Involvement of CD31 in lymphocyte-mediated immune responses: importance of the membrane-proximal immunoglobulin domain and identification of an inhibiting CD31 peptide

CD31 (PECAM-1) is an immunoglobulin gene superfamily cell adhesion molecule found on vascular endothelium, platelets, and leukocytes. Lymphocyte expression of CD31 is most closely associated with the CD45RA+CD8+ naive T phenotype. CD31 has recently been shown to play a role in leukocyte egress to inflammatory sites. The mechanism of CD31 adhesion remains under investigation. Several investigators have reported evidence for a heterotypic ligand. We have previously shown that CD31 is phosphorylated with cell activation, which suggests a possible role for CD31 in cell activation events. We therefore studied the effects of CD31 antibodies on in vitro assays of lymphocyte activation. One CD31 antibody, LYP21, inhibited the mixed lymphocyte reaction (MLR) in a specific and dose-dependent fashion. An LYP21 epitope was localized to the sixth Ig domain of CD31. This peptide and a scrambled control peptide were synthesized and used to study effects of this epitope on lymphocyte activation. The CD31 peptide strongly inhibited the MLR. Because CD31 is expressed on both stimulator and responder populations, stimulator peripheral blood leukocytes and responder lymphocyte populations were separately incubated with CD31 peptide or control peptide and then washed before mixing. The CD31 peptide inhibited the MLR equally when either stimulator or responder cells were preincubated with the CD31 peptide. We further sorted responder cells into CD31-high and CD31-low populations and separately incubated these subsets with peptides. The CD31 peptide strongly inhibited MLRs, regardless of level of responder-cell CD31 expression. Examination of MLR reactions involving the CD31 peptide showed dispersed small aggregates of cells, rather than the single large aggregate observed in control MLRs. The CD31 peptide did not affect activation of lymphocytes by phorbol myristate acetate (PMA) and ionomycin. These results suggest that a surface CD31-ligand interaction may have a functional role in alloimmune lymphocyte activation and identify a functionally important domain of CD31.

The cell adhesion molecule CD31 is phosphorylated after cell activation. Down-regulation of CD31 in activated T lymphocytes

We report the independent cloning of the cDNA for CD31, a recently described cell adhesion molecule of the immunoglobulin gene superfamily present on platelets, granulocytes, monocytes, lymphocytes, and endothelial cells. Northern analysis revealed three major mRNA transcripts in Jurkat (a human T cell line) and K562 and HEL (leukemia cell lines) cells with an additional 5.3-kilobase transcript seen in cultured human umbilical vein endothelial cells. Following T cell activation, CD31 mRNA was down-regulated by Northern analysis, and decreased CD31 protein expression was confirmed by immunoblots. The down-regulation of CD31 was partially mediated by decreased transcription as demonstrated by nuclear run-on studies. CD31 became rapidly phosphorylated in platelets, Jurkat cells, and endothelial cells after cell activation. We were unable to demonstrate the presence of a phosphotyrosine in CD31 using monoclonal and polyclonal phosphotyrosine antibodies. In addition, CD31 phosphorylation in platelets was induced by phorbol ester and was blocked by staurosporin, a protein kinase C inhibitor, suggesting that CD31 phosphorylation is mediated by protein kinase C and involves serine and/or threonine residues. The phosphorylation of CD31 following cell activation may modulate its cellular adhesiveness, and the down-regulation of its expression may serve to impart target specificity and to localize effector lymphocytes to areas of inflammation.

