Serum chemokine levels in patients with non-progressing HIV infection

OBJECTIVE

To evaluate serum chemokines, macrophage inflammatory protein (MIP)-1 alpha, MIP-1 beta and RANTES, concentrations in non-progressing HIV-infected patients and AIDS patients.

SETTING

University Hospital-based AIDS Clinical Trials Unit.

DESIGN/METHODS

Serum MIP-1 alpha, MIP-1 beta and RANTES levels were determined by enzyme-linked immunosorbent assay using archived serum specimens obtained on two occasions at least 1.8 years apart.

PATIENT SELECTION

Long-term non-progressing HIV-infected adult patients were identified from clinic records. For each non-progressing patient two adult AIDS patients with initial documentation of seropositivity the same year and the same length of follow-up were selected.

RESULTS

Four long-term non-progressing patients and eight AIDS patients were studied. Neither the duration of known HIV positivity at the time of specimen collection nor the length of time between specimen collections differed significantly between non-progressing patients and AIDS patients. Serum levels of MIP-1 alpha, MIP-1 beta and RANTES in specimens obtained either early or later in the course of HIV infection did not differ significantly between non-progressing patients and AIDS patients. In the two patient subsets, significant differences in serum chemokine levels over time were not observed. The rate of change of serum chemokine concentration over time also did not differ between non-progressing patients and AIDS patients. Serum MIP-1 alpha and MIP-1 beta levels did not reach levels reported to suppress HIV proliferation in vitro. When expressed as a quantity per peripheral blood CD8+ lymphocyte, AIDS patients exhibited significantly greater levels of MIP-1 alpha, MIP-1 beta and RANTES than non-progressing HIV patients (P < 0.05). These values did not exhibit a significant variation over time.

CONCLUSIONS

Serum MIP-1 alpha, MIP-1 beta and RANTES levels do not distinguish patients with AIDS from patients with non-progressing HIV infection. Variations in levels of these chemokines do not explain individual variation in the natural history of HIV infection.

Expression of receptor protein tyrosine kinase tif is regulated during leukemia cell differentiation

tif is a recently cloned and characterized cDNA predicting a transmembrane protein with a putative tyrosine kinase structure in its cytoplasmic domain. By analysis of the purified tif cytoplasmic domain expressed in Escherichia coli, we have demonstrated that tif is an active protein tyrosine kinase capable of autophosphorylation on tyrosine residues and this phosphorylation is inhibited by a tyrosine-specific inhibitor genistein. Northern blot analyses of various leukemia cell lines have revealed that tif mRNA expression is primarily confined to those bearing erythroid and megakaryocytic phenotypes. Megakaryocytic differentiation of K562 and HEL cells induced by phorbol 12-myristate 13-acetate is accompanied by down-regulation of tif mRNA expression. In addition, treatment of K562 and HEL with hexamethylene bis-acetamide, but not with hemin, decreases the steady-state level of tif mRNA. These combined results suggest that the receptor tyrosine kinase tif is involved in hematopoietic development.

Erythropoietin and cytokine levels in the anemia of severe alcoholic liver disease

PURPOSE

The anemia of chronic disease is mediated by the cytokines that modulate the immune response, such as tumor necrosis factor (TNF) and gamma-interferon (gamma-IFN), and is associated with a blunted serum erythropoietin (sEPO) response to anemia. Previous reports suggest that patients with liver disease (LD) also exhibit a blunted sEPO response to anemia, and that patients with alcoholic LD had altered cytokines, including elevated TNF levels. To investigate the pathogenesis of anemia in alcoholic LD, sEPO, TNF, and gamma-IFN levels were determined in patients who had participated in a Department of Veterans Affairs Cooperative study of alcoholic LD.

METHODS

sEPO, serum TNF-alpha, and serum gamma-IFN levels were evaluated in 40 patients with severe biopsy-proven alcoholic LD whose serum had been stored during the Department of Veterans Affairs Cooperative Study 275, and in 18 patients with iron deficiency (controls).

