Characterization of functional surface structures on human natural killer cells

Does graft-versus-host disease attack epithelial stem cells?

Graft-versus-host disease (GvHD) is the opposite of graft rejection in that a transplant containing donor lymphocytes attacks the host's skin, liver and gut. This disease can usefully also attack host tumor cells. There is a peculiar distribution of normal tissue targets in epithelial stem cell sites, suggesting that GvHD may be the abnormal counterpart of a physiological growth control system. Efforts to understand how the graft-versus-tumor effect could be therapeutically separated from GvHD require further understanding of the mechanisms involved in GvHD.

Fc gamma-receptor III (CD 16) is involved in NK-B cell interaction

CD16, the low affinity receptor for monomeric IgG (Fc gamma RIIIA), is a well characterized activation molecule on NK cells. In this study we investigated the role of CD16 in NK cell-mediated regulation of immunoglobulin production. Cocultures of the CD16+ human NK clone CNK6 and highly purified SAC/IL-2-activated B lymphocytes with various CD16 antibodies showed significantly diminished NK-enhanced immunoglobulin production in a dose-dependent manner, indicating that CD16 is relevant in NK-B cell interaction. Similarly, recombinant soluble CD16 incubated with B cells before cultures, suppressed the NK cell-stimulated B cell antibody response. Enhanced immunoglobulin production was also inhibited by Fc-specific F(ab')2 anti-body fragments. Coculture of NK cells with B lymphocytes resulted in induction of mRNA for IFN-gamma and TNF-alpha. The accumulation of mRNA for these cytokines was prevented by addition of CD16 and Fc-specific antibodies. It is proposed that interaction of CD16 on NK cells with B cell bound immunoglobulin leads to induction of cytokines in NK cells which stimulate immunoglobulin production by B cells.

CD3 delta and epsilon gene expression in CD3-CD16+ natural killer cell clones derived from thymic precursors

To better understand the maturational stages during T-cell development, we studied the expression of CD3 delta and CD3 epsilon genes, as well as the presence of TCR gene rearrangements, within CD3-CD16+ NK clones derived from thymic precursors in vitro. Northern blot analysis revealed that CD3-CD16+ clones derived from CD7+CD3-CD4-CD8- (TN) thymocytes expressed transcripts for the CD3 epsilon gene; however, no transcripts for the CD3 delta gene were detected. Importantly, both the CD3 epsilon and CD3 delta genes were expressed in TN thymocytes examined prior to cloning. A CD7+CD8+CD3-CD4- thymocyte population that makes up only 0.4% of the total thymocyte pool was also isolated from human thymus. We determined the maturation potential of this CD7+CD8+CD3-CD4- population by limiting dilution cloning and found that 67% of the clones generated in vitro had a CD3-CD16+CD8+ phenotype. In contrast to the NK clones derived from TN precursors, most CD3-CD16+ clones derived from CD7+CD8+CD3-CD4- thymocytes expressed transcripts for both CD3 epsilon and CD3 delta genes. Southern blot analysis of the NK clones derived from either thymic precursor population revealed no rearrangement of the TCR beta or gamma genes. These results demonstrate that the TN progenitor population and their CD3-CD16+ progeny differ in their expression of the CD3 delta transcript and during in vitro culture there is loss of CD3 delta expression and acquisition of surface CD16 within these NK clones. Furthermore, the CD3-CD16+ clones derived from TN versus CD7+CD8+CD3-CD4- thymocytes differed in their expression of the CD3 delta gene. The signaling events regulating the expression of the CD3 invariant chain genes within immature lymphoid progenitor cells may be important in determining their eventual maturation into T-cell and NK-cell lineages in vivo.

Evidence of a selective depletion of a CD16+ CD56+ CD8+ natural killer cell subset during HIV infection

Three-color flow cytometric analysis of CD16+ natural killer (NK) cells was assessed in HIV seropositive patients and healthy heterosexual controls. A selective depletion of lymphocytes with the CD16+ NK phenotype was found among the HIV+ infected patients. When the CD16 lymphocyte subset was further evaluated by three-color flow cytometry, cells bearing both the CD8 and CD56 antigens were significantly decreased. Analysis of activation antigens revealed a large proportion of CD16+ NK cells from HIV+ patients expressed HLA-DR, but this did not correlate with CD25 (IL-2 receptor) expression. The overall loss of the CD8 and CD56 antigens among the NK population with an increase in activation status may be due to differential loss of the NK cell subsets or, alternatively, to the loss of immunoregulatory cytokines, which have been shown to be important in maintaining NK activity. Whether these changes in the NK compartment may influence the outcome of individuals with HIV disease still remains an open question but is an important issue when performing phenotypic analysis of HIV+ subjects.

Characterization of avian natural killer cells and their intracellular CD3 protein complex

Natural killer (NK) cell activity appears to be conserved throughout vertebrate development but NK cells have only been well characterized in mammals. Candidate NK cells have been identified in the chicken as cytoplasmic CD3+ and surface T cell receptor (TCR)/CD3- (TCRO) lymphocytes that often express CD8. The fact that the TCRO cells are abundant in the embryonic spleen before T cells enter this organ allowed us to cultivate the embryonic TCRO cells using growth factors derived from activated adult lymphocytes. These TCRO cells were cytotoxic for an NK target cell line. They expressed cell surface CD8, a putative interleukin-2 receptor, CD45 and a receptor for IgG, but did not express CD4, major histocompatibility complex class II or immunoglobulin. Biochemical analysis of the cytoplasmic CD3 antigen revealed two of the three CD3 gamma, delta and epsilon homologues, and RNA transcripts for the third. The CD3 monoclonal antibody also precipitated a 32-kDa dimer that may represent a heterodimer of different CD3 constituents. TCR alpha and beta gene transcripts were not detected in the TCRO cells. These results indicate that the avian TCRO cell is the mammalian NK cell homologue. The shared evolutionary features of T cells and NK cells in birds and mammals support the idea that they derive from a common progenitor.

Immunoelectron microscopic observations on Leu-7 positive cells in virus-related chronic liver diseases

We investigated the liver biopsies of 78 patients with hepatitis virus-related chronic liver diseases (B type; 14 patients, C type; 64 patients) by immunoelectron microscopy with the Leu-7 monoclonal antibody in order to determine the association of NK/K cells in virus-related chronic liver diseases. Most Leu-7 positive cells in the liver had the Pit cell morphology but a few Pit cells were Leu-7 negative. A few Leu-7 positive cells had neither Pit cell nor typical T cell morphology. No ultrastructural difference was observed in Leu-7 positive cells between hepatitis B virus- and hepatitis C virus-related chronic liver diseases. Regardless of virus type and hepatitis activity, the fine morphology of extravascular Leu-7 positive cells differed considerably from intravascular cells. Leu-7 positive cells were regularly seen in the cellular infiltrates but the ratio of Leu-7 positive cells/whole infiltrates was low. There was no correlation between the inflammatory activity of the disease and the level of Leu-7 positive cell infiltration. A virus aetiology (hepatitis-C or hepatitis-B) did not affect Leu-7 positive cell infiltration. We conclude that NK cells play only a small role in the pathogenesis of hepatitis B virus or hepatitis C virus-related hepatocytolysis, during the chronic stage.

Quantitative measurement of carbohydrate binding activity of mouse macrophage lectin

A simple ELISA assay measuring lectin activity of a mouse macrophage galactose/N-acetylgalactosamine-specific C-type lectin (MMGL) was developed. The binding of galactosylated poly-lysine (termed a ligand) to the immobilized soluble form of MMGL (rML) was measured quantitatively. Consistent with the characteristics of MMGL, the binding was calcium dependent and inhibited by galactose and N-acetylgalactosamine. An antiserum against rML inhibited the ligand binding, demonstrating the usefulness of this method for the screening of blocking antibodies. Using this assay, we found a significant interaction between MMGL and carrageenans, a group of sulfated polygalactans. The inhibitory effect of carrageenans was not attributable to a nonspecific interaction because other types of sulfated polysaccharides, such as glycosaminoglycans and fucoidin, did not interfere with the ligand binding. The relevance of the present finding to the biological activities of carrageenans is discussed.

