Demonstration of clonality, by X-linked DNA analysis, in chronic natural killer cell lymphocytosis and successful therapy with oral cyclophosphamide

The expanded lymphocyte population in large granular lymphocyte (LGL)-leukemia carries the phenotypic characteristics of either cytotoxic T lymphocytes (CD3+,CD8+) or natural killer (NK) cells (CD3-,CD15+). In the former subset, clonality has been demonstrated by T-cell receptor gene rearrangement studies. Since NK cells do not rearrange T-cell receptor genes, the neoplastic nature of chronic NK cell lymphocytosis has not been well defined. We used X-linked DNA analysis to study the clonal nature of an expanded NK cell population in a patient with a 3-year history of relative lymphocytosis associated with anemia and neutropenia. Southern blot analysis showed no clonal T-cell receptor gene rearrangement. The majority of the circulating lymphocytes had a NK cell phenotype and demonstrated both direct NK cell-mediated cytotoxicity and antibody-dependent cellular cytotoxicity. However, the in vitro growth characteristics of these cells did not suggest that they were polyclonal expansions of normal NK cells. To determine directly the clonal origin of these cells, we performed X-linked DNA analysis. Density gradient centrifugation methods were used to isolate mononuclear cells, and NK cells were positively selected by CD16-immunoconjugated magnetic beads. The DNA of these cells was analyzed by restriction fragment length polymorphism-methylation strategy and showed a monoclonal pattern of X-chromosome inactivation while a polyclonal pattern was obtained in corresponding skin tissue. Treatment of the patient with oral cyclophosphamide resulted in complete hematologic remission. We conclude that chronic NK lymphocytosis may be clonal and responsive to immunosuppressive therapy.

Epstein-Barr viral DNA in acute large granular lymphocyte (natural killer) leukemic cells

Serologic studies in a male Caucasian presenting with an acute hepatitis-like illness, associated with an increase in peripheral blood large granular lymphocytes (LGLs), suggested a chronic or reactived Epstein-Barr virus (EBV) infection. The LGL were shown to have a natural killer (NK) cell, CD3- CD16- CD56+ CD57- phenotype and mediated strong nonspecific major histocompatability complex-unrestricted (NK) cytotoxic activity. A progressive increase in the peripheral blood LGL count was associated with a rapid deterioration, hepatic necrosis, and death. Widespread organ infiltration with LGLs suggested a malignant lymphoproliferative condition, but no lymphoid (T-cell receptor or IgH) gene rearrangement or cytogenetic marker was detected. However, molecular analysis identified EBV genomic DNA present in a single episomal form within the LGL, establishing the clonal nature of the LGL proliferation. Confirmation that the EBV had infected the leukemic LGL was obtained by in situ hybridization studies that showed EBV RNA within the LGLs. Immunoblotting of LGL protein extracts established that, of the EBV gene products, EBV nuclear antigen-1 (EBNA-1) was expressed but EBNA-2 and the latent membrane protein (LMP-1) were not detectable in the leukemic cells. These results suggest that EBV may be involved directly in LGL cell transformation, in a manner similar to EBV-associated B-cell lymphomas, although other molecular changes probably contribute to the evolution of a fully malignant leukemic clone.

Natural killer cell surface markers on cells containing parallel tubular structures

Parallel tubular structures (PTS) and/or the associated electron-dense granules, thought to contain molecules responsible for target cell lysis, can be detected in the cytoplasm of lymphocytes with large granular lymphocyte (LGL) morphology. In the present study we compared PTS presence in freshly isolated peripheral blood lymphocytes and peripheral blood lymphocytes incubated overnight in the presence of human pooled serum, sera from patients with Hodgkin's disease and interferon-alpha. Under all conditions we found PTS in the majority of CD16+ cells (64.3-74.8%) but less than 41.8% in CD57+ cells. In the case of double-labeled lymphocytes, 41.0-61.7% CD16+/8+ but only 24.2-27.5% CD57+/8+ cells were PTS+. Thus, in all cases where lymphocytes expressed CD16 antigen there was a high percentage of PTS positivity. Although the PTS+ cells exhibited phenotypic heterogeneity there was, except for a proportion of CD57+ lymphocytes which exhibited less of the characteristic LGL features, generally LGL morphological homogeneity. CD16 lymphocytes are potentially more cytotoxic than CD57 and CD8 cells. Taking this into consideration, the presence of the PTS in the majority of CD16 cells suggests an important role for PTS in target cell lysis.