RESULTS

Mean hemoglobin (Hgb) was 11.2 +/- 0.3 g/dl for LD patients versus 11.4 +/- 0.4 g/dl for controls (p = 0.84). sEPO levels measured by ELISA were 29.6 +/- 4.1 units/liter in LD patients versus 25.4 +/- 5.4 units/liter in controls (p = 0.64). In both sets of patients, sEPO and Hgb were inversely related; the slopes of the two regression lines did not differ significantly (p = 0.92). TNF was detected in 3 of 40 LD patients and in 0 of 18 iron-deficient patients. Detection of TNF did not correlate with sEPO or Hgb, but did correlate strongly with severe caloric malnutrition (marasmus) and mortality at 6 months (p = 0.049 and 0.04, respectively). gamma-IFN was not detected.

CONCLUSIONS

These findings indicate that the sEPO response is preserved in patients with severe alcoholic LD, and suggest that anemia in LD arises from different mechanisms than does the anemia of chronic disease. TNF production in severe alcoholic LD is strongly correlated with caloric malnutrition and mortality.

Inhibition of human erythroid colony-forming units by interferons alpha and beta: differing mechanisms despite shared receptor

Previous investigations have demonstrated that interferons alpha, beta, and gamma (alpha-, beta-, and gamma-IFN) are potent inhibitors of erythropoiesis in vitro. By utilizing a cell population enriched for human erythroid colony-forming units (CFU-E), we have previously demonstrated that the inhibitory effects of beta- and gamma-IFNs are direct effects, not requiring the presence of accessory cells, and that the inhibitory effect of recombinant human (rh) gamma-IFN could be corrected by high concentrations of rh erythropoietin (Epo). In this study, we compared the effects of rh(alpha)-IFN on cells enriched for CFU-E to its effects on unpurified marrow cells and found that although h(beta)-IFN (which shares a common receptor with alpha-IFN) directly inhibits CFU-E colony formation, the effect of rh(alpha)-IFN is indirect and is mediated by a soluble factor released from T lymphocytes in response to rh(alpha)-IFN. However, rh(alpha)-IFN enhanced the direct inhibitory effect of rh(gamma)-IFN on CFU-E not inhibited by rh(alpha)-IFN. The inhibitory effects of neither alpha- nor beta-IFN could be overcome by high levels of rhEpo. These findings imply that alpha- and beta-IFN exert different cellular effects despite binding to the same receptor. Failure of rhEpo to correct CFU-E colony inhibition by alpha- and beta-IFNs but not by gamma-IFN also suggests a mechanism for the differing degrees of response to different doses of rhEpo in patients with the anemia of chronic disease.

Extremely elevated serum ferritin levels in a university hospital: associated diseases and clinical significance

PURPOSE

To establish the frequency with which serum ferritin levels > or = 1,000 ng/mL occur in a general hospital population, and to determine the clinical significance of this finding.

PATIENTS AND METHODS

All serum ferritin determinations performed between June 1992 and July 1993 at the University of Cincinnati Medical Center were reviewed and patients with serum ferritin levels > or = 1,000 ng/mL identified. The medical records of these patients were then reviewed.

RESULTS

Of 1,826 serum ferritin determinations performed during the study period, 122 (6.7%) were > or = 1,000 ng/mL. Associated clinical syndromes found in the 95 patients with serum ferritin > or = 1,000 ng/mL included liver disease (20.0%), renal disease (17.9%), malignant disease (17.9%), human immunodeficiency virus (HIV) infection (16.8%), non-HIV systemic infections (15.8%), chronic transfusions (10.5%), and sickle cell syndromes (10.5%). No syndrome usually associated with extreme serum ferritin elevations was identified in 8.4% of patients, and 16.8% of the patients fell into more than one category. The highest mean serum ferritin levels occurred in the chronically transfused and sickle cell groups. Concomitant serum transferrin saturation values were determined with 82 (86.3%) of the elevated serum ferritin levels and did not correlate well with them. The highest mean transferrin saturation levels occurred in the liver disease group. Transferrin saturation > or = 50%, suggestive of iron overload, was significantly more frequent in the liver disease group (P = 0.002); and saturation < or = 15%, suggestive of iron-deficient erythropoiesis, was significantly more frequent in the HIV group (P = 0.001).