Role of enhanced cellular adhesion in IL-6-augmented lymphokine-activated killer-cell function

The authors demonstrated previously that a short-term treatment with IL-6 of lymphokine-activated killer (LAK) cells produces an increase in cytotoxic activity of CD56+/CD3- effector cells generated from human PBL as well as from human thymocytes. In the study described here, the mechanisms by which IL-6 enhances LAK cytotoxicity were examined. Like untreated LAK cells, IL-6-treated LAK cells require Ca++ to initiate cytolysis. However, IL-6 treatment of LAK cells does not alter the rate of programming for lysis. Instead, IL-6 increases target-binding capacity of CD56+/CD3- LAK cells in association with the increased cytotoxicity. Similar to target-binding of untreated LAK cells, the binding between IL-6-treated LAK cells and target cells is dependent on Mg++. Cellular adhesion molecules (CAM), CD11a-c, CD18, CD54, CD56, CD58 and CD2 (T11(1) epitope), are up-regulated in LAK cells by culture with IL-2. Among MoAbs to these CAMs, only Abs to CD11a/CD18 (LFA-1) and CD54 (ICAM-1) decrease both target-binding and cytolysis by LAK cells. IL-6 treatment changes neither the proportion nor the intensity of CAM positive cells. However, MoAbs to CD11a/CD18 and CD54 reduce both target-conjugation and cytotoxicity of IL-6-enhanced LAK cells to the same level as control LAK cells treated with the MoAbs. IL-6-enhanced LAK functions (both target-conjugation and target-lysis) are not abrogated by MoAbs to other CAM which do not inhibit standard LAK functions. These results indicate that IL-6 up-regulates cellular events mediated by CD11a/CD18 and CD54 molecules which are involved in standard LAK functions. These events may result in activation of lytic effector cells, associated with an increase in target-binding and an increase in cytotoxicity.

Augmentation of NK activity after oral administration of a traditional Chinese medicine, xiao-chai-hu-tang (shosaiko-to)

We have shown that a traditional Chinese medicine, Xiao-chai-hu-tang (Japanese name: Shosaiko-to) augments natural killer (NK)1 activity in mice. The maximum augmentation of NK activity in the peripheral blood and liver was observed at 12 hr after administration of Shosaiko-to. NK activity was augmented by Shosaiko-to dose-dependently. The augmentation became significantly positive at a dose of 500 mg/kg, and the maximum effect was observed at a dose of 1000 mg/kg. The augmentation of NK activity appeared at first in the liver from 6 hr after administration of Shosaiko-to and became detectable later in the peripheral blood from 12 hr after the administration. Activation of NK cells by Shosaiko-to may occur in the liver and subsequently the activated NK cells may be supplied to the peripheral blood. Changes in percentages of cell surface markers (asialo GM1, CD3, CD4, CD8) after Shosaiko-to treatment were hardly detected, but augmentation of NK activity induced by Shosaiko-to was abrogated by anti-asialo GM1 antibody treatment before the cytotoxicity assay. In addition, cytotoxic activity to P-815 target cells was not detected in Shosaiko-to treated mice. Augmentation of NK activity by Shosaiko-to is probably mediated by functional activation of classical NK cells of asialo GM1+ phenotype. These results suggest that augmentation of NK activity in the liver is one of mechanisms involved in clinical efficacy of Shosaiko-to in patients with virus chronic hepatitis.

Nasal T-cell lymphoma

Nasal T-cell lymphomas represent a controversial subset of malignant lymphomas and include lesions previously termed midline malignant reticulosis, lymphomatoid granulomatosis, and polymorphic reticulosis. Nasal T-cell lymphomas are rare in Western populations and much more prevalent in Asian countries. Clinically, adult males are most often affected. Histologically, an angiocentric infiltrate composed of a spectrum of atypical cells is usually present. Phenotypically, the neoplastic cells lack expression of B-lineage markers, and usually express the T-lineage-associated markers CD2, CD45RO, and CD43; however, they often lack other pan-T-lineage markers. They often express the natural killer marker CD56, but usually lack the natural killer markers CD16 and CD57. Gene rearrangement studies have shown a germline configuration for the antigen receptor genes in the majority of cases. To date, evidence of Epstein-Barr virus has been consistently demonstrated, regardless of the geographic region studied. In situ hybridization studies have localized the Epstein-Barr virus to the atypical cells.

Inhibition of acute, experimental autoimmune encephalomyelitis by the synthetic immunomodulator linomide

Linomide (LS-2616, quinoline-3-carboxamide) is a synthetic immunomodulator that stimulates natural killer cell activity and activates several lymphocytic subpopulations in experimental animals and humans. In this study we determined the effect of oral treatment with linomide on the development of experimental autoimmune encephalomyelitis, an animal model for immune-mediated human demyelinating disorders. Experimental autoimmune encephalomyelitis was induced in SJL/J mice and in an outbred strain of rats (Sabra) by subcutaneous injection of spinal cord homogenate in adjuvant followed by inoculation with Bordetella pertussis. Linomide was administered in drinking water, at an estimated dose of 50 to 100 mg/kg/day. None of the linomide-treated mice (0/41) and Sabra rats (0/15) developed any clinical or pathological signs of experimental autoimmune encephalomyelitis, whereas almost all control animals (48/53 and 18/19, respectively) were severely paralyzed and 64.5% died from the disease. Lymphocytes obtained from linomide-treated animals had reduced in vitro proliferative responses to guinea pig myelin basic protein, proteolipid protein of the myelin, and tuberculin-purified protein derivative, unlike antigen-independent proliferation which was rather unaffected. Natural killer cell activity (tested by a cytotoxic assay on radiolabeled YAC-1 target cells) was significantly enhanced in mice treated with linomide. Our results indicate that modulation of the immune system with linomide leads to complete inhibition of experimental autoimmune encephalomyelitis in the absence of systemic immunosuppression. Linomide could therefore be of use in future clinical trials for the treatment of human autoimmune demyelinating disorders.

Human natural killer cells: a convenient purification procedure and the influence of cryopreservation on cytotoxic activity

The recognition of natural killer cells as a lymphoid subpopulation with a distinct set of surface markers has led to the development of a variety of antibody-based purification methods. In this paper we describe a rapid, three-step negative selection protocol for the purification of human natural killer (NK) cells from the mononuclear cell fraction, which is obtained by the centrifugation of peripheral blood on Ficoll-Paque. Subsequently, monocytes and B lymphocytes are removed by adherence to nylon wool and T lymphocytes by panning with anti-CD3. With this procedure, CD3-, CD16/56+ NK cells are purified about five-fold, from 12 +/- 3% in the starting population to a final purity of 61 +/- 11%. A further increase to > or = 70% is obtained, if an extra Ficoll centrifugation step is included. The recovery of NK cells (50%) is significantly higher than is usually achieved by previously described procedures. Furthermore, we show that activation of cytotoxicity, with concomitant changes in target specificity, occurs when frozen/thawed NK effector cells are kept in culture in order to regain their pre-freezing cytotoxicity levels.