Treatment of adult acute lymphoblastic leukemia with intensive cyclical chemotherapy: a follow-up report

We treated 109 patients with adult acute lymphoblastic leukemia (ALL) diagnosed by histochemical and immunologic techniques. Patients were excluded only for age greater than 50 years and Burkitt's leukemia. Treatment included a four-drug remission induction phase followed by alternating cycles of noncrossresistant chemotherapy and prolonged oral maintenance therapy. Eighty-eight percent of patients entered complete remission. With a median follow-up of 77 months (range, 48 to 111 months), 42% +/- 6% (SEM) of patients achieving remission are projected to remain disease-free at 5 years, and disease-free survival for all patients entered on study is 35% +/- 5%. Failure to achieve remission within the first 4 weeks of therapy and the presence of the Philadelphia chromosome are associated with a 100% risk of relapse. Remission patients with neither of these adverse features have a 48% +/- 6% probability of remaining in continuous remission for 5 years. Patients with T-cell phenotype have a favorable prognosis with 59% +/- 13% of patients achieving remission remaining disease-free compared with 31% +/- 7% of CALLA-positive patients. Intensive chemotherapy may produce prolonged disease-free survival in a sizable fraction of adults with ALL. Improved therapy is needed, especially for patients with adverse prognostic features.

Production of granulocyte/macrophage-colony-stimulating factor by human natural killer cells. Modulation by the p75 subunit of the interleukin 2 receptor and by the CD2 receptor

Resting natural killer (NK) cells express the p75 chain of the IL-2 receptor (IL-2R beta) and most NK cells express the CD2 (erythrocyte rosette) receptor. The cell adhesion molecule, LFA-3, is a natural co-ligand for CD2. Tac antigen (IL-2R alpha), a p55 IL-2R subunit, can be expressed after NK activation and may play a role in IL-2-induced NK proliferation. Little is known of the molecular mechanisms underlying cytokine production in NK cells. We investigated the roles of IL-2R alpha, IL-2R beta, and CD2/LFA-3 in the molecular regulation of NK cell granulocyte/macrophage-colony-stimulating factor (GM-CSF) production. Enriched populations of peripheral blood NK cells were separated into CD16-positive and CD16-negative fractions by flow cytometry; positively selected cells were greater than 97% positive for CD16 (the FcIII receptor for IgG which is present on almost all NK cells), less than 1% positive for the T cell antigen CD3, and did not demonstrate rearrangement of the T cell receptor beta chain gene by Southern blot. NK cell supernatants were harvested after 3-4 d of incubation with 0-100 U/ml IL-2, or after incubation with anti-CD2 (T11(3] MAb and sheep red blood cells (SRBC are a homologue for LFA-3). Parallel cell aliquots were harvested at 3-16 h for transcriptional run-on assays, S1 nuclease assays, and actinomycin D mRNA t1/2 determinations. IL-2-activated NK supernatants contained large amounts of GM-CSF (178 +/- 35 pg/ml) by ELISA as did supernatants from CD2-activated NK cells (T11(3) MAb + SRBC: 212 +/- 42) vs. less than 20 pg/ml for NK cells incubated alone or with either SRBC or T11(3) MAb alone. Sepharose-linked anti-CD3 MAb did not induce GM-CSF release from NK cells. By S1 analysis, both IL-2 and CD2 stimulation markedly augmented GM-CSF mRNA expression but with very different latencies of onset. IL-2R beta MAb inhibited greater than 85% of GM-CSF release from IL-2-activated NK cells and markedly suppressed IL-2-induced GM-CSF mRNA expression, whereas IL-2R alpha MAb even at 2,000-fold molar excess of IL-2 had little effect (less than 10%) on either GM-CSF release or mRNA expression. Run-on assays showed that GM-CSF is constitutively transcribed in NK cells and that IL-2 and CD2-activated cells had a three- to fourfold increased rate of GM-CSF transcription compared to nonstimulated cells. The t1/2 of GM-CSF mRNA in IL-2-activated NK cells was identical to that of unstimulated NK cells (15 min), whereas GM-CSF mRNA t1/2 in CD2-activated NK cells was increased 2.5-fold. We conclude that GM-CSF production in NK cells is regulated by both the IL-2Rbeta and the CD2 receptor but not by IL-2Ralpha, that both transcriptional and posttranscriptional signals act together to modulate the level of GM-CSF mRNA in NK cells, and that the molecular mechanisms underlying NK cell GM-CSF production are dependent in part on differential surface receptor activation.