CONCLUSION

Outside the setting of clinical syndromes associated with iron overload (liver disease, transfusions, sickle cell syndromes), serum ferritin levels > or = 1,000 ng/mL serve as a nonspecific marker for a variety of significant disorders, including infectious and neoplastic diseases. Further study of the regulation of ferritin production may provide insight into the pathogenesis of disorders associated with extreme serum ferritin elevations.

Erythropoietin in the treatment of anemia in chronic infectious, inflammatory, and malignant diseases

The anemia associated with chronic infectious, inflammatory, and malignant diseases is characterized by a blunted erythropoietin response; for any given decrease in hemoglobin or hematocrit, the increase in serum or plasma erythropoietin is less than would be found in an equally anemic patient with iron deficiency. This observation provides a rationale for the use of recombinant human erythropoietin in the treatment of the anemia in these diseases. During the past year, new information has been reported on the pathophysiology of erythropoiesis in chronic infectious, inflammatory, and neoplastic diseases, and on the use of recombinant human erythropoietin for this anemia. This article reviews these developments.

Pathogenesis of the anemia of chronic disease: a cytokine-mediated anemia

The anemia found in patients with chronic infectious, inflammatory and neoplastic disorders, known as the anemia of chronic disease (ACD), is one of the most common syndromes in medicine. A characteristic finding of the disorders associated with ACD is increased production of the cytokines which mediate the immune or inflammatory response, such as tumor necrosis factor, interleukin 1 and the interferons. All the processes involved in the development of ACD can be attributed to these cytokines, including shortened red cell survival, blunted erythropoietin response to anemia, impaired erythroid colony formation in response to erythropoietin and abnormal mobilization of reticuloendothelial iron stores. Improved understanding of the role played by cytokines in the pathogenesis of ACD may lead to the development of more specific therapy for this syndrome.

Treatment of aplastic anemia with an investigational antilymphocyte serum prepared in rabbits

The authors evaluated antilymphocyte serum prepared in rabbits (ALS-R) as an alternative to antilymphocyte serum prepared in horses (ALG-H) in the therapy of aplastic anemia. Between 1980 and 1993, 57 evaluable patients received ALS-R and prednisone +/- cyclosporine +/- androgens. Standard response criteria were used and patients were evaluated at 3 months from the start of therapy. Median age was 43 years. Disease was present for up to 2 months in 24 patients, 2-5 months in 14 patients, and 6 months or more in 19 patients. Disease was severe in 30 patients and moderate in 27. Responses occurred in 16 (28%) of 57 patients. Responses were more frequent in females, in patients treated within 6 months of diagnosis, and in patients with severe disease. Among patients receiving ALS-R and cyclosporine within 2 months of diagnosis, 46% responded. After ALS-R therapy, 20 patients received ALG-H; 8 (40%) of 20 responded. Eight patients receiving ALS-R previously had received ALG-H; 2 (25%) of these 8 patients responded. Toxicity of ALS-R was minimal. Antilymphocyte serum prepared in rabbits, in conjunction with other immunosuppressive agents, represents an effective alternative to ALG-H in aplastic anemia, especially in patients previously treated with ALG-H.

Clinical application of recombinant erythropoietin in the anemia of chronic disease

The anemia of chronic disease is a consequence of the abnormal production of cytokines associated with chronic inflammatory, infectious, and neoplastic disorders. rhEPO can correct the impaired erythropoiesis encountered with this syndrome in vitro and in the clinical setting. Although most patients with the anemia of chronic disease will not require specific intervention to increase their hemoglobin and hematocrit, certain subsets of patients may benefit from rhEPO therapy. These include patients with anemia sufficiently severe to require transfusion, and patients for whom autologous blood donation is precluded by anemia.