A novel 80-kD cell surface structure identifies human circulating lymphocytes with natural killer activity

Human lymphocytes with natural killer (NK) activity, including most activated gamma/delta+ T lymphocytes, recognize and lyse tumor target cells without requiring recognition of major histocompatibility complex antigen. However, unlike gamma/delta+ T lymphocytes, NK cells do not express CD3/T cell receptor (TCR) molecules, and the receptors involved in cell-mediated cytotoxicity are unknown. To further delineate circulating NK cells, we developed monoclonal antibodies (mAbs) against the human NK leukemia YT2C2. We report the isolation of a mAb termed BY55, recognizing at the cell surface a novel 80-kD protein with restricted expression. In addition to the immunizing cell line, this mAb binds to circulating NK cells, gamma/delta+ cells, and a minor subset of alpha/beta+ T lymphocytes. Expression of the BY55 mAb-reactive epitope/molecule is regulated by activation, as short-term culture of peripheral blood lymphocytes (PBL) with phorbol ester induced its downmodulation. Furthermore, BY55 mAb reactivity was found neither with the NK nor with the TCR alpha/beta+ gamma/delta+ clones tested. Biochemical studies as well as phenotypic analysis revealed that this structure is different from all previously identified molecules on the lymphocyte cell surface. Interestingly, we found that BY55+ cells exert most NK activity obtained with fresh circulating lymphocytes. We report that within fresh E rosette-positive PBL only a subset of the CD16+, CD56+, and CD57+ cells coexpressed BY55 molecule, indicating that BY55 mAb defines a unique subset mediating NK activity of circulating PBL.

Changes in natural immunity during the course of HIV-1 infection

The role of natural killer (NK) and lymphokine-activated killer (LAK) cell-mediated cytotoxicity in AIDS has yet to be established. The objective of this study was to determine inducible LAK cell responses at different stages of HIV-1 infection, and specifically to establish the participation of CD8 lymphocytes in these responses. Peripheral blood lymphocytes (PBL) were isolated from healthy seronegative (CDC-0) subjects and HIV-1+ individuals who were clinically asymptomatic (Centre for Disease Control group 2, CDC-2) or symptomatic (CDC-4) with regard to secondary opportunistic infection (OI). LAK cells were generated upon incubation of PBL with IL-2 and their cytolysis of K562 and U-937 targets was determined using chromium release assays. The role of CD8+ lymphocytes as progenitors and effectors of these LAK cell responses was determined by immunomagnetic depletion of CD8+ cells from precursor PBL and LAK cells, respectively. LAK cell-mediated cytotoxicities in HIV-1-infected individuals were reduced compared with seronegative controls without any corresponding changes in the relative proportions of CD56+ (NK) cells among groups. Depletions of CD8+ subsets from either PBL or LAK cells dramatically reduced total LAK cytotoxic responses and LAK activities per unit CD56+ cell in the OI-/CDC-2 seropositive population. No corresponding changes in LAK activities in seronegative control or HIV+/OI+/CDC-4 groups were observed. Levels of LAK activity against K562 targets in CDC-0/HIV- and CDC-4/HIV+ groups correlated with the percentage of CD56+ LAK cells; corresponding LAK activity in the CDC-2/HIV+ group correlated with the percentage of both CD56+ and CD8+ subsets. These findings suggest that adaptive changes in non-MHC restricted cytotoxic responses occur in HIV-1 individuals at early stages post-HIV infection, before the onset of opportunistic infection.

Infection of natural killer cells by human herpesvirus 6

Natural killer (NK) cells are a functionally defined subset of non-T, non-B lymphocytes of bone marrow origin, which induce lysis of selected target cells, including neoplastic and virus-infected cells. The NK cell function provides an important mechanism of primary defence against viruses in vivo, as demonstrated by the occurrence of multiple herpesvirus infections in patients congenitally lacking NK cells. Here we show that functionally competent CD3- NK clones can be productively infected by human herpesvirus 6 (HHV-6), a T-lymphotropic DNA virus that may play a role in the acquired immunodeficiency syndrome (AIDS) and in the chronic fatigue syndrome, two disorders associated with a defective NK cell activity. The infection is cytopathic and induces de novo expression of CD4, an antigen not expressed within the NK lineage, thereby predisposing NK cells to infection by human immunodeficiency virus type 1 (HIV-1). These results provide evidence that a herpesvirus can directly target and kill NK cells, a potential strategy to suppress the natural anti-viral immunity of the host.

The CD26 antigen is coupled to protein tyrosine phosphorylation and implicated in CD16-mediated lysis in natural killer cells

The levels of CD26 expression, their capacity to induce protein tyrosine phosphorylation and their functional implication in natural killer (NK) cytolysis have been studied. It was found that only a small fraction (12-15%) of peripheral NK cells expresses CD26 compared with the high expression (99%) found in NK clones. The protein tyrosine phosphorylation mediated by means of CD26 activation was studied in NK cells treated with the anti-CD26 MoAb 134-2C2, and two new proteins of 50 and 21 kDa appeared phosphorylated in tyrosine residues. To study the influence of CD26 antigen in NK lysis, we analysed the lytic capacity of NK cells stimulated with different anti-CD26 MoAbs or after separation into CD26+ and CD26- subsets and using K562 as target cells. Under these conditions, no differences were found in the chromium release by the target cells. Redirected lysis through CD16 was also measured by arming the effector cells (CD26+ and CD26-) with anti-CD16 antibody and using K562 as target cells. It was found that CD26- cells showed significantly less CD16-dependent lysis than CD26+ cells. These results indicate that CD26 is related to the CD16-dependent lysis but not to NK cytolysis which may be caused by mediation of protein tyrosine phosphorylation.

Characterization of a novel gene (NKG7) on human chromosome 19 that is expressed in natural killer cells and T cells

NKG7 is a cDNA clone generated from a human NK-cell clone. The DNA and predicted aa sequence of NKG7 is not homologous with any previously reported genes or peptides. NKG7 mRNA is expressed in activated T cells and in A-LAK cells isolated from the peripheral blood of normal individuals, and in normal human kidney, liver, lung and pancreas. Furthermore, NKG7 mRNA is expressed at high levels in TCR gamma delta-expressing CTL clones, and in some TCR alpha beta-expressing CTL clones (both CD4+ and CD8+), but is not expressed in other TCR alpha beta-expressing CTL clones and in cell lines representing B cells, monocytes, and myeloid cells. NKG7 mRNA is not expressed in normal human brain, heart, or skeletal muscle. Southern hybridization of NKG7 suggests that NKG7 is a single-copy gene localized to chromosome 19. A hydropathicity profile of the predicted 148 aa polypeptide indicates that NKG7 is a type-I integral membrane protein with a 38-aa extracellular domain and a 61-aa cytoplasmic domain. These results indicate that the NKG7 gene encodes a novel cell surface protein expressed in several cell types, including NK cells and T cells.

Serotonergic 5-HT1A receptors regulate a cell contact-mediated interaction between natural killer cells and monocytes

Autologous monocytes irreversibly suppressed functions of human natural killer (NK) cells including baseline and lymphokine-induced cytotoxicity, antibody-dependent cellular cytotoxicity (ADCC), and interleukin-2 (IL-2)-induced proliferation. The suppression of these NK-cell functions was cell contact-dependent and could be evoked only by purified monocytes, recovered directly from peripheral blood by countercurrent centrifugal elutriation (CCE). The presence of monocytes also induced the disappearance of CD16 and CD56 antigen on CD3- NK cells (CD3-/16+/56+-->CD3-/16-/56-). By contrast, T-cell proliferation and the expression of CD3 on CD56- T cells were not susceptible to cell contact-mediated suppression by monocytes. The biogenic amine serotonin abrogated monocyte-induced suppression of NK-cell functions as well as down-modulation of CD16/56 NK-cell antigen. Serotonin thus markedly augmented baseline and lymphokine-induced NK-cell cytotoxicity, ADCC, and NK-cell proliferation, and maintained the expression of NK-cell surface antigens in the presence of elutriated monocytes. The effect of serotonin was mediated by 5-HT1A-type serotonin receptors (5-HT1AR) as indicated by mimicry exerted by 5-HT1AR agonists such as 8-OH-DPAT and (+)-ALK, partial antagonism by the 5-HT1AR antagonists pindolol and cyproheptadine, and lack of antagonism by the 5-HT2R antagonist ketanserin or the 5-HT3R antagonist ondansetron. Our data are suggestive of a cell-to-cell-mediated mechanism by which monocytes down-modulate NK-cell function and phenotype and its serotonergic regulation.