Effects of hyperthermia on natural killer cells: inhibition of lytic function and microtubule organization

Cells with natural killer activity (NK) may play an important role in host defence against tumour cells. The lytic function of NK cells is very sensitive to hyperthermic inactivation. However, cells with NK activity isolated from rat spleen and exposed to 41-42.5 degrees C for 30 min could partially recover their cytotoxic activity after incubation at 37 degrees C. The recovered cytotoxicity was still NK-specific, as it only resulted in the lysis of YAC-1 sensitive targets, and could not lyse NK-resistant P815 mastocytoma cells. Conjugate formation assay using NK cells labelled with specific monoclonal antibody (mAb) 3.2.3 indicated that the binding of NK cells to targets was not significantly affected by heat treatment. Compared to controls, however, microtubule organizing centre (MTOC) reorientation towards the region of intercellular contact was reduced by 40% in heated effector cells. This was accompanied by a greater inhibition (62-77%) of NK lytic activity. Kinetic analysis indicated that MTOC reorientation capacity recovered following incubation at 37 degrees C. MTOC recovery was maximal 4 h after treatment whereas that of lytic activity peaked at 6 h. These data indicate that NK cells recover NK-specific lytic activity after heat inactivation. Moreover, our study demonstrates that hyperthermia interferes with post-binding MTOC reorientation, and further supports a role for microtubule in secretory processes involved in NK-mediated cytolysis.

Electron microscopic observation of killer cells induced by mixed culture of lymphocytes with autologous cancer cells and further culture with recombinant interleukin-2

Peripheral blood lymphocytes obtained from 2 patients with hypopharyngeal cancer were cultured with mitomycin C treated autologous tumor cells (autologous MLTC) for 10 days and further cultured with recombinant interleukin 2 (rIL-2). In one case 10-day MLTC induced increase of CD25-positive lymphocyte count, indicating that IL-2 receptors were expressed dominantly by the autologous tumor stimulation, and further culture with rIL-2 differentiated killing activity against autologous tumor cells. In the other case, however, MLTC alone induced killing activity against autologous tumor cells, indicating that the tumor cells from this patient might possess stimulatory activity sufficient to induce mature killer cells. Electron microscopic observation of the morphological features of lymphocytes cultured for 10 days revealed mostly small lymphocytes with low incidence of cytoplasmic granules. Further culture with rIL-2, however, induced slightly larger lymphocytes with well-developed microvilli, and cytoplasmic granules were found in many of the cells. Lymphokine activated killer (LAK) cells induced by culture of lymphocytes with rIL-2 alone were much larger and had long microvilli and abundant cytoplasmic granules, and were apparently morphologically different from the killer cells initiated by MLTC. The small lymphocytes induced by autologous MLTC alone might be autologous tumor specific cytotoxic T lymphocytes (CTL) and/or CTL precursors. Further culture with rIL-2 induced maturation of the CTL. However, the nature of the cytoplasmic granules remains obscure.

CD3 negative "small agranular lymphocytes" are natural killer cells

We describe here that CD3-, CD16+ and/or CD56+ small lymphocytes, in a highly reproducible fashion, mediate a significant level of K562 killing that is, on a "per cell" basis, comparable to the cytolytic activity of CD3- LGL. The CD3- small lymphocytes appeared to have no granules based on light and electron microscopy and lack of right-angle scatter on the FACS; we thus refer to them as small "agranular" lymphocytes (SAL). The lytic activity against K562 is inhibited by treatment with either L-leucine methyl ester or EGTA, which are reported to effect granule-dependent killing. We suggest that the SAL have lytic molecules in their cytoplasm (which are sensitive to these treatments) but that these molecules are not organized into discrete granules as found in LGL. The CD3- SAL are phenotypically very similar to LGL and both SAL and LGL mediated equal and reproducible antibody-dependent cell-mediated cytotoxicity. These observations force redefinition of the concept of NK cells to include both CD3- LGL and CD3- SAL.