Inhibition of murine erythroid colony formation in vitro by interferon gamma and correction by interferon receptor immunoadhesin

It has been previously reported that inhibition of human erythroid colony-forming units (CFU-E) in vitro by interleukin-1 (IL-1) is an indirect effect, occurring through the production of interferon gamma (IFN gamma). IFN gamma, in turn, inhibits CFU-E colony formation directly, and its inhibitory effect can be overcome by exposure to high concentrations of erythropoietin (EPO). To develop an in vitro animal model for investigating inhibition of erythropoiesis by IFN gamma, the effects of recombinant murine (rm) IFN gamma on highly purified CFU-E from the spleens of mice infected with the anemia strain of the Friend virus (FVA) were studied. rmIFN gamma inhibited CFU-E colony formation in a dose-dependent manner. This inhibition occurred with large (> or = 8 cell) colonies only; smaller colonies were not affected. The inhibitory effect was corrected to 72% of control by high EPO concentrations of 64 U/mL. Murine CFU-E were then cultured with rmIFN gamma in the presence of a soluble murine IFN gamma receptor fused to the hinge and Fc domains of the human IgG1 heavy chain (mIFN gamma R-IgG). Inhibition of CFU-E colony formation by rmIFN gamma (100 U/mL) was corrected by mIFN gamma R-IgG in a dose-dependent manner, with an approximate IC50 of 0.05 nmol/L, and complete or near complete correction at 0.5 nmol/L. Similarly, a human IFN gamma R-IgG greatly reduced the inhibitory effect of recombinant human IFN gamma on human CFU-E. These experiments provide an in vitro animal model for studying the inhibitory effects of IFN gamma on erythropoiesis and indicate that IFN gamma R-IgG may be a useful agent for reducing the toxicity of IFN gamma in vivo.

Inhibition of human erythroid colony-forming units by tumor necrosis factor requires beta interferon

We have previously reported that inhibition of human CFU-erythroid (E) colony formation by tumor necrosis factor (TNF) is an indirect effect mediated by a soluble factor released from a fraction of marrow accessory cells which are predominantly stromal elements (Means, R. T., Jr., E. N. Dessypris, and S. B. Krantz. 1990. J. Clin. Invest. 86:538-541). Further studies reported here identify a mediator of this effect. The inhibitory effect of recombinant TNF on marrow CFU-E is ablated by neutralizing antibodies to human beta IFN, but not by antibodies to gamma IFN or IL-1. Anti-beta IFN also neutralizes the inhibitory effect of conditioned medium prepared from marrow cells exposed to TNF. Human beta IFN inhibits colony formation by unpurified marrow CFU-E as well as highly purified CFU-E generated from peripheral blood progenitors, and limiting dilution analysis shows that this is a direct inhibitory effect. TNF has been implicated in the pathogenesis of the anemia of chronic diseases since blood TNF levels are elevated in many patients with this syndrome, and since exposure to TNF produces a similar anemia in either humans or mice. The present study demonstrates that beta IFN is a required mediator of this inhibitory effect on erythropoiesis.

Progress in understanding the pathogenesis of the anemia of chronic disease

Improved understanding of the inflammatory response and the identification and characterization of the specific cytokines involved, as well as improved understanding of erythropoiesis, and the availability of recombinant human growth factors such as EPO, have greatly enhanced our appreciation of the pathogenesis of ACD by allowing development of a number of informative models for studying this syndrome. It appears that a variety of cytokines are involved in all aspects of the pathogenesis of ACD, from the inhibition of erythroid progenitors and EPO production to impairment of iron release. A schematic of the contributions of some of these cytokines to the development of ACD is shown in Fig 6. The exact biochemical mechanisms by which these effects occur is still to be determined. The progress outlined in this report has allowed us to develop a more precise understanding of the pathogenesis of this common and important clinical syndrome. In 1983, Hansen subtitled a review of ACD "A Bag of Unsolved Questions." Although this description is still accurate, our understanding of ACD has now developed to the point where we can offer a more defined subtitle: "A Bag of Cytokines."