Negative modulation of human NK cell activity by purinoceptors. 2. Age-associated, gender-specific partial loss of sensitivity to ATP

Aging is known to modulate the affinity and sensitivity of receptors for hormones and regulatory molecules. We have shown previously that exogenous adenosine triphosphate (ATP), perhaps acting as a purinoceptor agonist, can down-regulate the cell-mediated anti-tumor natural cytotoxic activity of human peripheral blood natural killer (NK) cells. We have extended these studies to investigate whether this effect is modulated during immunosenescence, and if so, whether it is gender-restricted or NK subset-associated. While the inhibitory effect is demonstrable in most individuals, there is a gender-restricted, age-associated transition in the sensitivity of NK cell activity to inhibition by ATP at 2.5 x 10(-5) to 80 x 10(-5) M in vitro. Data from both suboptimal (100 microM) and optimal (800 microM) inhibitory doses of ATP support this conclusion. The ID20ATP were 10.2 x 10(-5) and 17.8 x 10(-5) M for the young (less than 40 years) and elderly (greater than 70 years) females, respectively (P = 0.02). The frequency distribution curve of ATP sensitivity shifts to the left in the elderly, i.e., the sensitivity to be inhibited at 50% or more by ATP was expressed by one-half of young and one-fifth of elderly female donors. Linear regression analysis suggests an inverse relationship between percentage CD57+ and percentage CD16+57+ (but not percentage CD16+) NK subsets and sensitivity to down-regulation by ATP. The mean percentage of the above NK cell phenotypes among lymphocytes from young and old female donors differ significantly (less than 0.0001). The data suggest that the presence of CD57 antigen-positive cells may render NK cells relatively more resistant to the action of purinoceptor agonists such as ATP. Thus in females, immunosenescence results in a diminished ability of NK cells to transduce those signals that may normally mediate ATP-induced suppression of NK cytolytic activity. Such a diminished ability may be an immunobiological advantage to aging NK cells since they can be kept at a higher steady-state level of (anti-tumor cytotoxic) activity through a protection from negative modulators. These findings have an implication on the lower rate of mortality due to cancer seen in older women compared to that in older men. It is suggested that the ATP-NK cell interaction through the P2 purinoceptor may serve as a potentially useful model to study immunosenescence, ontogenic, or gender-specific changes in NK cells at the cell surface level.

Identification and functional characterization of a TIA-1-related nucleolysin

We recently reported the molecular cloning of a cytotoxic granule-associated RNA-binding protein designated TIA-1. The ability of recombinant TIA-1 to induce DNA fragmentation in permeabilized cells suggested that this protein is the granule component responsible for inducing apoptosis in cytolytic lymphocyte (CTL) targets. Here we report the characterization of a cDNA encoding a TIA-1-related protein designated TIAR. The deduced amino acid sequence of TIAR reveals it to be a 42-kDa protein possessing three RNA-binding domains and a carboxyl-terminal auxiliary domain. Although the RNA-binding domains of TIA-1 and TIAR share greater than 85% amino acid homology, their carboxyl-terminal auxiliary domains are only 51% homologous. The carboxyl terminus of TIAR contains a lysosome-targeting motif, indicating that TIAR is probably a cytotoxic granule-associated protein. Like TIA-1, purified recombinant TIAR induced DNA fragmentation in permeabilized target cells. Although immunoblotting analysis of post-nuclear supernatants revealed TIA-1 protein to be restricted to CTLs, PCR analysis revealed the expression of TIA-1 and TIAR mRNA transcripts in a wide variety of cell types. Our data suggest that the granules of CTLs contain at least two candidate nucleolysins involved in CTL killing.

Increased LAK activity against HIV-infected cell lines in HIV-1+ individuals

The role of natural killer (NK) cells and their inducible counterparts, lymphokine-activated killer (LAK) cells in AIDS with regard to HIV-1 viral immunosurveillance and the control of secondary opportunistic disease has yet to be established. In this study, we have demonstrated that LAK cells derived from all HIV-1+ groups showed striking increases in their capacity to lyse HIV-1-infected U-937 cells relative to their uninfected U-937 counterparts. Surprisingly, similarly derived LAK cells from healthy seronegative controls showed no differences in their lysis of HIV-1-infected versus uninfected U-937 cells. The differential ability of LAK effectors from seropositive donors to lyse HIV-1-infected targets was demonstrable using a number of U-937 subclones and their HIV-1-infected counterparts. Again, no differences in LAK cell-mediated lysis of HIV-1-infected and uninfected U-937 subclones were observed in seronegative individuals. Our findings that HIV-1+ individuals show selective expansion of non-MHC restricted, HIV-1-directed cytotoxic LAK cells indicate that natural immunity may indeed play a role in HIV-1 viral immunosurveillance.

Characterization and activation requirements of bovine lymphocytes acquiring cytotoxic activity after interleukin-2 treatment

Interleukin-2 (IL-2) treatment of cells and generation of non-major histocompatibility complex (MHC)-restricted cytotoxic cells from peripheral blood mononuclear leukocytes (PBML) was studied. Effector-target conjugate assays demonstrated that bovine PBML bound but did not lyse K562, HL60S and HL60R cells unless activated with IL-2. The magnitude of IL-2-activated killing of tumor cells as well as the magnitude of antibody-dependent cellular cytotoxicity depended on the IL-2 concentration. A short treatment (12-18 h) of effector cells with IL-2 was sufficient for development of cytotoxic activity. Withdrawal of IL-2 from the culture resulted in a reduction of cytotoxic activity that could be restored by further addition of IL-2. Cytotoxic activity of IL-2-activated populations obtained after nylon wool or Sephadex G-10 passage, and Percoll gradient centrifugation of PBML suggests that lymphokine-activated killer (LAK) cell activity in PBML is mainly mediated by a non-adherent lymphocyte lacking markers for B-cells. Positive and negative selection experiments using cell sorting confirmed these findings and demonstrated that the cell responsible for LAK cell activity in cattle belongs to a non-monocyte, non-B, CD2+ lymphocyte population. Furthermore, cytotoxic activity could not be generated in CD2+ populations enriched for cells expressing molecules equivalent to human and murine CD4 and CD8. These findings suggest that effector cells mediating non MHC-restricted cytotoxicity in cattle prevail in a population bearing a CD2+, CD4-, CD8- phenotype and that this population depends on the continuous presence of IL-2 for optimal cytotoxic function.

Reactivity of gamma delta T cells induced by the tumour cell line RPMI 8226: functional heterogeneity of clonal populations and role of GroEL heat shock proteins

The human tumour cell lines RPMI 8226 and Daudi are potent inducers of V gamma 9-expressing T cells. The inducing element of RPMI 8226 has not been defined but evidence suggests that a member of the GroEL heat shock protein (HSP) family (HSP 58) may have a role in the induction by Daudi cells. The present study examined the reactivity patterns of gamma delta T-cell clones generated in response to RPMI 8226 and addressed the possible role of HSP 58 in this process. RPMI 8226 induced a population of V gamma 9 TCR+ cells which were heterogeneous in terms of their cell surface markers, patterns of proliferation and cytotoxic responses. All clones expressed CD3, CD2, CD18 and CD29. They demonstrated variability in expression of CD56, CD8 and HLA-DR. RPMI 8226 stimulated proliferation in purified bulk gamma delta cultures and clones. Daudi was also capable of inducing these cells to proliferate while mycobacterial products were not effective. The clones demonstrated a limited non-MHC-restricted cytotoxicity pattern with some evidence of clonal heterogeneity. Although both Daudi and RPMI 8226 were sensitive to lysis by the clones, cold inhibition experiments indicated differential activity towards these targets. Anti-HSP 58 was inhibitory to gamma delta T-cell induction by RPMI 8226, Daudi and mycobacterial products. However, the anti-HSP 58 antibody appears to bind to the surface of at least six different tumour cell lines with no correlation to their ability to induce gamma delta T cells and the anti-HSP 58 inhibited non-gamma delta responses.