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

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

Responses of murine natural killer cells to binding of the fungal target Cryptococcus neoformans

Natural killer (NK) cells bind to and inhibit the growth of the fungal target Cryptococcus neoformans. Since C. neoformans is structurally and chemically distinct from the standard tumor cell target used in the model of NK cell-mediated cytotoxicity, this study was designed to investigate the NK cell response after binding to cryptococci. Transmission electron micrographs and three-dimensional reconstructions of NK cell-cryptococci conjugates demonstrated focusing of the NK cell centrioles and Golgi apparatus toward the cryptococcal attachment site. NK cell cytoskeletal changes after cryptococcal binding were confirmed by immunofluorescence studies in which NK cells were allowed to bind to cryptococci in Mg2(+)-containing, Ca2(+)-free medium. One hour after the addition of Ca2+ to the preformed conjugates, the bound NK cells demonstrated a significant increase in the percentage of microtubule organizing centers focused toward the cryptococcal binding site. Colchicine, a drug that inhibits microtubule assembly, did not affect NK cell-cryptococci binding but abrogated NK cell-mediated cryptococcal growth inhibition, indicating that microtubule assembly, an important prerequisite for the secretory process, is not required for NK cell-cryptococci binding but is essential for inhibition of cryptococcal growth. In addition, the Ca2+ channel-blocking reagents, lidocaine and verapamil, did not affect NK cell-cryptococci binding but blocked the NK cell-mediated anticryptococcal activity, suggesting that a Ca2+ flux is essential for inhibition of cryptococcal growth. Considered together, these data indicate that NK cells respond to binding of a target cell that has a capsule and cell wall, in addition to a cell membrane, in a manner similar to that seen following binding to target cells that are surrounded by only a cell membrane; however, the response of the NK cells to the binding of C. neoformans is slower and possibly less efficient than the response after tumor cell binding.

Functional p75 interleukin-2 receptor expression on the fresh blast cells in childhood acute lymphoblastic leukemia with natural killer cell properties

Neoplastic cells of childhood acute lymphoblastic leukemia (ALL) with natural killer (NK) cell properties were studied for the expression of p75 interleukin-2 receptors (IL-2R) and the receptor functions. Freshly prepared blast cells from a patient with ALL had NK cell properties: (1) the phenotype such as CD56+, CD2+, E-rosette+, CD3-, and CD19-; and (2) the presence of spontaneous cytotoxicity against NK-sensitive K562 target cells. Although p55 Tac antigen was not detectable, there was the expression of p75 IL-2R on the freshly prepared blast cells: 70% of the cells reacted with Mik-beta 1 monoclonal antibody against p75 IL-2R as determined by flow cytometry. Two-color flow cytometry revealed that the blast cells expressed both p75 IL-2R and NKH-1. NK activity of the blast cells was augmented by their treatment with 1,000 U/ml recombinant IL-2 (rIL-2): the cytotoxicity level as percentage lysis increased to 38.7% from 22.0% when the normal lymphocyte value increased to 62.1% from 46.2%. Although the blast cells possessed no apparent level of proliferative capacity, the addition of 1,000 U/ml rIL-2 yielded a 2.7-fold increase in their thymidine uptake. These results demonstrate the expression of functional p75 IL-2R on the patient's blast cells with NK cell properties.

The intracellular distribution of cell organelles in natural killer cells during the cytolysis of bound tumor cells, with special reference to the rod-cored vesicles

The secretory function of the natural killer (NK) cells has been considered to be essential for cytolytic activity against their target cells. In this study, the distribution and spatial relationship of various cell organelles which participate in the secretory process, i.e., Golgi apparatus, vesicles, granules and microtubules, were examined ultrastructurally in non-treated and OK-432-activated rat NK cells bound to the tumor cells, with special reference to the rod-cored vesicles which are the most characteristic structure of the NK cells. Rod-cored vesicles and their closely related structures, "empty" vesicles, were derived from the end portion of the Golgi trans cisternae and became accumulated in the central area which was surrounded by the Golgi apparatus, nucleus and contact surface. Some of the vesicles appeared to be further transported to the contact area along the microtubules extending from the centrioles toward the bound targets. The access of the vesicles to the contact surface occurred at that portion where subplasmalemmal actin lattice was thin. The distribution of the dense granules and multivesicular bodies was similar to that of the vesicles, but the area of their occurrence was a little wider. At the outer aspect of the Golgi apparatus was situated the endoplasmic reticulum from which transitional vesicles came to the inner or cis cisternae of the apparatus. The present observations indicate that the cell organelles of the conjugated NK cells are purposefully arranged in the cytoplasm in such order that the generated rod-cored vesicles and "empty" ones are efficiently directed toward the bound tumor cells.

