Inverted channel variations identified on a distal portion of a bajada in the central Atacama Desert, Chile.

In deserts, the interplay between occasional fluvial events and persistent aeolian erosion can form composite modern and relict surfaces, especially on the distal portion of alluvial fans. There, relief inversion of alluvial deposits by differential erosion can form longitudinal ridges. We identified two distinct ridge types formed by relief inversion on converging alluvial fans in the hyperarid Chilean Atacama Desert. Although they are co-located and similar in scale, the ridge types have different ages and formation histories that apparently correspond to minor paleoclimate variations. Gravel-armored ridges are remnants of deflated alluvial deposits with a bimodal sediment distribution (gravel and sand) dated to a minor pluvial phase at the end of the Late Pleistocene (~12 kyr). In contrast, younger (~9 kyr) sulfate-capped ridges formed during a minor arid phase with evaporite deposition in a pre-existing channel that armored the underlying deposits. Collectively, inverted channels at Salar de Llamara resulted from multiple episodes of surface overland flow and standing water spanning several thousand years. Based on ridge relief and age, the minimum long-term deflation rate is 0.1-0.2 m/kyr, driven primarily by wind erosion. This case study is an example of the equifinality concept whereby different processes lead to similar landforms. The complex history of the two ridge types can only be generally constrained in remotely sensed data. In situ observations are required to discern the specifics of the aqueous history, including the flow type, magnitude, sequence, and paleoenvironment. These findings have relevance for interpreting similar landforms on Mars.

The pathophysiology of the hairy cell.

HCs are clonal late B cells that are related to memory cells and display specific features of activation. Many of the distinctive features of HCs (eg, morphology, TRAP) are related to this specific activation. Many of the distinctive histologic features of HCL can be related to constitutive production of cytokines (eg, FGF, fibrosis) and to the expression/activation of adhesion receptors (eg, alpha(4)beta(1), alpha(5)beta(1) and alpha(v)beta(3) integrins, CD44v3). HCs usually have mutated IGVH genes and have no consistent or specific chromosome abnormalities (5q additions and 7q deletions in a minority). The signals that are responsible for several of the phenotypic features of HCs have been identified, but the nature of the underlying oncogenic events remains unknown.

Autocrine VEGF mediates the antiapoptotic effect of CD154 on CLL cells.

CD154 is an important regulator of chronic lymphocytic leukaemia (CLL)-cell survival. In CLL, high serum levels of VEGF are a feature of advanced disease, and we and others have previously shown that CLL cells produce and secrete this growth factor. Since CD154 stimulates VEGF production in other cell types, and VEGF is known to promote cell survival, we examined whether the cytoprotection of CLL cells by CD154 involves VEGF. We report for the first time that treatment of CLL cells with CD154 results in increased VEGF production and demonstrate involvement of NF-kappaB in this process. Moreover, we show that CD154-induced CLL-cell survival is reduced by anti-VEGF-neutralising antibody and by inhibiting VEGF receptor (VEGFR) signalling with SU5416. However, addition of exogenous VEGF alone or blocking secreted autocrine VEGF had little or no effect on CLL-cell survival. We therefore conclude that CLL-cell cytoprotection in the presence of CD154 requires combined signalling by both CD40 and VEGFR. This combined signalling and resulting cytoprotection were shown to involve NF-kappaB activation and increased survivin production. In conclusion, our findings identify autocrine VEGF as an important mediator of the antiapoptotic effect of CD40 ligation, and thus provide new insights into CLL-cell rescue by CD154 in lymphoreticular tissues.

Role of poly(ADP-ribosyl)ation in the killing of chronic lymphocytic leukemia cells by purine analogues.