Interaction of histidine-rich glycoprotein with human T lymphocytes

Histidine-rich glycoprotein (HRGP), a human plasma and platelet protein, interacts with multiple ligands in vitro, including heparin, plasminogen, thrombospondin, and fibrinogen/fibrin. In this study, the binding of HRGP to human T lymphocytes was characterized. The binding was specific, concentration-dependent, saturable, and reversible. Scatchard plot analysis revealed two classes of binding sites: the high affinity class had an apparent dissociation constant (Kd) of 1.92 X 10(-8) M, with 0.92 X 10(4) sites/cell, and the low affinity class had a Kd of 4.97 X 10(-7) M, with 3.7 X 10(4) sites/cell. HRGP binding to T cells in the presence of HRGP-depleted serum was comparable to that observed in buffer. Dot-blot analysis showed that HRGP bound to specific T cell proteins. Using both HRGP affinity chromatography and immunoprecipitation with affinity-purified anti-HRGP IgG, a major 56-kDa HRGP-binding protein in surface labeled T cell lysates was demonstrated. The 56-kDa protein was shown not to be related to the CD2 molecule on T cells. The binding characteristics of HRGP to T lymphocytes indicate a specific ligand-receptor interaction. This is the first demonstration of HRGP binding to a cell surface, and its binding to human T cells may play an important role in T lymphocyte biology.

Histidine-rich glycoprotein blocks T cell rosette formation and modulates both T cell activation and immunoregulation

Histidine-rich glycoprotein (HRGP) is a plasma and platelet protein with undefined function in vivo. It has been reported to inhibit rosette formation between murine T cells and erythrocytes. We have shown that HRGP binds specifically to human T lymphocytes but not sheep erythrocytes and have demonstrated a 56-kDa HRGP-binding protein on the T cell surface which is distinct from the CD2 sheep erythrocyte receptor. We have now investigated whether HRGP can inhibit human T cell-sheep erythrocyte rosette formation and whether HRGP can modulate T cell activation. HRGP at physiologic concentrations specifically inhibited rosette formation between human T lymphocytes and sheep erythrocytes. HRGP suppressed proliferation of antigen receptor (CD3)-triggered T cells induced by interleukin 2; this suppression was specifically reversed by prior incubation of HRGP with affinity-purified anti-HRGP IgG. Addition of HRGP 12-24 h after CD3 triggering no longer suppressed T cell proliferation, suggesting HRGP suppressed T cell division by interfering with one or more early events in the process of T cell activation. Human serum (containing 100-150 micrograms/ml HRGP) was also capable of suppressing T cell proliferation; serum which had been immunodepleted of HRGP no longer inhibited T cell proliferation. Furthermore, HRGP inhibited interleukin 2 receptor expression on activated T cells, causing decreased T cell interferon-gamma release and altered T cell-dependent inhibition of erythropoiesis. HRGP is thus capable of modulating T cell activation and T cell immunoregulation; HRGP may function as a natural suppressive regulator of human T lymphocyte activation.

Bleeding diathesis due to decreased functional activity of type 1 plasminogen activator inhibitor