Immune resistance of man in space flights

The immune system of 72 cosmonauts was studied after their flights on board Salyut 6, 7 and Mir orbital stations. PHA lymphocyte reactivity, T helper activity and NK capacity to recognize and kill the target were decreased on 1-7 days after prolonged (3-11 months) space flights. Certain alterations were found in the ultrastructure of the NK secretory and locomotor apparatuses. Decrement of IL 2 production was shown using the biological test. However immunoenzymatic analysis did not reveal a decrease in IL 2 synthesis. Production of a alpha-interferon remained unchanged while that of gamma-interferon either rose or was diminished. Several cosmonauts displayed a trend towards increased OAF production. The observed decrease in immune system functioning may increase the risk of various diseases during prolonged space flights.

Application of laser optical tweezers in immunology and molecular genetics

Optical tweezers, based on a compact diode pumped Nd:YAG laser providing 350 mW at 1,064 nm coupled into a Zeiss IM 35 microscope, were used to sort CD4+ T cells into a capillary for further mechanical handling and to establish contact between single human natural killer (NK) cells and human erythroleukemia cells (K562) as targets. After contact and a lag phase of a few tens of seconds, the target cell starts to change its morphology and membrane blebbing occurs. The kinetics of the attack of the NK cell on K562 cells is not straightforward but governed by temporal oscillations in the shape of the target cell (zeosis). In a second application, the optical tweezers are combined with a UV laser microbeam based on a pulsed UV laser and with flow cytometry and sorting. With the pulsed laser, segments of sorted chromosome 1 of the chinese hamster karyotype (CHV 79) can be easily micro-dissected and subsequently collected using the optical tweezers. This allows preparation of a few hundred chromosome segments per day without mechanical contact and in an absolutely sterile way and thus may provide an interesting basic technique in any type of genome sequencing project.

Natural killer (NK) activity of cultured S100 beta-positive T-leukemia cells

In order to clarify the function of human S100 beta-positive T-cells, S100 beta-positive T-leukemia cells (S100 beta TLC) were examined in vitro. S100 beta TLC were obtained from the peripheral blood of a patient with S100 beta-positive T-cell leukemia and enriched by an E-rosetting method. Two dimensional flow cytometric analysis indicated that the vast majority of the E-positive fraction were S100 beta TLC expressing CD3 and CD8 antigens. Although S100 beta TLC expressed CD3 antigen, they were negative for the alpha/beta and gamma/delta T-cell antigen receptor (TCR) defined by monoclonal antibodies (mabs) WT-31 and delta TCS-1, respectively. It was speculated that S100 beta TLC initially expressed alpha/beta TCR but lost it during malignant transformation. When S100 beta TLC were cultured for 24 h, they acquired cytotoxic activity towards various NK-sensitive cell lines including K-562, Molt-3 and CEM-CCLF, but did not exhibit lysing activity towards NK-resistant cell lines including Raji, Daudi and MT-1. Despite the NK-activity of cultured S100 beta TLC, they lacked the morphological features of large granular lymphocytes (LGL). S100 beta TLC did not exhibit lymphokine-activated killer (LAK) activity. When S100 beta TLC were cocultivated with NK-sensitive cells or NK-resistant cells, they selectively bound to NK-sensitive cells, indicating that they lysed target cells by cell-to-cell contact. The finding that S100 beta TLC lacked TCR molecules and their NK activity was not inhibited by mabs reactive with the CD3-TCR complex indicated that the CD3-TCR complex was not involved in their target recognition.(ABSTRACT TRUNCATED AT 250 WORDS)