Although the nucleoside analogues fludarabine and chlorodeoxyadenosine have become important therapeutic agents in chronic lymphocytic leukemia (CLL), their effectiveness is limited by drug resistance. Because such resistance is likely to result from impaired drug-induced apoptosis, it is clearly important to understand the mechanisms involved in this process. Whereas p53 can contribute to the nucleoside-induced killing of CLL cells, recent work from this laboratory and elsewhere has shown that such killing can also occur by p53-independent mechanisms. Because poly(ADP-ribose) polymerase (PARP)-mediated NAD+/ATP depletion has been implicated in the nucleoside-induced killing of normal resting lymphocytes, we postulated that this mechanism might account for the p53-independent component of nucleoside cytotoxicity in CLL. To address this question, we used 3-aminobenzamide (3AB) at a concentration (200 microM) known to produce selective inhibition of poly(ADP-ribosyl)ation in intact cells and examined nucleoside-induced killing using a number of different end points (cell membrane disruption, cell shrinkage, mitochondrial depolarization, exposure of phosphatidyl serine, morphological changes, DNA fragmentation, and PARP-1 cleavage). In 27 of the 30 cases of CLL examined, 3AB delayed nucleoside-induced cell membrane disruption without inhibiting other manifestations of cytotoxicity. This indicates that PARP activity, rather than contributing to the induction of cell killing, was accelerating cell membrane disruption during the late stages of apoptosis. This novel observation has important implications for previous studies of PARP-mediated cytotoxicity. However, in cells from one CLL patient, 3AB inhibited all manifestations of nucleoside cytotoxicity; this was the only case in the study known to have a p53 gene defect affecting both alleles. This indicates that PARP activity can occasionally be central to nucleoside-induced killing and that such PARP-mediated killing is p53 independent.

The role of hyaluronan and interleukin 8 in the migration of chronic lymphocytic leukemia cells within lymphoreticular tissues.

Malignant lymphocyte migration into and within lymphoreticular tissue is an important aspect of chronic lymphocytic leukemia (CLL), yet little is known about the processes involved. Our previous studies of integrin expression and function in CLL have shown that the abnormal cells are relatively nonadhesive and nonmotile on the protein ligands of these receptors. Here we show that CLL cells adhere to a non-protein ligand, hyaluronan (HA), and become motile (as assessed by both Boyden chamber migration and time-lapse video microscopy) on this ligand when stimulated with interleukin (IL) 8. The combined presence of HA and IL-8 was essential for this motility because IL-8 did not stimulate movement on other surfaces. Blocking antibodies showed that this motility is mediated by the receptor for HA-mediated motility (RHAMM), without the involvement of CD44. Moreover, confocal microscopy showed a polarized distribution of RHAMM and F-actin, but not CD44, in cells which had become motile on HA in the presence of IL-8. Immunohistochemical studies of nodes and spleen demonstrated an abundant reticular network of HA-containing fibers throughout diseased nodes and in splenic white pulp. The splenic red pulp and the luminal surface of high endothelial venules lacked HA. IL-8 was ubiquitously present in these tissues. CLL cells were shown to move spontaneously on fibroblast monolayers derived from lymphoid tissue; this movement was largely blocked by hyaluronidase or anti-RHAMM or anti-IL-8 antibodies. These studies indicate that IL-8-induced motility on HA is likely to be important for CLL cell migration through lymphoid tissue.

The beneficial effects of alpha-interferon in hairy cell leukemia are not attributable to NK cell-mediated cytotoxicity.

The natural killer (NK) activity of peripheral blood mononuclear cells against K562 targets was variable in 10 untreated patients with hairy cell leukemia and was inversely related to the number of hairy cells (HCs) present. After therapy with alpha-interferon (IFN-alpha) NK activity in vitro was equivalent to that of normal controls. It is suggested that the low activity often seen before treatment is attributable to dilution of NK cells by large numbers of inactive HCs and that this diluting effect is reduced as HCs disappear from the blood during IFN-alpha treatment. HCs was consistently resistant to NK lysis by normal or hairy cell leukemia allogeneic and autologous mononuclear cells, despite whether effector or target cells had been pretreated with IFN-alpha. Cold-target inhibition and direct binding experiments showed that HCs do not bind to NK effectors. It is therefore concluded that NK cells play no direct role in the progressive disappearance of HCs seen in patients receiving IFN-alpha.

Alpha-interferon and lymphokine-activated killer cells in hairy cell leukemia.

Lymphokine-activated killer (LAK) cell activity generated from peripheral blood was tested in 6 patients with typical hairy cell leukemia, 3 not on treatment with alpha-interferon (alpha-IFN) and 3 receiving therapy. In all cases, substantial killing of the LAK-sensitive target Daudi was observed, but hairy cells, whether or not they had been pretreated with alpha-IFN, were uniformly resistant to LAK lysis. The hairy cells were also resistant to LAK cell killing generated from normal peripheral blood mononuclear cells. alpha-IFN added at various times during LAK generation had little or no effect on LAK activity. It is concluded that LAK cells are not important in mediating the beneficial effects of alpha-IFN in hairy cell leukemia.