Rational immunotherapy with interleukin 2

Interleukin 2 (IL-2), a T lymphocyte product released upon antigen stimulation, has been used for cancer therapy in high doses for more than five years. More recently, its potential as a stimulant of cell-mediated immunity in infectious diseases, particularly those caused by intracellular microbes, has become appreciated. Drawing on the extensive information available as to the structure, cellular and molecular effects of IL-2, this review focuses on its use in patients with lepromatous leprosy and AIDS in low, physiologic doses. The data indicate that IL-2 is effective in stimulating cell-mediated immunity without systemic toxicity.

Analysis of CD16+dim and CD16+bright lymphocytes--comparison of peripheral and clonal non-MHC-restricted T cells and NK cells

The Fc gamma RIII receptor (CD16) has been described on natural killer cells and a small subset of T lymphocytes. CD16+bright lymphocytes represent the typical population of peripheral blood CD3- NK cells. In these studies in addition to CD16+bright NK cells Fc gamma RIII expressing cytotoxic T lymphocytes in peripheral blood from one healthy individual are characterized as CD16+dim non-MHC-restricted CTLs either expressing the alpha/beta (80%) or the gamma/delta T cell receptor (20%). Both CD16+ subsets are clearly distinct in their functional capacity performing NK and ADCC activity. Freshly isolated CD16+dim T cells exert higher ADCC, CD16+bright NK cells higher NK activity. They are also differentially activated by interleukin-2 since CD16+bright NK cells reveal a bright expression of the p75 IL-2 receptor beta-chain in contrast to the very low p75 expression on CD16+dim T cells. This activation leads to a gradual increase of ADCC by NK cells. Finally the CD16 expression pattern with low and bright intensity represents a stable phenotype expressed by clones generated from these different subpopulations. On a clonal level CD16+dim non-MHC-restricted T cells can be distinguished from CD16+bright NK cells by their lower capacity in NK killing, but they are equally potent in ADCC. Finally these CD3+CD16+dim clones provide the basis for studies of Fc gamma RIII and TcR interaction.

A study of lymphoma of large granular lymphocytes with modern modalities: report of two cases and review of the literature

Two cases of lymphoma of large granular lymphocytes are reported. The first case expressed natural killer (NK) cell, some T-cell (CD 2, CD 5, CD 8), and HLA-DR antigens, but was negative for other T-cell (CD 3, CD 4, CD 7), T-cell receptor (TCR), B-cell, and myeloid antigens. Germline configuration was demonstrated for TCR, and immunoglobulin heavy and light chain genes. The second case expressed NK cell, some T-cell (CD 3, CD 7, CD 8), and TCR antigens, but was negative for other T-cell (CD 4, CD 5), B-cell, myeloid, and HLA-DR antigens. Rearrangement of TCR alpha and beta chains were detected. Thus, the findings of case 1 were consistent with true NK cell lineage and case 2 with NK-like T-cell lineage. Our report underscores the heterogeneity of this newly recognized lymphoma, which nevertheless carries a consistently poor prognosis and is probably more prevalent in the Asian population. This study also provides information concerning immunophenotypes of cellular infiltrates in internal organs and cytogenetic abnormalities in this lymphoma; neither has been reported frequently in the literature. The importance of detecting cytoplasmic granules in tissue imprints or electron micrographs for differentiating other T-cell lymphomas is emphasized, and the classification of large granular lymphoproliferative disorders is discussed.

High endothelial venule and immunocompetent cells in typical medullary carcinoma of the breast

The characteristics of immunocompetent cells and their role in killing tumour cells in typical medullary carcinoma of the breast (TMC) have been investigated morphologically. Formation of high endothelial venule (HEV)-like vessels in tumour cell nests, the distribution of macrophages, T-zone histiocytes, T- and B-lymphocytes, the ratios of CD4+/CD8+, and natural killer (NK) or NK-like T-cells were examined in five cases of TMC. These results were compared with controls which consisted of three cases of ductal carcinoma with intense lymphocytic infiltration (control I) and four cases of ductal carcinoma with scanty lymphocytic infiltration (control II). An increased incidence of HEV-like vessels with migration of lymphocytes and a higher number of CD8+ lymphocytes with interleukin-2-receptor expression, as well as numerous CD57 cells, were noted in the tumour nests of TMC as compared with those of control groups. Furthermore, large granular lymphocytes, large lymphocytes invaginating tumour cells and necrotic tumour cells were observed electron microscopically. These findings indicate that infiltrating lymphocytes in TMC are activated and become effector cells that can kill the tumour cells by mechanisms similar to those of NK cells. The activities of immunocompetent cells in TMC appear to contribute to a favourable prognosis in TMC of the breast.

Interleukin-2 bolus therapy induces immediate and selective disappearance from peripheral blood of all lymphocyte subpopulations displaying natural killer activity: role of cell adhesion to endothelium

As early as 10-15 min after the start of a 30 min interleukin-2 (IL-2) infusion, a rapid, virtually complete disappearance of all natural killer (NK) lymphocyte subpopulations (including both CD3- CD56+ and CD3+ CD56+ cells with either alpha/beta or gamma/delta T-cell receptor) was observed from peripheral blood. In contrast, the number of T lymphocytes (CD3+ CD56-) was unmodified for at least 2 h after IL-2 injection. The IL-2-induced, rapid disappearance from peripheral blood of NK and NK-like lymphocytes may be related to their massive adherence to the activated endothelium. In this regard, IL-2 infusion caused a very rapid rise of tumour necrosis factor-alpha (TNF-alpha) plasma concentration, whereas other cytokines, such as interferon-gamma (IFN-gamma), were induced only at later times. In vitro experiments indicated that IL-2, either alone or better combined with TNF-alpha, exerts a rapid and selective stimulatory effect on NK adhesion to endothelial cells. On the basis of these findings, we suggest that the activation of NK lymphocytes induced by IL-2, alone or combined with TNF-alpha, plays a key role in mediating the massive and selective adherence of NK and NK-like cells following IL-2 bolus infusion.

Natural cytotoxic cell activity in the snake Psammophis sibilans

Thymocytes, splenocytes and peripheral blood mononuclear cells (PBMC) of the snake Psammophis sibilans consistently killed the human erythroleukemic cells K562 in a 4 h assay as judged by lactate dehydrogenase enzyme release. PBMC and splenocyte natural cytotoxicity (NC) increased proportionally with increase in the effector/target cell ratio. Spontaneous killer cell activity was consistently 2-3 times higher in peripheral blood (PB) than in spleen. On the other hand, thymocytes displayed low, yet detectable, NC. In an attempt to define the cell subpopulation responsible for natural killer (NK) activity, PBMC were depleted of macrophages or B lymphocytes before use in NK cell assays against K562 cells. Depletion of macrophages did not impair NK activity thus suggesting that macrophages do not mediate spontaneous lysis in the present 4 h assay. Conversely, removal of B lymphocytes by panning onto dishes coated with monoclonal antibody against snake Ig significantly reduced, but did not eliminate, PBMC spontaneous cytotoxicity. These data suggest that T, B and perhaps distinct NK cells participate in spontaneous lysis. This suggestion was confirmed by studies of NC in thymus, spleen and PB the year round. Strong NC was detected during spring and autumn when high numbers of leukocytes including T and B cells can be recovered from spleen and PB. Negligible spontaneous cytotoxicity was observed during early and mid-summer and in winter, periods of the year when snakes are thymus-less and contain few T and B cells in peripheral lymphoid organs. These findings, the first to document natural cytotoxic activity in snakes, were discussed in relation to the issue of NK cell identity in vertebrates.