The lytic granules of natural killer cells are dual-function organelles combining secretory and pre-lysosomal compartments

Cytolytic lymphocytes contain specialized lytic granules whose secretion during cell-mediated cytolysis results in target cell death. Using serial section EM of RNK-16, a natural killer cell line, we show that there are structurally distinct types of granules. Each type is composed of varying proportions of a dense core domain and a multivesicular cortical domain. The dense core domains contain secretory proteins thought to play a role in cytolysis, including cytolysin and chondroitin sulfate proteoglycan. In contrast, the multivesicular domains contain lysosomal proteins, including acid phosphatase, alpha-glucosidase, cathepsin D, and LGP-120. In addition to their protein content, the lytic granules have other properties in common with lysosomes. The multivesicular regions of the granules have an acidic pH, comparable to that of endosomes and lysosomes. The granules take up exogenous cationized ferritin with lysosome-like kinetics, and this uptake is blocked by weak bases and low temperature. The multivesicular domains of the granules are rich in the 270-kD mannose-6-phosphate receptor, a marker which is absent from mature lysosomes but present in earlier endocytic compartments. Thus, the natural killer granules represent an unusual dual-function organelle, where a regulated secretory compartment, the dense core, is contained within a pre-lysosomal compartment, the multivesicular domain.

Cytolytic human lung lymphocytes: characterization of intragranular protease content and response to interleukin-2

Cytolytic lymphocytes play an important role in defense against viral and neoplastic disease. Integral to the function of these cells is the content of lysosomal granules. Recent attention has focused on a family of proteases present in the granules of natural killer (NK) cells, interleukin-2 (IL-2)-activated NK cells (LAK cells), and cytotoxic T lymphocytes (CTL). In the current investigation, lymphocytes were obtained from human lung parenchyma and peripheral blood. Following activation with IL-2, both groups of lymphocytes exhibited comparable cytolytic activity against K562 targets. Lysosomal granules obtained from these cells contained two serine proteases with molecular weights of 30 and 28 kD. These proteases were capable of hydrolyzing benzyloxycarbonyl-L-lysine thiobenzyl ester (BLT-ester), a substrate of cytolytic lymphocyte proteases. When compared to blood, unactivated lung lymphocytes contained significantly higher levels of protease content. Although IL-2 produced a significant increase in blood lymphocyte protease content, no change in lung lymphocyte granule protease activity was observed. We conclude that cytolytic lung lymphocytes contain high levels of lysosomal granule protease but differ from blood lymphocytes in the ability to increase protease content following activation with IL-2. The high level of protease content in cytolytic lung lymphocytes suggests that these cells could produce local tissue injury during the release of lysosomal granules.

Purification and characterization of cytolytic and noncytolytic human natural killer cell subsets

Natural killer (NK) cells form three functionally distinct populations of effectors: competent cytolytic effectors able to bind and kill target cells and two subsets of nonlytic effectors, one able and the other unable to bind target cells. A flow cytometric method was developed, based on size and two-color fluorescence of NK cell-target conjugates, for the characterization and sorting of highly purified subpopulations--killer cells, nonkiller binder cells, and free cells. Ultrastructural examination revealed that granule content was reduced in the killer cells and absent in most of the binder cells. Quantitative differences in the expression level of HLA class I, CD11b (C3bi receptor), and CD16 (receptor for the Fc portion of IgG) antigens could differentiate the subsets. The killer phenotype was HLAlo, CD11bvery hi, and CD16very lo; the binder phenotype was CD11bhi and CD16lo; and the free-cell phenotype was CD11blo and CD16hi. Cell activation was not requisite for lytic function because no difference in either expression of activation markers or cell cycle could be established among the sorted subpopulations. Although recycling function was inhibited, retention of lytic activity was enriched 4-fold in the sorted killer cell population. These results represent characterization of a successful bulk isolation of competent killer, nonkiller binder, and free cells in human NK-cell populations and should aid our understanding of NK-cell development, lineage, and function.