We evaluated an elderly patient with a lifelong history of severe bleeding after surgery or trauma and with evidence of persistent hyperfibrinolysis. Routine coagulation studies were normal. Serum plasminogen (40%, normal 72-128%) and alpha 2-antiplasmin (55%, normal 70-145%) activities were decreased. Euglobulin clot lysis was abnormally shortened (50 min) and normalized in vitro with epsilon-aminocaproic acid (EACA). The patient was treated with EACA with prompt cessation of bleeding. Patient tissue-plasminogen activator (t-PA) levels in serum were normal (4.7 ng/ml, control 3.5-7.2) as detected by a two-site immunoradiometric assay (IRMA). Patient fibrinolytic inhibitor activities were assessed by incubating 125I-labeled t-PA with either whole blood or serum followed by SDS-PAGE and autoradiography to identify the resultant protease/protease inhibitor complexes. In comparison to blood samples obtained from normal donors, patient plasma and serum demonstrated reduced binding of a fast-acting plasminogen activator inhibitor to 125I-labeled t-PA. Immunoprecipitation experiments indicated diminished complex formation between type 1 plasminogen activator inhibitor (PAI-1) in patient serum and 125I-labeled t-PA. Low patient PAI-1 activity was confirmed in serum (0.36 U/ml, control 0.87-1.81; n = 3) and in platelet lysates using a functional IRMA to quantitate PAI-1 binding to immobilized t-PA. However, patient serum PAI-1 antigen was within the normal range when analyzed by IRMA (31.8 ng/ml, control 19.6-42.2); this result was confirmed in both serum and platelets by Western blot (n = 3). Mixing experiments using purified PAI-1 as well as patient and control sera did not show evidence for an inhibitor against PAI-1. We conclude that this patient's bleeding diathesis was due to hyperfibrinolysis and defective PAI-1. This patient provides the first demonstration of a link between decreased in vivo PAI-1 activity and disordered hemostasis, and supports a role for PAI-1 in control of vivo fibrinolysis.

Human T cell leukemia virus-I-associated T-suppressor cell inhibition of erythropoiesis in a patient with pure red cell aplasia and chronic T gamma-lymphoproliferative disease

Human retroviruses have recently been linked with T cell lymphoproliferative disorders and with the acquired immune deficiency syndrome. We investigated the mechanisms for acquired pure red cell aplasia and cutaneous anergy in a patient with the chronic T gamma-lymphoproliferative disease (T gamma-LPD) syndrome. Patient marrow erythroid progenitors (BFU-E) were 17 +/- 9% of control and were selectively increased to 88-102% of control after marrow T cell depletion. Patient Leu 2+ suppressor T cells spontaneously produced high titers of human gamma-interferon and resulted in a concentration-dependent selective inhibition (74-91%) of BFU-E when co-cultured with autologous or allogeneic marrow. Conditioned media (CM) derived from patient Leu 2+ T cells similarly inhibited growth of autologous or allogeneic marrow BFU-E. The inhibitory factor derived from patient CM was acid-labile (pH 2) and sensitive to trypsin; prior treatment of patient T cells with anti-HLA-DR monoclonal antibody plus complement abrogated the suppressive effect of T cell-derived CM. Patient peripheral blood mononuclear cells (PBMC) were unable to support growth of cultured interleukin 2 (IL 2)-dependent T cells, but responded to exogenous IL 2 in vitro with a 16-21-fold augmentation, relative to control, in mitogen-induced proliferation. Antibodies to HTLV-I core proteins p19 and p24 but not to HTLV-III proteins were detected in patient serum by Western blotting; patient cultured PBMC stained (7-11%) with antibodies to p19 and p24. Patient cultured PBMC demonstrated integrated HTLV-I genomic sequences by the Southern technique and expressed both specific HTLV-I genomic sequences by RNA dot blot plus reverse transcriptase activity. Utilizing a cloned DNA probe for the beta chain of the T cell receptor gene, patient PMBC demonstrated gene rearrangements providing presumptive evidence for clonality. The presence in serum of HTLV-I p19 and p24 antibodies, the expression of p19 and p24 core antigens on patient mononuclear cells, the evidence of HTLV-I proviral integration sequences and the expression of HTLV-I genomic sequences in patient cells, indicates infection with HTLV-I and raises the possibility of an etiologic link between human retrovirus infection and some instances of large granular lymphocytic leukemia (T gamma-LPD).