Activation of human natural killer cells by the protein-bound polysaccharide PSK independently of interferon and interleukin 2

The protein-bound polysaccharide PSK was tested for the ability to activate human natural killer (NK) cells. When blood lymphocytes and purified CD3-CD16+ large granular lymphocytes (LGL) were treated in vitro overnight with PSK, they demonstrated enhanced NK cell activity against K562. The PSK-activated killer cells also lysed NK-resistant targets and freshly isolated autologous and allogeneic tumor cells. The PSK effect was observed with concentrations that could be obtained in the blood of cancer patients receiving oral administration of PSK. PSK-induced enhancement of NK activity was not abrogated by monoclonal antibodies (mAb) that neutralized interferon (IFN) alpha, IFN gamma, or interleukin-2 (IL-2). In addition, mAb reactive with p55 (alpha chain) or p75 (beta chain) glycoproteins of IL-2 receptors had no effects on PSK-enhanced NK activity even when used simultaneously. These results indicate that the PSK could activate human NK cells independently of IFN and IL-2/IL-2R systems.

Differential responses to interleukin 2 define functionally distinct subsets of human natural killer cells

Human natural killer (NK) cells can be subdivided into two populations based on the density of cell surface CD56 antigen. The great majority (approximately 90%) of NK cells express CD56 at low levels (the CD56dim phenotype), whereas a small NK cell subset (approximately 10%) exhibits approximately fivefold greater density of surface CD56. Exposure to exogenous interleukin 2 (IL 2) induces tenfold greater proliferation of CD56bright cells compared to CD56dim lymphocytes, even though both subsets constitutively express similar levels of intermediate affinity IL 2 receptor (IL 2R) p75 chains. Incubation with IL 2 alone or irradiated target cells alone could induce expression of the IL 2R p55 chain by both CD56bright and CD56dim NK cells; a combination of both stimuli was most effective. IL 2R p55 induction was evident after co-culture of NK cells with both NK-sensitive and NK-resistant cell lines or with antibody-coated target cells. Activation of NK cells with IL 2 plus target cells resulted in enhanced proliferation compared to activation with IL 2 alone; target cells alone did not induce significant proliferation. Although both NK cell subsets appeared to express high-affinity IL 2R p75/p55 heterodimers after stimulation with target cells and IL 2, proliferation of CD56dim cells remained minimal after such activation; activated CD56dim cells consistently demonstrated less proliferation to IL 2 than did resting CD56bright cells. In contrast, CD56bright NK cells exhibited even greater proliferation after stimulation with target cells. Almost all CD56dim NK cells expressed CD16 (Fc gamma R III) as well as the NK zeta chain, whereas less than 50% of CD56bright cells express either CD16 or zeta. CD56bright and CD56dim lymphocytes, thus, appear to represent distinct subpopulations of NK cells with different functional activities. Unlike CD56bright cells, CD56dim NK cells do not proliferate optimally to IL 2, even after the latter have been stimulated to express both IL 2R p55 and IL 2R p75. Efficient proliferation of CD56dim NK cells may, thus, require additional or alternative signals.

Immunomodulatory activity of a novel nucleoside, 7-thia-8-oxoguanosine: I. Activation of natural killer cells in mice

We reported recently that a novel immunomodulator, 7-thia-8-oxoguanosine (7T8OG)2 inhibited formation of pulmonary melanoma metastases (1), prevented against viral infection in mice (2) and potentiated the efficacy of a weakly immunogenic leukemia vaccine (3). Since certain tumor metastases and virus infected cells are targets to natural killer cells (NK cells), we now investigated whether 7T8OG is capable of activating NK cells in mice using NK cell sensitive YAC-1 and B16 and NK cell insensitive P815 targets. CBA/CaJ spleen cells incubated in vitro with 7T8OG at concentrations ranging from 0.005 to 0.5 mM responded with increased NK cell activity (32-62%) compared to controls (4-8%) to YAC-1 targets. Similar levels of augmentation in NK cell activity were observed when 40-168 mg/kg of 7T8OG was administered in vivo. In addition to the spleen, 7T8OG activated NK cells in the bone marrow (BM), the lungs, the liver, and in peritoneal exudate cells (PE). Although 7T8OG elicited activation of NK cells was observed as early as three hours after treatment, the maximal activity was observed after 24 h in the spleen; 12 h in the BM; 48 h in the lungs, and 72 h in PE. Administration of the drug by s.c., i.v., and i.p. routes all induced activation of NK cells in spleen, BM and PE. 7T8OG was found to activate NK cells in seven inbred and an outbred mouse strain, suggesting that the induced cytotoxicity against allogeneic and syngeneic tumor cells is not strain specific as well as independent of MHC restriction. C3H/He, CBA/CaJ and BDF/1 displayed higher levels of increased NK cell activity, whereas AKR mice were low responders. Low concentrations of IL-2 (0.25-5 U/ml) that induce little or no NK cell activity, when used in combination with 7T8OG, elicited significant enhancement of NK cell cytotoxicity. In contrast, IFN and 7T8OG showed no such synergism.

Immunological abnormalities in Kawasaki disease with coronary artery lesions

A review of our previous immunological studies on Kawasaki disease (KD) was undertaken. The results showed that peripheral blood macrophages/monocytes, T-cells and B-cells become activated during acute KD in terms of numerical changes in immunocompetent cells, expression of activated antigens on the cell surfaces and cytokine production. Also, during acute KD with coronary artery lesions (CALs) the numbers of macrophages/monocytes are increased. In addition, both the increased levels of tumor necrosis factor-alpha and shed intercellular adhesion molecule-1 in serum are more evident in KD patients with CALs than in those without. Our results further suggest that the main characteristics of the pathogenesis of KD are increased numbers of peripheral blood macrophages/monocytes with the secretion of monokines by these activated cells, and the expression of adhesion molecules on immunocompetent cells. These immune responses develop more vigorously in KD patients with CALs.

Cell-to-cell mediated inhibition of natural killer cell proliferation by monocytes and its regulation by histamine H2-receptors

Human peripheral blood monocytes, recovered by counter-current centrifugal elutriation, suppressed interleukin-2 (IL-2)-induced proliferation of autologous lymphocytes, recovered from low density Percoll fractions. Cell sorting experiments, analysis of phenotype of proliferating cells, and removal of defined cellular subsets by complement cytotoxicity revealed that IL-2-induced proliferation was confined to CD3-/16+/56+ natural killer (NK) cells. Monocyte-induced suppression of NK-cell proliferation was completed within 1 h of incubation with monocytes and unrelated to the formation of prostaglandins or other intermediary factors. The biogenic amine histamine, acting via H2-type histamine receptors (H2R) on monocytes, completely counteracted the monocyte-mediated suppression of IL-2-induced NK-cell proliferation. Our data are suggestive of a H2R-regulated, cell-cell-mediated mechanism by which monocytes down-modulate NK-cell proliferation.