Cytoplasmic components of natural killer cells limit the growth of Cryptococcus neoformans

Murine natural killer (NK) cell-mediated inhibition of growth of a yeast-like target cell, Cryptococcus neoformans, was completely abrogated by blocking the effector cell secretory process with monensin. Therefore, further studies were performed to determine the ability of various cytoplasmic fractions of NK cells to mediate inhibition of cryptococcal growth. Percoll-fractionated homogenates of rat LGL tumor cells demonstrated that the granule-containing fractions plus three additional sets of less dense cytoplasmic fractions displayed anti-cryptococcal activity; whereas only the cytoplasmic granule-containing fractions had cytotoxic activity against YAC-1 tumor cell and sheep erythrocyte targets. Maximal cryptococcal growth inhibition induced by LGL granules occurred after a 1 h incubation, required the presence of Ca2+ (1.0 mM) or Mg2+ (0.5 mM or 5.0 mM), and was completely abrogated in the presence of rabbit anti-LGL granule IgG. Cytolysin, the granule component which mediates tumor cell and sheep erythrocyte lysis, effectively limited the growth of cryptococci. Since Percoll gradient fractionation of the LGL homogenates demonstrated three separate peaks of anti-cryptococcal activity other than the granule peak, it is possible that the cytolysin-containing granules are not the only subcellular component of NK cells playing a role in inhibition of C. neoformans growth.

Scanning electron microscopic study of natural killer cell-mediated cytotoxicity

The interaction between human natural killer (NK) cells and NK-susceptible target cells, as well as the mechanism involved in target cell lysis, were studied with scanning electron microscopy (SEM). Low density human peripheral blood lymphocytes, highly enriched with large granular lymphocytes (LGL), were used as effector cells, and K562-cells were used as NK-susceptible target cells. The surface features of LGL/NK cells were examined under SEM. In the area of interaction, NK/target-cell conjugates showed microvilli and/or filipodia, and extensive areas of intercellular contact. In addition, the effector cells in some NK/target-cell conjugates were polarized toward the target cell. Changes in target cell surface features included loss of microvilli, large surface blebs and the appearance of small pore-like lesions on the cell membrane. Our findings show that target cell lysis occurred by apoptosis and plasma membrane lesions analogous to those seen during complement-mediated cytotoxicity.

Characterization and utilization of a monoclonal antibody inhibiting porcine natural killer cell activity for isolation of natural killer and killer cells

A mAb, porcine NK-inhibitory mAb (PNK-I) that inhibits porcine NK activity without affecting antibody-dependent cellular cytotoxicity (ADCC) has been developed. PNK-I acts at the level of the effector cell and inhibition of NK activity is independent of complement. Inhibitory effects are seen against various human and murine NK-susceptible targets. Addition of PNK-I antibody up to 60 min after assay initiation was effective at inhibiting NK activity. Furthermore PNK-I does not inhibit E:T conjugation and inhibits during the Ca2(+)-dependent phase of NK cytolysis. PNK-I Ag is present on virtually all PBL showing a bimodal distribution with 74% "dim" and 15% "bright" by flow cytometry. Monocytes and granulocytes stain with an intermediate intensity with greater than 90% and 95% staining positively, respectively. F(ab')2 fragments of PNK-I antibody show identical staining and functional activity as the whole molecule indicating that PNK-I acts independently of FcR. PNK-I immunoprecipitates molecules of molecular mass of 166, 155, 95 kDa under reducing and nonreducing conditions. PNK-I appears to be recognizing an epitope on a CD18 molecule. The CD18 molecule (beta-chain of CD11a,b,c) is ubiquitous on the surface of leukocytes and is implicated in a variety of cellular functions. Dim and bright populations were sorted and assessed functionally for NK and ADCC activity. It is demonstrated that PNK-I+ bright lymphocytes contain all detectable NK and ADCC activity in porcine PBL. Furthermore PNK-I+ bright lymphocytes contain the cytokine responsive NK cells capable of stimulation by IL-2, porcine NK-activating factor, and porcine natural killer-enhancing mAb. PNK-I+ dim cells were devoid of all baseline as well as inducible NK and ADCC activity. Giemsa stain of sorted populations show PNK-I+ bright cells containing the large granular lymphocytes whereas dim are devoid of these. Two color analysis show that PT4+ cells are PNK-I+ dim whereas PT8+ lymphocytes are divided between PNK-I+ bright and dim populations. Our results indicate that we are able to isolate all active as well as inducible NK and ADCC effector cells from porcine PBL based on relative Ag expression of CD18. Therefore quantitative as well as qualitative antigen expression is important in NK/ADCC-mediated cytotoxicity.