Polycythemia vera. II. Hypersensitivity of bone marrow erythroid, granulocyte-macrophage, and megakaryocyte progenitor cells to interleukin-3 and granulocyte-macrophage colony-stimulating factor

Polycythemia vera (PV) is a clonal disease of the hematopoietic stem cell characterized by a hyperplasia of marrow erythropoiesis, granulocytopoiesis, and megakaryocytopoiesis. We previously reported that highly purified PV blood burst-forming units-erythroid (BFU-E) are hypersensitive to recombinant human interleukin-3 (rIL-3). Because these cells may be only a subset, and not representative of marrow progenitors, we have now studied partially purified marrow hematopoietic progenitor cells. Dose-response experiments with PV marrow BFU-E showed a 38-fold increase in sensitivity to rIL-3 and a 4.3-fold increase in sensitivity to recombinant human erythropoietin (rEpo) compared with normal marrow BFU-E. In addition, PV marrow colony-forming units-granulocyte-macrophage (CFU-GM) and CFU-megakaryocyte (CFU-MK) also showed a marked hypersensitivity to rIL-3 and to human recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF). Dose-response curves with rGM-CSF and blood BFU-E showed a 48-fold increase in sensitivity. No effect of rIL-4, rIL-6, human recombinant granulocyte-CSF (rG-CSF), or macrophage-CSF (rM-CSF) was evident, nor was there any effect of PV cell-conditioned medium on normal BFU-E, when compared with normal cell-conditioned medium. Autoradiography with 125I-rEpo showed an increase in Epo receptors after maturation of PV BFU-E to CFU-E similar to that shown with normal BFU-E, but no increase of specific binding of 125I-rIL-3 by PV CD34+ cells was seen compared with normal CD34+ cells. These studies show that PV marrow hematopoietic progenitor cells are hypersensitive to rIL-3 and rGM-CSF, similar to PV blood BFU-E. While the mechanism does not appear to be due to enhanced binding of rIL-3, the hypersensitivity of PV progenitor cells to IL-3 and GM-CSF may be a key factor in the pathogenesis of PV.

Inhibition of human erythroid colony-forming units by interleukin-1 is mediated by gamma interferon

IL-1 inhibits erythropoiesis in vivo and in vitro. This inhibition was studied by comparing the effect of recombinant human IL-1 (rhIL-1) on highly purified CFU-erythroid (E) generated from peripheral blood burst-forming units-erythroid (BFU-E) (mean purity 44.4%) with its effect on unpurified marrow CFU-E (mean purity 0.36%). Colony formation by marrow CFU-E was significantly inhibited by rhIL-1, while colony formation by highly purified CFU-E was not inhibited. However, purified CFU-E colonies were inhibited by rhIL-1 in the presence of autologous T-lymphocytes, and also by cell-free conditioned medium prepared from T-lymphocytes stimulated by rhIL-1. This inhibitory effect was ablated by neutralizing antibodies to gamma interferon (IFN), but not by antibodies to human IL-1, tumor necrosis factor, or beta IFN. Colony formation by highly purified CFU-E was also inhibited by recombinant human gamma IFN (rh gamma IFN). IL-1 and gamma IFN play significant roles in the pathogenesis of the anemia of chronic disease. These studies indicate that rhIL-1 inhibits CFU-E colony formation by an indirect mechanism involving T-lymphocytes and requiring gamma IFN and that gamma IFN itself is most probably the direct mediator of this effect.

Inhibition of human erythroid colony-forming units by gamma interferon can be corrected by recombinant human erythropoietin

Tumor necrosis factor (TNF), interleukin-1 (IL-1), and gamma interferon (gamma IFN) inhibit erythropoiesis in vivo and in vitro, and have been implicated in the pathogenesis of the anemia of chronic disease. Anemia in patients with rheumatoid arthritis and in animals exposed chronically to IL-1 and TNF can be corrected by the administration of recombinant erythropoietin (Epo). We exposed highly purified human erythroid colony-forming units (CFU-E) cultured from peripheral blood burst-forming units-erythroid (BFU-E) and unpurified human marrow CFU-E to recombinant human gamma IFN and showed inhibition of colony formation in vitro. This inhibition was reversed by increased concentrations of Epo. The mechanisms by which this effect occurs are unknown at present. Epo may cause a downregulation of gamma IFN receptor expression on CFU-E or, alternatively, gamma IFN may cause a downregulation of Epo receptor expression. A full understanding of these mechanisms awaits a more complete comprehension of the regulation of erythropoiesis; however, the effect of Epo in vitro is similar to its ability to correct the anemia of chronic disease in vivo.