The effect of cytokines, including IL-1, IL-4, and IL-6, in hairy cell proliferation/differentiation.

IL-1, IL-4, and IL-6 had no effect on hairy cell (HC) proliferation in vitro. Anti-mu and low molecular weight B cell growth factor (LBCGF) and tumor necrosis factor alpha (TNF-alpha) stimulated the proliferation of a minor subpopulation of HCs detected by double immunocytochemical staining. None of these cytokines had any effect on HC differentiation as measured by immunoglobulin secretion. It is concluded that none of the above growth factors are central to HC proliferation in-vivo. Since alpha-interferon IFN-alpha, but not IFN-gamma, consistently inhibited any proliferation observed, it seems likely that this monokine has a direct antiproliferative effect in vivo.

Hairy cells possess more interferon receptors than other lymphoid cell types.

To investigate the possible direct effects of alpha-interferon (IFN-alpha) in hairy cell leukemia, IFN-alpha receptor expression by hairy cells (11 cases) was measured by a radiolabeling technique and compared with that of MOLT-4, chronic lymphocytic leukemia (15 cases), and various other leukemic and normal cell types. Purified peripheral blood and splenic hairy cells showed higher levels of receptor expression (approximately 1,000 +/- 200 binding sites/cell; 11 cases tested) than other normal and leukemic cell types. B cells from normal blood and tonsils showed low levels of receptors (approximately 120 +/- 100 binding sites/cell), while a range of B cell leukemias displayed intermediate levels of expression (100-500 sites/cell). In the 15 cases of chronic lymphocytic leukemia tested, 530 +/- 330 binding sites/cell) were demonstrated, the high standard deviation reflecting the fact that one third of cases had receptor levels comparable with those in hairy cell leukemia. Normal and hairy cell leukemia T cells, red cells, and platelets had no demonstrable IFN-receptors. These findings may be relevant to the efficacy of IFN in hairy cell leukemia.

The U.K. experience with human lymphoblastoid interferon in HCL: a report of the first 50 cases.

The results of treatment of the first 50 patients with hairy cell leukemia given human lymphoblastoid alpha-interferon (Wellferon) are presented. All patients, irrespective of previous splenectomy or splenomegaly showed evidence of response. Side effects were minor. Surface marker studies provided no clear indication of the mechanism of action of alpha-interferon. It is concluded that Wellferon is highly effective in this disease.

Sequential potentiation and inhibition of PMN reactivity by maximally stimulated platelets.

In a recent study, we showed that granulocyte-macrophage colony-stimulating factor (GM-CSF) and supernatants from partially stimulated platelets undergoing selective alpha-granule release synergistically enhanced polymorphonuclear leukocyte (PMN) response to N-formyl-methionyl-leucyl-phenylalanine (fMLP). The active factor released from platelet alpha-granules was identified as platelet factor four (PF4). In this study we investigate the joint effect on PMN reactivity of GM-CSF and supernatants from platelets maximally stimulated to release both alpha- and dense granule contents. These platelet supernatants enhanced PMN chemiluminescence (CL; a measure of the oxidative burst) during short incubations, whereas longer incubations led to the loss of this enhancement and the prevention of PMN priming by GM-CSF. The platelet-derived inhibitory factor was of low molecular weight, originated from the dense granule precursor(s), and its generation required the presence of PMN. When ATP/ADP were incubated with PMN at concentrations found in platelet-dense granules, they produced a similar biphasic effect on PMN reactivity (a potentiation followed by inhibition) as seen with the platelet supernatants. The inhibitory effect of these nucleotides coincided with their conversion to AMP. AMP per se had an immediate inhibitory effect on PMN response to fMLP and prevented PMN priming by GM-CSF. This study confirms that partially stimulated platelets enhance PMN reactivity. However, during maximal stimulation, nucleotides released from the platelet-dense granules are converted to AMP, which in turn can counteract the PMN priming effects of factors such as PF4 and GM-CSF.