Morphometric evaluation of CD16-positive cells with respect to CD2 antigen coexpression

We examined morphometric as well as functional characteristics of CD16-positive human peripheral blood lymphocytes on the basis of the coexpression of the CD2 antigen. For morphometric analyses, nuclear area and cellular area were determined by counting line cross-points of a superimposed quadratic lattice test system overlying nuclei and the whole cell, respectively. Moreover, to evaluate the cellular villousity degree, the maximum inscrible circle and an irregular polygon were inscribed within cell profiles. The cytoplasm fraction included between the plasmalemma and the traced irregular polygon was considered as the villous portion of the cell. Finally, the NK capability was measured in a 6-hr 51Cr-release assay with human K-562 myeloid cells as targets. Within the CD16-positive cell population, the CD16-positive/CD2-negative cells seem to represent the most efficient NK cell subset. To the higher NK capability correspond a higher villousity degree and a lower nuclear area/cellular area ratio of the CD2-negative/CD16-positive subset, when compared with CD2-positive/CD16-positive cells.

Enhancement of human natural killer cell cytotoxicity by serotonin: role of non-T/CD16+ NK cells, accessory monocytes, and 5-HT1A receptors

Serotonin (10(-4) - 10(-7) M) augmented natural killer cell cytotoxicity (NKCC) of human CD16+/non-T lymphocytes in vitro against the NK-sensitive target cells K 562 erythroleukemic, Molt-4 lymphoma, Chang liver cells, and against EBV-transformed Daudi B-lymphoblastoid target cells by a mechanism of action involving a prostaglandin-and IL-1-independent accessory function of monocytes. No evidence for the production of intermediary, NK-enhancing cytokines by serotonin was obtained, suggesting a cell-to-cell-mediated interaction between monocytes and NK cells as a plausible mechanism of action for the NK-augmenting effect. Monocytes recovered by counter-current centrifugal elutriation but not monocytes recovered by adherence reconstituted the effect of serotonin when added to nonadherent NK cells. NK-enhancing effects of serotonin were mimicked by two 5-HT1A-type serotonin receptor agonists, 8-OH-DPAT and (+)-ALK. The development of NKCC in response to serotonin could be resolved into (i) an induction phase, dependent on the presence of accessory monocytes and serotonin, and (ii) an effector phase, independent of the presence of monocytes or serotonin. Serotonin-activated MNC continued to exert augmented cytotoxicity for at least 8 hr after the removal of serotonin and monocytes. In several experiments, serotonin-activated NK cells killed greater than 75% of K 562 target cells even at low effector to target cell ratios and low baseline NKCC. We suggest that serotonin may have a role in nonspecific tumor defence by regulating an earlier unrecognized interplay between monocytes and NK cells.

A morphological study of membrane lesions during natural killer-mediated lysis

Early and late events occurring during cell-mediated cytolysis have been examined ultrastructurally using transmission, scanning and freeze-fracture electron microscopy. K562 erythroleukemic cells were used as target for human natural killer lymphocytes, a subpopulation involved in host defense against tumor, virus infected and allogeneic cells. Cell binding between target and effector is already evident after 15 min, but membrane lesions and target hydration appear after 30 min incubation. At 60 min K562 cells appear swollen and microvilli-deprived. Progressive membrane disruption is also evident and the underlying cytoplasmic material is clearly exposed after 120 min. Submicroscopic membrane lesions appear to be early events in comparison with 51Cr (isotope) release from damage cells.