Quantitation of insulin-like growth factor-I binding to highly purified human erythroid colony-forming units

A method has been developed by which erythroid colony-forming units (CFU-E) may be obtained from human blood in sufficient number and purity for quantitative studies of growth factor binding. Studies in serum-free medium have shown that CFU-E require the addition of only two growth factors, erythropoietin (EP) and insulin-like growth factor-I (IGF-I), for growth and differentiation. The IGF-I may be replaced by higher (100-fold) concentrations of insulin. Incubation of CFU-E with 125I recombinant human IGF-I (rhIGF-I) at 4 degrees C has demonstrated specific binding that is directly proportional to the cell concentration. Competition with unlabeled rhIGF-I markedly decreased binding, whereas other growth factors such as granulocyte-monocyte colony-stimulating factor (GM-CSF), interleukin 3 (IL-3), and epidermal growth factor (EGF) had no significant effect on the binding of [125I]rhIGF-I. The binding was saturable at an [125I]rhIGF-I concentration of 10 ng/ml (1.2 nM). Scatchard analysis revealed two classes of IGF-I receptors present on the CFU-E cell surface: a low-affinity class of 549 receptors with Kd = 0.44 nM and a high-affinity class of 341 receptors with Kd = 0.04 nM.

Treatment of refractory pure red cell aplasia with cyclosporine A: disappearance of IgG inhibitor associated with clinical response

Remissions were obtained in 6/9 evaluable patients with pure red cell asplasia (PRCA) refractory to other immunosuppressive agents who were treated with cyclosporine A (CsA). Four of these patients have remained in continuous remission off all treatment for 4-19 months. Another patient who stopped CsA abruptly relapsed, but responded to reinstitution of therapy. The sixth patient died of a cerebrovascular accident while in remission on a low dose of CsA. Acute side effects were minimal and were responsive to dose reduction. One patient developed a lymphoma while in an unmaintained remission, and one patient who did not respond to CsA was found to have a lymphoma approximately a year after stopping treatment. In vitro studies of autologous erythroid progenitors in a patient with an IgG inhibitor of erythropoiesis showed a reduction of autoantibody associated with the response to CsA. The antigen to which this inhibitor is directed was expressed only during the marrow erythroid burst-forming unit (BFU-E) period of erythroid differentiation. CsA can induce sustained remissions in cases of PRCA refractory to other multiple agents, and these remissions may be associated with a reduction in autoantibody to erythroid progenitor cells. Further studies of patients with PRCA who respond to CsA may lead to an improved understanding of this disorder.

Polycythemia vera blood burst-forming units-erythroid are hypersensitive to interleukin-3

Because polycythemia vera (PV) is a clonal hematopoietic stem cell disease with a trilineage hyperplasia, and interleukin-3 (IL-3) stimulates trilineage hematopoiesis, we have studied the response of highly purified PV blood burst-forming units-erythroid (BFU-E) to recombinant human IL-3 (rIL-3). Whereas the growth of normal blood BFU-E in vitro rapidly declined by 40 and 60% after 24 and 48 h of incubation without 50 U/ml of rIL-3, the growth of PV BFU-E declined by only 10 and 30% under the same conditions, demonstrating a reduced dependence on rIL-3. A reduced dependence of PV BFU-E on recombinant human erythropoietin (rEP) was also present. Dose-response experiments showed a 117-fold increase in PV BFU-E sensitivity to rIL-3, and a 6.5-fold increase in sensitivity to rEP, compared to normal BFU-E, whereas blood BFU-E from patients with secondary polycythemia responded like normal BFU-E. Endogenous erythroid colony (EEC) formation, which is independent of the addition of rEP, was reduced by 50% after erythroid colony-forming cells were generated from PV BFU-E in vitro without rIL-3 for 3 d, whereas rEP-stimulated erythroid colonies were unaffected. These studies demonstrate a striking hypersensitivity of PV blood BFU-E to rIL-3, which may be the major factor in the pathogenesis of increased erythropoiesis without increased EP concentrations.