Peanut agglutinin in combination with CD19 monoclonal antibody has potential as a purging agent in myeloma.

Administration of high-dose chemotherapy to patients with myeloma, followed by rescue with autologous bone marrow transplantation (ABMT), sometimes induces complete disease remission but relapse is usual. We have attempted to reduce the risk of relapse by selective in vitro removal of myeloma cells from the autologous graft. A combination of the (gal-galNac)-binding lectin peanut agglutinin (PNA), which binds all plasma cells, and the pan-B monoclonal antibody CD19 was assessed for purging marrow of myeloma cells and their putative precursors using a magnetic bead method. Preliminary experiments performed on peripheral blood mononuclear cells spiked with fluorescent-labeled PNA+ Kirk tumor cells showed that a magnetic bead: target cell ratio of 40:1 resulted in a greater than 3-log reduction in PNA+ cells. This technique was then applied to 17 samples of myeloma bone marrow and to 18 samples of normal bone marrow spiked with PNA+ Kirk cells and CD19+ hairy cell leukemia cells. In each case all detectable plasma cells and CD19+ lymphocytes were effectively removed, and normal hemopoietic progenitor cell recovery was greater than 55%. This purging system deserves further study as a means of reducing relapse rates in myeloma patients treated by a combination of high-dose chemotherapy and ABMT.

The diagnosis and treatment of hairy-cell leukaemia.

The diagnosis of HCL is usually straightforward and is based on the identification of typical HCs in the blood and bone marrow. The suspected diagnosis is confirmed by a combination of TRAP cytochemistry, a distinctive immunophenotype and characteristic BM trephine appearances. Nucleoside treatment is highly effective in inducing prolonged remissions; relapsing patients can usually be successfully retreated with nucleoside. Monoclonal antibody therapy is a promising novel approach to the treatment of resistant disease.

The current status of interferon alpha in haemic malignancy.

Interferon-alpha (IFN alpha) has been extensively studied, both in clinical trials and in the laboratory. The cytokine has proved most effective in haemic malignancy, in particular hairy cell and chronic granulocytic leukaemia. This article deals with the current status of IFN alpha in these conditions and the possible basis of this sensitivity. Other less responsive haemic malignancies are also discussed.

The biology of hairy cells.

The evidence that hairy cells are activated clonal late B cells is presented. The largely non-specific (i.e. not confined to hairy-cell leukaemia) chromosome and genetic abnormalities are then described. Next, the features of malignant-cell activation are considered, including the distinctive morphology of hairy cells and their expression of activation-related antigens and activated adhesion receptors. Also, signalling and cytokine production are discussed in the context of malignant-cell activation. It is then demonstrated that many of the distinctive clinicopathological features of hairy-cell leukaemia can be explained in terms of the interaction of the activated malignant cells with other types of cell and tissue matrix. Finally, the biological basis of the hairy cell's unusually high sensitivity to IFN-alpha and nucleoside analogues is discussed.

Stimulated lymphoid cells of B lineage, but not plasma or myeloid cells, can express E receptor.

After culture with 20-30% autologous or allogeneic T cells and PHA, at least a proportion of the pathological cells from a variety of B-cell proliferations (common acute lymphoblastic leukaemia, prolymphocytic leukaemia, non-Hodgkin's lymphoma with blood involvement by mature lymphoid (cleaved and non-cleaved) cells) expressed true endogenous sheep erythrocyte (E) receptors. In contrast, plasma cells and a variety of myeloid cells failed to express E receptors after similar in vitro stimulation. These data, taken in conjunction with previous findings with B cells from normals and patients with hairy-cell and chronic lymphocytic leukaemia, suggest that B cells earlier than plasma cells can express E receptors after appropriate stimulation. The findings provide an in vitro counterpart of the leukaemic proliferations expressing both E receptor and surface immunoglobulin described from various laboratories, and further question the lineage specificity of the E receptor.

The effects of alpha interferon on human long-term bone marrow culture.