Subset markers of CD8(+) cells and their relation to enhanced cytotoxic T-cell activity during human immunodeficiency virus infection

Using fresh whole blood or isolated lymphocytes, the activity of in vivo generated cytotoxic T-lymphocytes (CTL) was measured as the OKT3-specific lysis of HL-60 targets, in a cross-sectional study of 53 HIV (+) patients. CTL activity in the entire HIV(+) group was two to three times higher than in HIV(-) controls, with WHO stage 3 (=pre-AIDS) patients showing the highest cytolytic function. The whole-blood CTL assay was validated and its practical and theoretical advantages are discussed. Within the CD8(+) cells, the number and proportion of the CD45RO(+) "memory" subset were significantly increased in HIV(+) subjects. The HLA-DR(+) subset rose most spectacularly in the asymptomatic stage of the infection, while the CD38(+) subset was the only one still significantly rising between the pre-AIDS and the AIDS stage. CTL activity was most closely correlated with T8 cells expressing the CD38 marker. In the context of CTL, CD38 thus seems to reflect activation rather than immaturity. Lymphocytes from HIV(+) subjects with a high OKT3-specific lytic capacity also destroyed normal lymphoblasts to a significant extent, pointing to their possible involvement in an autodestructive process. Our data thus suggest the importance of T8 cytolytic function and/or T8 subtyping in the immunopathogenesis and the prognosis of HIV infection.

Monocyte-induced down-modulation of CD16 and CD56 antigens on human natural killer cells and its regulation by histamine H2-receptors

Human natural killer (NK) cells carry CD16/FcR and CD56 cell-surface Ag but lack the T-cell marker CD3. Here we show that incubation of resting human NK cells with CD3-/16+/56+ phenotype with autologous monocytes induced the disappearance of CD16 and CD56 cell-surface Ag on NK-cells but did not affect CD2 or CD3 Ag expression on T-cells. Monocyte-induced down-modulation of NK-cell-surface Ag was cell-contact dependent and induced only by freshly isolated monocytes, recovered from peripheral blood by counter-current centrifugal elutriation. Adherence of monocytes abrogated the capacity to induce down-modulation of NK-cell-surface Ag. The biogenic amine histamine dose-dependently reversed the monocyte-induced down-modulation of CD16 and CD56 on CD3- NK-cells. The effect of histamine was mediated by H2-type receptors on monocytes. The data presented are suggestive of a cell-cell-mediated interaction between monocytes and NK-cells which modulates surface expression of NK-cell Ag and its histaminergic regulation.

Cytotoxicity of human natural killer (NK) cell subsets for Plasmodium falciparum erythrocytic schizonts: stimulation by cytokines and inhibition by neomycin

Quantification of human peripheral blood NK subsets has been made in a group of Kenyan adults and children with acute P. falciparum malaria. Results were compared with data obtained from three age- and sex-matched control cohorts: parasitaemic but asymptomatic children; aparasitaemic children and adults; and adult Caucasians with no previous history of malaria. Separated NK subsets were tested in vitro for cytotoxicity to erythrocytic schizonts of P. falciparum in the presence and absence of cytokines. There was a statistically significant quantitative and qualitative depression of the CD3-CD56+ subset in patients with acute malaria and this was accompanied by an expansion of the 'non-functional' CD3-CD57+CD16-CD56- subset. Both CD3-CD16+ and CD3-CD56+ NK cells from all patients and donors lysed schizonts, and this cytotoxicity was enhanced by the addition of recombinant interferon-alpha and/or IL-2, notably with the CD3-CD56+ subset. Interestingly, asymptomatic donors had the highest levels of CD3-CD56+ NK cells, which also demonstrated an enhanced response to cytokine stimulation. Cytotoxicity to schizonts was accompanied by the release of soluble NK cell lytic factors. Neomycin suppressed cytotoxicity in a dose-dependent manner, indicating that the lysis of schizonts by NK cells involves phospholipase C-mediated phosphoinositide metabolism. Our findings define a role for NK cells in immunity to malaria through the lysis of infected erythrocytes as a first-line defence against the parasite.

Lysis of fresh human tumor cells by autologous peripheral blood lymphocytes and tumor-infiltrating lymphocytes activated by PSK

The protein-bound polysaccharide PSK was tested for the ability to induce in vitro autologous tumor killing (ATK) activity in human cancer patients. Peripheral blood lymphocytes (PBL) and tumor-infiltrating lymphocytes (TIL) demonstrated various levels of cytotoxicity against autologous, freshly isolated tumor cells. When PBL and TIL were cultured overnight with PSK, ATK activity was induced in previously non-reactive cases and augmented in previously reactive samples. The PSK effect was observed with PSK concentrations of 10-100 micrograms/ml that could be obtained in the blood of cancer patients who received standard oral administration of PSK. The manifestation of PSK-induced ATK required active cell metabolism and RNA and protein syntheses, but not DNA synthesis of lymphocytes. PSK-induced enhancement of ATK was not abrogated by monoclonal antibodies (mAb) directed against interferon (IFN) alpha or IFN gamma. In addition, mAb that neutralized interleukin-2 (IL-2) or mAb reactive with alpha-chain or beta-chain of IL-2 receptors (IL-2R) had no effect on PSK-induced ATK activity. Supernatants from PSK-stimulated lymphocyte cultures did not induce ATK. Cell fractionation experiments revealed that CD3-CD16+ large granular lymphocytes (LGL) and/or CD3+CD16- T lymphocytes were responsible for both spontaneous and PSK-induced ATK. PSK-activated LGL, but not T lymphocytes expressed lysis of fresh allogeneic tumor cells. These results indicate that PSK activates PBL and TIL to exhibit ATK independently of IL-2/IL-2R systems.

Immunomodulation by 9-amino-1,2,3,4-tetrahydroacridine (THA): 1. Down-regulation of natural cell-mediated cytotoxicity in vitro

THA (Tacrine), a drug used in the experimental therapy of dementia of Alzheimer's disease type, and whose biochemical site of action is believed to be the neural cholinesterase, is shown, for the first time, to be an immunosuppressant in vitro on normal human peripheral blood lymphocytes in microgram quantities. THA down-regulates non-MHC restricted natural killer (NK) cell activity without affecting the general viability of cells. This down-regulation can be demonstrated at all effector and target (K562) concentrations, in purified resting NK cells as well as in lymphokine (interleukin 2) activated killer cells in 3- or 16-h NK assays and in all the blood samples tested. Kinetic analysis shows that the Vmax (maximal cytotoxic potential) and Km of NK cell-mediated cytolysis are also attenuated. Single cell assays using agarose matrix reveal that THA moderately interferes with tumor target binding/recognition events and strongly abrogates the delivery of lethal hit, thus lowering the frequency of active killer cells among THA-treated lymphocytes. THA down-regulates NK cells upon direct interaction and does not require the help of non-NK cells. The THA sensitive site(s) on NK cells does not appear to be perturbed significantly either by their proliferative status or by membrane modulations that may be normally induced by interleukin 2. The in vitro immunomodulatory pharmacological properties of THA reveal that the biological site of action of THA extends to non-neural cells also. Such non-neural models may be helpful in exploring the pathophysiological neuroimmunomodulatory properties of THA at cellular and molecular levels.

Women with endometriosis show a defect in natural killer activity resulting in a decreased cytotoxicity to autologous endometrium

OBJECTIVE

The role of natural killer (NK) cells in the decreased cellular immunity of women with endometriosis was investigated.

DESIGN, SETTING, PATIENTS

Thirty-four women were investigated prospectively before a CO2-laser laparoscopy for infertility and/or pain at the University Hospital Gasthuisberg. Endometriosis was scored blindly.

MAIN OUTCOME MEASURE

The cytotoxicity, directed against the endometrium, was mediated by NK cells because this cytotoxicity could be removed by treating the effector cells with the NK-specific anti-Leu-11b monoclonal antibody. Consequently, we evaluated prospectively in those women the lymphocyte-mediated cytotoxicity toward NK sensitive (K562-assay) and autologous endometrial target cells.