Evans' syndrome as a presenting manifestation of atypical paroxysmal cold hemoglobinuria

Paroxysmal cold hemoglobinuria is a rare and potentially life-threatening acquired hemolytic anemia occurring either as an acute transient anemia following several different viral syndromes, or in a chronic idiopathic form. Episodic hemolysis in paroxysmal cold hemoglobinuria is usually associated with a biphasic (Donath-Landsteiner) IgG cold-reactive complement-fixing autohemolysin with anti-P specificity. Paroxysmal cold hemoglobinuria has not previously been associated with malignancy nor has it been clearly shown to be steroid-responsive. This report describes a patient with steroid-responsive autoimmune hemolytic anemia and immune thrombocytopenia (Evans' syndrome) associated with oat cell carcinoma of the lung and a unique biphasic anti-IgM autohemolysin. This case extends the spectrum of biphasic antibody-mediated immune cytopenias and widens both the clinical and the serologic definition of paroxysmal cold hemoglobinuria.

Receptor-specific inhibition of bone marrow erythropoiesis by recombinant DNA-derived interleukin-2

Interleukin-2 (IL-2) induces differential secretion of lymphokines by IL-2 receptor (IL-2R)-positive and IL-2R-negative T cells. We studied T cell IL-2R-specific modulation of adult bone marrow erythropoiesis by recombinant IL-2 (rIL-2). I3-2R were induced by CD3 T cell surface determinant-triggering and analyzed by cytofluorography. Bone marrow monocyte and T cell-depleted (NAB-T) target cells were assessed for early erythroid progenitor expression (BFU-E) in the presence of 0 to 10(3) U/mL of rIL-2, rIL-2 had no significant effect on BFU-E expression in the absence of T cells or in the presence of IL-2R-negative T cells. rIL-2 caused a dose-dependent inhibition (75% to 90%) of BFU-E in the presence of autologous IL-2R-positive T cells. The addition of anti-IL2-receptor antibody to cultures containing rIL-2 plus IL-2R-positive T cells entirely abrogated rIL-2-mediated inhibition of BFU-E. In the presence of rIL-2 (10(2) U/mL) production of interferon gamma (IF-gamma) by adult marrow CD3-triggered IL-2R-positive T cells was increased 37- to 125-fold compared to IL-2R-negative T cells. rIF-gamma caused a dose-dependent (88% +/- 17% at 10(3) U/mL) inhibition of adult BFU-E in the presence of CD3-triggered autologous T cells. rIL2-mediated inhibition of adult BFU-E in the presence of IL-2R-positive T cells was partially abrogated (52% +/- 16%) following addition of monospecific IF-gamma antibody. These results demonstrate (a) rIL-2 modulation of adult marrow erythropoiesis is selectively dependent upon both the presence or absence of autologous T cells and the IL-2R status of these T cells; and (b) rIL-2-induced inhibition of adult marrow erythropoiesis is mediated in part by release of IF-gamma from IL-2R-positive T cells.

Improved results of treatment of adult acute lymphoblastic leukemia

We designed a treatment program to improve the outcome for adults with acute lymphoblastic leukemia (ALL). Treatment included a remission-induction phase followed by intensive alternating cycles of non-cross-resistant chemotherapy and prolonged oral maintenance therapy. Eighty-one consecutive previously untreated patients were entered on this study. Ninety-four percent of patients entered complete remission. A Kaplan-Meier analysis predicts that 53% +/- 9% (SEM) of patients in remission will remain free of disease at 3 years. Neither age, sex, WBC count, nor immunophenotype had a significant effect on remission duration. This program of intensive cyclical chemotherapy has improved the disease-free survival of patients with adult ALL.