The effect of alpha IFN on normal long term bone marrow culture (LTBMC) was assessed by measuring haemopoietic progenitor formation and stromal cell number and composition over the course of 5 weeks. When alpha IFN was added at the initiation of LTBMC, there was a marked inhibition of CFU-GEMM, BFU-E and CFU-GM formation from both adherent and non-adherent compartments of culture. There was a profound inhibition of stromal layer formation, especially the reticulo-fibroblast component, and this was not a result of TNF release from macrophages. When alpha IFN was added to established normal LTBMC, although haemopoietic progenitor formation was inhibited, there was little effect on the stromal layer in terms of number or composition. This suggests that the cytostatic effects of alpha IFN when added at commencement of LTBMC result from the anti-proliferative effects of alpha IFN on these actively dividing cells. It is concluded that in addition to the established inhibitory effects of alpha IFN on haemopoietic progenitors as previously demonstrated in semi-solid culture systems, alpha IFN has profound effects upon the marrow microenvironment. This is of particular relevance to bone marrow transplantation where such cytokines may be considered for clinical use.

Suppressor T cells in B-cell chronic lymphocytic leukaemia: relationship to clinical stage.

In 32 patients with B-cell chronic lymphatic leukaemia (CLL), OKT8+ suppressor T cells were increased in relative (mean 54 +/- 14%; normal mean 34 +/- 6%) and absolute (1.8 +/- 1.6 X 10(9)/1; normal range 0.3-0.6 X 10(9)/1) numbers. OKT4+ helper cells were reduced in relative (mean 53 +/- 15%; normal mean 65 +/- 7%) but not absolute (1.7 +/- 1.4 X 10(9)/1; normal range 0.6-1.4 X 10(9)/1) numbers. Essentially identical results were obtained in treated and untreated patients. There was no significant association between T-cell subset numbers and clinical stage, whether assessed by the Rai classification or the more recent Binet system, although the OKT4+/8+ ratio was slightly lower in advanced disease. The study suggests that the immunoparesis so characteristic of CLL may be attributable to increased suppressor T-cell activity.

Homotypic interactions protect chronic lymphocytic leukaemia cells from spontaneous death in vitro.

Chronic lymphocytic leukaemia (CLL) cells are long-lived in vivo but undergo spontaneous apoptosis when cultured in vitro. Since CLL cells associate intimately with one another at sites of tissue involvement, we examined the hitherto unproven possibility that homotypic interactions between the malignant cells might reduce their propensity to undergo spontaneous cell death. In a series of experiments in which highly pure CLL-cell populations were cultured on a non-adherent surface, cell viability was found to increase markedly with the level of crowding at the bottom of the culture vessel. The effect was observed among unevenly distributed cells within a single culture vessel and did not require direct cell-cell contact. This indicates that cell survival was being regulated in an autocrine fashion by locally acting soluble products. Conditioned medium from crowded CLL cells enhanced the survival of autologous non-crowded cells, indicating that at least some of the autocrine survival factors produced by CLL cells could accumulate in the extracellular environment. In addition, the survival of non-crowded CLL cells was markedly enhanced by co-culturing them with an excess of autologous fixed cells. This protective effect of direct cell-cell contact was mediated by specific surface structures since it was abrogated by pre-treating the fixed cells with neuraminidase. Our results provide the first direct demonstration that the survival of cultured CLL cells is enhanced by homotypic interactions. We speculate that these protective effects may contribute to the accumulation of CLL cells in vivo, and that further elucidation of the underlying mechanisms may lead to novel therapeutic strategies.

Alpha-interferon in myelodysplasia; clinical observations and effects on NK cells.

A total of 15 patients with myelodysplastic states (MDS) were studied. Of the eight patients treated with alpha-interferon (alpha IFN) (3 megaunits/day for up to 6 months), one patient with refractory anaemia with excess blasts (RAEB) underwent an almost complete response while one case of chronic myelomonocytic leukaemia (CMML) showed a reduction in monocyte count; no improvement was observed in refractory anaemia (RA) or refractory anaemia with excess blasts in transformation (trRAEB). In all patients Leu7+ and Leu11a+ phenotypic natural killer (NK) cells were consistently normal in percentage numbers but functional NK activity was consistently reduced in all MDS subgroups. NK activity was enhanced by exposure to alpha IFN in vitro, but was very variable in patients being treated with the agent. There was no correlation between clinical response and changed NK activity in patients receiving alpha IFN. It is concluded that NK cells are unlikely to play a central role in the biology of myelodysplasia.