Effects of bacterial lipopolysaccharide and calmodulin on Ca2(+)-ATPase and calcium in human natural killer cells, studied by a combined technique of immunoelectron microscopy and ultracytochemistry

Our previous studies indicate that bacterial lipopolysaccharide (LPS) enhances natural killer (NK) cell-mediated cytotoxicity and increases intracellular calcium (Ca2+) in hepatocytes. Calmodulin (CAM) regulates Ca2(+)-ATPase activity, intracellular Ca2+, and is also implicated in NK cell-mediated cytolysis. In the present work, the effects of LPS and CAM on Ca2(+)-ATPase and intracellular Ca2+ in human NK cells were studied by a combined technique of immunogold electron microscopy and ultracytochemistry. Peripheral blood mononuclear cells were treated with 100 micrograms/ml E. coli (0111:B4) LPS and/or 5 micrograms/ml CAM in RPMI 1640 medium at 37 degrees C for 1 or 4 hr. NK cells labeled with monoclonal anti-Leu-11a (CD16) antibody and colloidal gold-conjugated anti-mouse IgG were processed for cytochemical localization of Ca2(+)-ATPase and Ca2+. Ca2(+)-ATPase was localized in the plasma membrane of NK cells, and its activity was suppressed by LPS but was enhanced by CAM. However, no apparent changes in the enzyme reaction were observed when cells were exposed to CAM concomitantly with LPS or stimulated with LPS before CAM. Apparent reduction of the enzyme reaction was observed when LPS stimulation was preceded by CAM. Ca2(+)-ATPase reaction in mitochondria was observed only in NK cells exposed to CAM. Computer image analysis showed no changes in the intracellular Ca2+ in NK cells treated with LPS for 1 hr, whereas a significant increase in Ca2+ was found in cells exposed to LPS for 4 hr. The intracellular Ca2+ significantly decreased in NK cells treated with CAM or with a combination of LPS and CAM as compared to that of controls (p less than 0.05). The results indicate that CAM is capable of blocking or reversing the inhibitory effect of LPS on Ca2(+)-ATPase, and suggest that in human NK cells the plasma membrane-associated Ca2(+)-ATPase is responsible for extrusion of intracellular Ca2+.

Anti-CD3 monoclonal antibody-mediated cytotoxicity occurs through an interleukin-2-independent pathway in CD3+ large granular lymphocytes

The mechanism of induction of cytotoxicity produced by anti-CD3 monoclonal antibody (MoAb) was studied in four patients with CD3+ large granular lymphocyte (LGL) leukemia. Anti-CD3 MoAb treatment resulted in increased target cell binding and increased granule formation. After activation, leukemic LGL remained Tac-, with the exception of a patient with CD4+ LGL leukemia. Radiolabeled interleukin-2 (IL-2) binding studies demonstrated that treatment with anti-CD3 MoAb resulted in upregulation of the number of p75 intermediate affinity IL-2 receptor sites per cell. Northern blot hybridization analysis showed expression of gamma-interferon gene transcripts 24 to 48 hours after activation. There was no evidence for expression of IL-2 messenger RNA or secretion of IL-2 after activation. Anti-CD3 MoAb and IL-2 provide different signals for activation of CD3+ LGL. Induction of cytotoxicity produced by anti-CD3 MoAb in leukemic CD3+ LGL is not associated with IL-2 production.

Liver-associated large granular lymphocytes: morphological and functional aspects

Large granular lymphocytes (LGLs) differ from other lymphocytes in their recirculation pattern and are distributed preferentially in nonlymphoid organs such as the liver and lung. The liver-associated LGLs adhere strongly to the sinusoidal endothelium and show a natural killer (NK) cytotoxicity against incoming metastatic tumor cells; this reaction occurs very rapidly because, in contrast to the immune response, it does not require complex processes in the lymphoid tissue. They have been extensively studied morphologically in terms of pit cells. LGLs have two characteristic cell organelles which participate in the NK cytolysis, i. e., dense granules and rod-cored vesicles. The former are lysosomes derived from multivesicular bodies and contain pore-forming proteins. The latter are the secretory vesicles exclusively seen in LGLs and are markedly increased in number when the NK function is augmented by biological response modifiers. These two structures are believed to be exocytosed in the space between LGL and the conjugated tumor cell. The microenvironment of the liver sinusoids, which includes Kupffer cells, endothelial cells and other lymphocytes, is considered to regulate the function of the liver-associated LGLs. Liver-associated LGLs, as well as Kupffer cells, are intrinsically involved in the defense system of the liver under various physiological and pathological conditions.