Chlorpropamide-induced pure white cell aplasia

We investigated the mechanism for isolated agranulocytosis and marrow pure white cell aplasia in an elderly man receiving 0.5 to 1.0 g per day of chlorpropamide (Chl) without other toxic drug exposure or overt systemic illness. Patient marrow revealed an absence of recognizable granulocytic precursors; megakaryocytes and erythroid precursors were normal. The WBC count was 1800/mm3 on admission with only 2% neutrophils; the absolute neutrophil count first exceeded 500/mm3 on the 17th day following cessation of Chl. A serum Chl level on admission was 100 micrograms/mL (acute phase, AP); no Chl was detected in serum (convalescent phase, CP) assessed on the 22nd hospital day. Antineutrophil antibodies were not detected, and T cell depletion failed to augment patient in vitro granulopoiesis. Patient AP serum produced potent complement-mediated inhibition (87% +/- 7%) of autologous granulocyte progenitors (CFU-GM) with minimal inhibition of erythroid (11% +/- 5%) or multipotent (5% +/- 4%) progenitor cells. Selective inhibition by patient AP serum of CFU-GM (74% +/- 11%) was also seen against two allogeneic marrows. Patient CP serum no longer inhibited (6% +/- 4%) autologous CFU-GM. Addition of Chl (5 to 120 micrograms/mL) to CP serum but not to control serum resulted in potent drug concentration-dependent complement-mediated inhibition of autologous and allogeneic CFU-GM. Inhibition of CFU-GM in the presence of Chl was no longer demonstrable following immunoabsorbent removal of IgG from patient serum. Patient serum in the presence of Chl had limited activity against morphologically recognizable marrow granulocytic precursors in a microimmunofluorescence assay. These results are most consistent with the development of Chl-dependent, selective antibody-mediated immune inhibition of granulopoiesis.

Immunophenotypic transformation from acute undifferentiated leukemia to Burkitt's-like acute lymphoblastic leukemia

Progression of more differentiated to less differentiated malignant phenotypes has been described infrequently during the natural evolution or at relapse of treated hematopoietic malignancies. This report describes an unusual instance of immunophenotypic transformation from an immunologically undifferentiated acute leukemia to a leukemia that at relapse possessed morphologic and immunologic markers characteristic of a Burkitt's-like acute lymphoblastic leukemia. A 26-year-old man initially presented with pancytopenia and a bone marrow diffusely replaced with blast cells morphologically most consistent with a French-American-British L2 subclassification. The surface immunophenotype of the blasts at diagnosis showed HLA-DR surface antigen but no myeloid, lymphoid, or immunoglobulin determinants. Despite successful induction and ongoing consolidation chemotherapy, the patient had a relapse five months after diagnosis; blast cells at relapse demonstrated marked cytoplasmic vacuolation consistent with a Burkitt's-like L3 acute lymphoblastic transformation. Immunophenotypic analysis revealed the presence of restricted immunoglobulin determinants (mu heavy chain and kappa light chain), as well as two separate B lineage surface determinants (BA-1 and B-1). Immunophenotypic transformations may reflect the presence of either a multiclonal or multipotent leukemic population; documentation of the frequency of such transformations and genomic analysis of the transformed subpopulations may be helpful in furthering the understanding of molecular mechanisms involved in leukemogenesis.

Decreased methylation rates of DNA in SV40-transformed human fibroblasts

The rates of methylation of total cellular DNA and newly synthesized DNA were measured in four unrelated SV40-transformed human fibroblast lines and in four control parent fibroblast lines. Rates of methylation of total cellular DNA were decreased by a factor of 1.8-2.3 in the transformed cells relative to control cells. Methylation was largely (75%-87%) restricted to newly synthesized DNA in control and transformed fibroblasts, and methylation rates of newly synthesized DNA were diminished in transformed cells by 12- to 19-fold relative to control cells. Growth rates were similar in the normal and transformed cells. The cellular uptake of methionine and conversion to S-adenosylmethionine were similar in the normal and transformed cells, suggesting no major differences between the normal and transformed cells in the cellular transport of methionine, methionine S-adenosyltransferase activity, or the intracellular concentrations of methionine and S-adenosylmethionine. The diminished rates of DNA methylation that we have observed suggest a possible mechanism for altered gene expression and growth control in transformed cells.

