreased survival time of tumor-injected mice, while depletion of both NK cells and NK1.1+T cells by anti-NK 1.1 Ab greatly shortened mouse survival time. NK1.1+T cells in peritoneal cavity consist of a larger proportion of double-negative T cells and smaller populations of CD4+T cells and Vβ8+T cells compared with liver NK1.1+T cells and normally lack Vβ2+T cells. Tumor inoculation induced rapid IL-12 and IFN-γ mRNA in tumor-infiltrating mononuclear cells (TIM). Although anti-NK1 Ab pretreatmentin vivoabrogated IFN-γ mRNA expression and IFN-γ production of TIM, NK cell depletion alone by anti-ASGM1 Ab pretreatment retained IFN-γ mRNA expression and partly inhibited IFN-γ production of TIM. Peritoneal NK cells as well as NK1.1+T cells but not NK1.1−T cells of 3LL cell- or EL4 cell-injected mice showed cytotoxicities against the same tumor cells. Further, either anti-IL-12 Ab or anti-IFN-γ Ab ip injection significantly shortened EL4 cell-inoculated mouse survival time. Our findings suggest that peritoneal macrophages activated by tumors produce IL-12 which activates NK cells and NK1.1+T cells to produce IFN-γ and both NK cells and NK1.1+T cells are important in suppressing the growth of the intraperitoneal tumors.

THE GALACTOSIDE-SPECIFIC LECTIN FROM MISTLETOE AS BIOLOGICAL RESPONSE MODIFIER

Experience with herbal extracts can guide the isolation of substances that effectively amend aspects of the host's defence system against tumor growth and spread. This capacity appears to be conferred to mistletoe (Viscum album) extract by a rather small dose range of the galactoside-specific lectin (VAA). It is a biochemically characterized dimer, consisting of a toxic subunit that acts as a RNA N-glycosidase (depurination of A-4324 in 28S rRNA) and a carbohydrate-binding B-chain. The binding of this subunit to galactose-exposing glycoligands on mononuclear cells elicits cytokine secretion in vitro and antitumoral/antimetastatic capacity in vivo in lymphosarcoma/sarcoma model systems. Increases in NK cell number, the activity of peritoneal macrophages and NK cells as well as the response of splenic T cells to mitogens are detectable. Immunophenotyping of blood samples from lectin-treated patients reveals increases in the number of helper/inducer T cells, NK cells and CD25-positive cells. Since the response to the treatment is assumed to be dependent on the presence of lectin-specific ligands on inflammatory host cells, histopathological monitoring of tumor specimens with labelled lectin is conceivable to be one factor of relevance to predict a response to the treatment in animal models or within clinical trials.

Trafficking and activation of murine natural killer cells: Differing roles for IFN-γ and IL-2

The repeated ip injection of highly purified recombinant IFN-γ or IL-2 resulted in a local increase in peritoneal NK activity. This increase in lytic activity was paralleled by increases in the number of peritoneal leukocytes reacting with a rat monoclonal antibody directed against the NK cell-associated surface antigen LGL-1. LGL-1 reacts specifically with the majority of murine NK cells in BALB/c and C57BL/6 mice. A single injection of IFN-γ induced more peritoneal NK activity at 24 hr than IL-2 on a protein basis. Both cytokines induced increases in the number of LGL-1 + peritoneal cells by 24 hr after injection. Simultaneous injection of suboptimal amounts of IFN-γ (100 U) and IL-2 (10,000 U) resulted in a significant augmentation of peritoneal NK activity over that observed with either cytokine alone. Also, the peritoneal NK activity generated in response to ip injection of high doses of IL-2 (100,000 U) could be dramatically reduced by simultaneous injection of a neutralizing monoclonal antibody to IFN-γ. Administration of IFN-γ 1 day prior to IL-2 resulted in a significant augmentation of the NK activity above that observed with the individual cytokines. In contrast, injection of IL-2 prior to IFN-γ did not enhance NK activity over that observed with the individual cytokines. Both cytokines must be injected ip for the complementary effects of IFN-γ and IL-2 on peritoneal NK activity to occur. In contrast, in vitro incubation of peritoneal leukocytes with IFN-γ resulted in neither a significant enhancement of NK lytic activity nor an increase in the number of LGL-1 + cells. In vitro treatment of peritoneal leukocytes with IL-2 always resulted in significant augmentation of NK lytic activity in the absence of any increase in the number of LGL-1 + cells. These data are consistent with the hypothesis that the local release of IFN-γ increases peritoneal NK activity by promoting the influx of blood-borne LGL-1 + NK cells from other sites. In contrast, low doses of IL-2 augment the lytic activity of local resident NK cells, whereas high doses of this cytokine induce both an activation of local NK cells and emigration of LGL-1 + NK cells from other sites due to the endogenous generation of IFN-γ within the peritoneal cavity. Therefore, the local release of IFN-γ may play an important role in regulating NK cell infiltration in vivo.

Antitumor and immunologic effects of a pyridine-extracted fraction of Propionibacterium acnes.

The antitumor and immunological effects of a pyridine extractable fraction of Propionibacterium acnes were tested in a murine ovarian teratocarcinoma (MOT) model. Previous studies have demonstrated that tumor rejection in this model depends upon sequential activation of tumoricidal neutrophils (PMNs) followed by cytostatic macrophages. The pyridine extract significantly prolonged the survival of mice challenged with 10(3) or 10(4) MOT cells but had little impact on a 10(5) tumor inoculum. In vivo cytoreduction occurred within the first 24 h following IP treatment which correlated temporally with the influx of tumoricidal PMNs into the peritoneal cavity. Immunotherapy failure in mice challenged with 10(5) MOT cells occurred between 48 and 72 h after treatment when macrophage chemotaxis into the peritoneal cavity was initiated. Although injection of unfractionated bacteria activated MOT-cytostatic macrophages, the pyridine extract was deficient in this regard. Intraperitoneal injection of the pyridine extract resulted in an early (day +1) depression and late (day +5) enhancement of peritoneal NK cytotoxicity. These data suggest that the retention of neutrophil-activating moieties in the pyridine extract are sufficient for antitumor effects against low tumor inocula while the depletion of macrophage-activating determinants results in diminished effects against larger tumor cell challenges.