RESULTS

The NK activity (K562-assay) and the cytotoxicity against autologous endometrial cells were similarly decreased in women with endometriosis and correlated with the severity of the disease. Using heterologous effector cells, the decreased chromium release in women with endometriosis was less pronounced but still present.

CONCLUSION

The decreased cytotoxicity to endometrial cells in women with endometriosis is mainly because of a defect in NK activity but is also partially because of a resistance of the endometrium to NK cytotoxicity.

Lymphokine-activated killer (LAK) cells. VI. NK1.1+, CD3+ LAK effectors are derived from CD4-, CD8-, NK1.1- precursors

Normal murine splenocytes cultured with IL2 for 6, but not 3, days contained an NK1.1+, CD3+ lytically active subset. These lymphocytes were not derived from NK1.1+ precursors since NK1.1+ cells, purified by flow cytometry, failed to express CD3, as determined by the 145-2C11 mAb, on their surface even after culture with IL2 for 6 days. Instead, the precursors of the NK1.1+, CD3+ effectors were contained in a B cell-depleted CD4-, CD8-, NK1.1- splenic subset. Freshly obtained CD4-, CD8-, NK1.1- splenocytes were mostly CD3+, CD5+, B220-, had no spontaneous lytic activity against YAC-1, and were unable to mediate anti-CD3 directed lysis against FcR-bearing target cells. Culture of the CD4-, CD8-, NK1.1- splenocytes with IL2, for 6 days, resulted in the development of NK1.1+, CD3+, B220+ effectors 40% of which were CD5dim and 20-25% of which expressed TCR-V beta 8 as determined by the F23.1 mAb. The acquisition of NK1.1, B220, and lytic activity by this triple-negative subset was readily inhibited by cyclosporine A (CSA). On the other hand, CSA had no effect on the acquisition of B220 or lytic activity by NK1.1+ precursors obtained by flow cytometry sorting. Moreover, all of the NK1.1+ cells generated by IL2 culture of splenocytes obtained from mice depleted of NK1.1+ lymphocytes (by in vivo injection of anti-NK1.1 mAb) coexpressed CD3 on their surface and were thus distinct from classical NK cells. These findings demonstrate that splenic NK cells do not express or acquire CD3; that the NK1.1+, CD3+ LAK effectors are derived from an NK1.1- precursor; and that CSA is exquisitely selective in its inhibitory effect on LAK generation.

Activation of CD16+ effector cells by rheumatoid factor complex. Role of natural killer cells in rheumatoid arthritis

The role of natural killer (NK) cells in rheumatoid arthritis (RA) remains unclear. A pathogenetic function of rheumatoid factors (RF) also has not been defined. In the present studies, natural killer (NK) cells were examined as a model for FC gamma receptor type III-positive (FC gamma RIII+) cells, with regard to their interaction with RF. NK cell antigen CD16 (FC gamma RIII) and CD56 expression and functional NK and antibody-dependent cell-mediated cytotoxicity (ADCC) activity were compared in peripheral blood lymphocytes and autologous synovial fluid lymphocytes (SFL) of RA patients. Peripheral blood lymphocytes and SFL showed normal CD56 expression. In contrast, both the frequency and the density of CD16 antigen were decreased in SFL. Furthermore, diminished NK cytotoxicity and a significant decrease in ADCC were observed in SF NK cells. In subsequent in vitro studies with normal fresh NK cells, it was demonstrated that IgG-containing RF complexes from RA patients induced a modulation of FC gamma RIII structure from the NK cell surface, a decrease in NK activity, and a complete loss of ADCC. When purified RF was incubated with NK-enriched cell lines from RA patients, increased transcription and subsequent production of interferon-gamma and tumor necrosis factor alpha were observed. These data suggest a direct involvement of RF complexes in the pathogenetic process of chronic inflammation in RA.

Cytotoxic activity and phenotypic characteristics of lymphocyte subsets after therapy of cancer patients with interleukin-2

After a 5-day period of continuous intravenous infusion of recombinant interleukin 2 (rIL-2) in seven patients with malignant melanoma or gastric or pancreatic cancer, different lymphocyte subsets were separated from patients' blood and tested ex vivo for cytotoxic activity against various tumour cell lines. Lytic activity was mediated by CD3+CD56+, CD3-CD56+, CD3-CD2+ and CD8+CD56+ lymphocytes. No cytotoxic activity could be observed within the CD3+CD56-, CD3+CD2+ or CD4+ T cell subsets. To characterize CD56+ cytotoxic cells further, the expression of other antigens on this population was analysed before and after IL-2 therapy. CD3, CD4, CD16 and CD57 antigens were weakly expressed, and the IL-2 receptor (CD25) was not detectable on these cells either before and after treatment with IL-2. In contrast, increased expression of CD2. CD8 and HLA-DR antigens occurred following therapy. The divergence of CD3 and CD8 antigen expression after IL-2 therapy was caused by an increase in CD3-CD8+ cells, detectable as a low-density CD8+ subset. This study shows that cytotoxic activity of in vivo IL-2-activated killer cells is predominantly, but not exclusively, mediated by CD3-CD56+ lymphocytes, partially coexpressing the CD8 antigen and lacking the expression of CD16 antigens.

Interleukin-2-activated murine cell lines with macrophage- and B-lymphoblast-lytic activity

Interleukin-2 (IL-2)-activated murine killer cell lines with macrophage- and B-lymphoblastic-lytic activity were established, and their target specificity, surface markers, recognition-related structures, and requirements for optimal cell growth were characterized. Sustained growth of IL-2-activated lymphocytes was supported by the combination of IL-2 and IL-4-enriched T cell conditioned medium (CM), but was not supported by IL-2 alone or the combination of IL-2 and IL-3-containing CM in the presence of macrophages (M phi). The established line required continuous contact with M phi to maintain anti-M phi cytolytic activity. Flow cytometric analysis showed that the original line isolated by the first cloning was Thyl+, CD4-, and weakly CD8+, FcR+. The majority of these cells were CD3+ and TCR-V beta 8+. From this line, the CD3+, TCR-V beta 8+ and CD3-, TCR-V beta 8- clones were isolated by subcloning. The former clone showed Thyl+, CD3+, CD4-, CD8-, TCR-V beta 8+, FcR(+)-phenotype, and the latter clone showed Thyl+, CD3-, CD4-, CD8-, TCR-V beta 8-, FcR- phenotype. The original line and subclones showed a similar target specificity and killed resident or thioglycollate (TG)-induced peritoneal M phi and B-lymphoblasts, but did not kill T-lymphoblasts. Allogeneic M phi, M phi-like cell line P388D1, and B cell hybridoma were sensitive, whereas fresh lymphocytes, T cell lymphoma BW5147, natural killer (NK)-sensitive YAC-1, and NK-resistant P815 tumor cells were resistant to lysis by these cytotoxic lines. The addition of anti-H-2 heteroserum, anti-MHC class 1, anti-MHC class II, anti-CD3, or anti-TCR-V beta 8 monoclonal antibody (mAb) to assay cultures did not inhibit the anti-M phi cytolysis by these killer cells. In addition, the CD3- TCR-V beta 8- clone killed M phi and B lymphoblasts better than the CD3+, TCR-V beta 8+ clone. These results suggest that cytotoxic lines established in this study do not use the T cell receptor (TCR) molecules to recognize target cells and the MHC molecules are not involved in recognition. Anti-LFA-1 mAb partially inhibited anti-M phi-lysis, suggesting that the cell contact between targets and effectors is important in cytolysis. Our present data suggest that the culture condition containing IL-2, IL-4, and M phi may support the continuous growth of non-MHC-restricted killer cells with relative target specificity against M phi and B-lymphoblasts.