Cellular immunoabsorption using monoclonal antibodies. Selective removal of T cells from peripheral blood and bone marrow

T cells can be selectively removed from human peripheral blood and bone marrow by passage over a column containing monoclonal anti-T-cell antibodies covalently attached to Sepharose 6MB gel. Effective depletion of T cells from peripheral blood mononuclear cells (PBMC) resulted in the appearance of Leu-2-positive cells, most of which do not express Leu-1 or Leu-4 antigens. Using a column containing anti-Leu-1 or anti-Leu-4 attached to Sepharose 6MB gel, depletion of 98.3% and 99% of T cells from bone marrow mononuclear cells (BMMC), respectively, was demonstrated with recovery of approximately 75% of non-T cells. These columns removed 92.3-98.4% T cells from PBMC with 43.5-74.8% recovery of non-T cells. Combining anti-Leu-1 and anti-Leu-4 antibodies on the same gel removed all detectable T cells from PBMC and BMMC. Proliferative responses to the T cell mitogen, phytohemagglutinin, were abolished from both PBMC and BMMC after column treatment. Preservation of hematopoietic progenitors was observed after treatment of bone marrow, with stem cell recovery averaging 83 +/- 26% for burst-forming units (erythroid), 86 +/- 14% for granulocyte-macrophage progenitors and 94 +/- 16% for granulocyte, erythroid macrophage, and megakaryocitic elements. These results suggest that clinical application of cellular immunoabsorption techniques using monoclonal antibodies will be useful in bone marrow transplantation.

Primary non-Hodgkin's lymphoma of the mediastinum

Non-Hodgkin's lymphoma localized to the mediastinum and adjacent structures occurred in 12 of 215 (6+) non-Hodgkin's lymphoma patients seen at the Massachusetts General Hospital between 1975 and 1979. Lymphangiography, radionuclide scanning and whole body computerized tomography were used to exclude patients with extrathoracic disease at presentation. Eleven of the 12 patients presented with extensive contiguous extranodal disease (Stage IIE) with involvement of either the pericardium, sternum, chest wall, pulmonary parenchyma or, in four cases, with superior venacaval obstruction. Diffuse large cell lymphoma (eight cases) and diffuse poorly differentiated lymphocytic lymphoma (four cases) were the prevalent histologic subtypes; no instances of lymphoblastic lymphoma without extrathoracic spread were encountered. None of four lymphomas studied could be characterized as either B- or T-cell tumors utilizing conventional surface marker techniques. Ten of the 12 patients achieved complete remissions, either after treatment with combination chemotherapy alone (three patients) or after both chemotherapy and mediastinal irradiation (seven patients). Two of these ten have subsequently relapsed, but median survival has not been reached after a mean period of observation of 28 months. Primary nonlymphoblastic non-Hodgkin's lymphoma of the mediastinum is more common than previously realized, displays aggressive contiguous spread within the chest and responds well to combination chemotherapy with or without adjuvant mediastinal irradiation.

Further studies on the mechanism of marrow granulocytic hyperplasia in mice chronically injected with endotoxin

Marrow granulocytic hyperplasia occurs regularly in mice injected with endotoxin for 7--30 d, despite minimal elevations of serum colony-stimulating activity (CSA). Alterations in marrow granulocyte-monocyte progenitor (CFU-C) number of changes in marrow cell cycle status do not explain this hyperplasia. We have studied other mechanisms which may explain this increased granulopoiesis. CF1, BDF1 or C57bl/6J mice were infected with 10 micrograms of S. typhosa endotoxin i.p. daily for 7--20 d. Control and endotoxin injected (tolerant) sera, each with identical levels of CSA, were assayed against control marrow cells stimulated with supramaximal amounts to CSA to assess the role of serum potentiators in augmenting granulopoiesis. In six separate experiments, tolerant sera, over a 30-fold concentration range, produced a 1.7--4.0-fold potentiation of colony growth compared to control sera (P less than 0.001). No increased tolerant sera potentiation was seen over a similar concentration range when assayed against tolerant marrow. Tolerant and control splenic conditioned media, both dialysed and non-dialysed, failed to potentiate control marrow colony growth. Tolerant marrow stem cells did not show changes in CSA sensitivity, colony size distribution or differentiation, and tolerant bone or bone marrow cells did not produce increased amounts of CSA. We conclude that serum factors separate from CSA may in part explain the increased granulopoiesis seen in endotoxin injected mice. The failure of tolerant sera to potentiate tolerant marrow growth in vitro may reflect prior in vivo exposure of marrow to these potentiating factor(s).

The effect of lithium on murine hematopoiesis in a liquid culture system

Lithium carbonate has been shown to increase granulocyte production. We studied the effect of lithium on murine hematopoiesis in a liquid culture system providing for the prolonged growth of stem cells and their progeny. After one week of incubation, lithium, at a supernatant concentration of 1 mmol per liter, increased murine pluripotent stem cells (CFU-S, or colony-forming units in spleen) to 232 per cent of control values (P less than 0.001), granulocyte-monocyte progenitor cells (CFU-C, or colony-forming units in culture) to 218 per cent of control values (P less than 0.0001), granulocytes to 125 per cent of control values (P less than 0.01), and megakaryocytes to 246 per cent of control values (P less than 0.001). These increases were associated with transient elevations in colony-stimulatory activity. Prolonged exposure to lithium (three to 12 weeks) was associated with a dose-dependent progressive depletion of stem cells and their progeny. Lithium enhancement of granulopoiesis may be explained by primary stimulation of the pluripotent stem cell. Prolonged proliferative stress induced by lithium when the stem-cell reserve is limited may be associated with diminished replicative potential of the stem cells and rapid depletion of cells.

CNS involvement in the non-Hodgkin's lymphomas

Instances of central nervous system (CNS) lymphomatous involvement occurring amongst 592 cases of non-Hodgkin's lymphoma (NHL) seen between 1967 and 1977 were reviewed. Lymphomatous complications of the CNS were found in 52 patients (9%): 24 with meningeal lymphoma, 20 with epidural compression and 8 with intracerebral lymphoma. Intracerebral lymphoma presented clinically as large parenchymal deposits of tumor unrelated to leptomeningeal disease. Ninety-eight percent (50/52) of all patients had a diffuse histologic subtype and 82% (42/52) had either histiocytic or diffuse, poorly differentiated lymphocytic lymphoma. Bone marrow involvement was an additional determinant of risk and aided in the selection of patients for possible CNS prophylaxis. Either meningeal or intracerebral lymphoma developed in 35% (6/17) of patients with diffuse histiocytic lymphoma and positive bone marrow biopsies. This subgroup was particularly felt to warrant CNS prophylaxis. Further diagnostic and therapeutic management regarding CNS involvement in NHL is discussed.

Mortality in gold and coal miners in Western Australia with special reference to lung cancer

Cohorts of 1974 gold miners and 213 coal miners in Western Australia surveyed for respiratory symptoms, smoking habits, occupational history and radiographic evidence of pneumoconiosis have been followed up for 13-14 years. Overall, neither group had a significantly higher mortality than expected from the experience of Western Australian men in general. Lung cancer mortality was relatively high in the gold miners (59 deaths observed, 40.8 expected) but weakly and inconclusively related to the extent of their underground mining experience. Cigarette smoking may explain the excess of lung cancer in the gold miners because the prevalence of the habit in the latter (66.3%) was higher than in the coal miners (58.7%) or in other men in Western Australia (53.2%). Radiographic evidence of silicosis was present in 21.7% of the gold miners but did not appear to have contributed substantially to their mortality. The coal miners showed a lower than expected rate of lung cancer but an excess of deaths from all other forms of cancer (11 observed, 5.6 expected). This excess was not attributable to any one cancer site and cannot be explained readily.