Inhibition of human colony-forming-unit erythroid by tumor necrosis factor requires accessory cells

Recombinant tumor necrosis factor (rTNF) inhibits erythropoiesis in vivo and in vitro. To study the mechanism of this inhibition, the effect of rTNF on highly purified human CFU-erythroid (E) (mean purity 63.5%), which were generated from peripheral blood burst-forming units-erythroid (BFU-E), was compared to its effect on unpurified human marrow CFU-E (mean purity 0.21%). Although growth of colonies from marrow CFU-E was inhibited by rTNF, no significant effect on purified BFU-E-derived CFU-E colony growth was found. Removal of accessory marrow cells by soy bean agglutinin (SBA) ablated the inhibition of marrow CFU-E colonies by rTNF. Inhibition of colony growth was then restored by adding back SBA+ cells, but not by adding T lymphocytes or adherent cells. Conditioned medium prepared from bone marrow mononuclear cells stimulated by rTNF inhibited the growth of colonies from highly purified BFU-E derived CFU-E resistant to direct inhibition by rTNF. These findings indicate that rTNF does not directly inhibit CFU-E, but requires accessory cells to decrease erythropoiesis. These accessory cells reside in the SBA+ cell fraction, but are neither T cells nor adherent cells. Therefore, in order to produce anemia, TNF must induce release or production of a factor that directly inhibits erythroid colony growth.

Erythropoietin receptors in polycythemia vera

The role of erythropoietin (EP) in polycythemia vera (PV) is controversial, with some experiments suggesting that erythroid progenitors in PV are exquisitely sensitive to EP and EP dependent, and others suggesting that PV progenitors are EP independent. We have examined the characteristics of the EP receptor (EP-R) on erythroid colony-forming cells (ECFC) from patients with PV. In contrast to normal ECFC, which have two classes of EP-R, with 20% showing high affinity (Kd = 0.13 nM; range, 0.04-0.20 nM) and the remainder lower affinity (Kd = 0.37 nM; range, 0.28-0.57 nM), PV ECFC show a single class of 851 low affinity EP-R with Kd = 0.72 nM (range, 0.36-0.85 nM). ECFC from patients with secondary (EP driven) polycythemia or anemia show two classes of EP-R (Kd = 0.18 and 1.10 nM, respectively). Attempts to remove tightly bound EP from putative high affinity EP-R in PV did not reveal any higher affinity receptors. Determination of molecular size by crosslinking showed two proteins of 90 and 100 kD similar to those seen with normal EP-R. These studies indicate the PV ECFC have EP-R that are structurally similar to normal EP-R but lack the higher binding affinity for EP.

Treatment of the anemia of rheumatoid arthritis with recombinant human erythropoietin: clinical and in vitro studies

Two anemic patients with rheumatoid arthritis were treated with recombinant human erythropoietin (EPO) for 5 months. Both patients showed significant increases in hematocrit, red cell volumes, and marrow erythroid and megakaryocyte progenitor cells. No significant toxic effects from EPO were observed. These data indicate that EPO may be effective in overcoming the pathogenetic factors that limit erythropoiesis in rheumatoid arthritis.

Plasmacytic neoplasm of the gastrointestinal tract in a patient with long-standing monoclonal gammopathy

We have reported the 21-year follow-up of a patient with progressive monoclonal IgG lambda gammopathy and recurrent pneumococcal infections who had diarrhea and weight loss. The serum IgG had risen from 2,850 mg/dl in 1966 to 6,120 mg/dl in 1986, but repeated evaluations had shown no evidence of myeloma or lymphoma. Evaluation revealed infiltration of the gastrointestinal tract by a plasmacytic malignancy with a surface heavy and light chain identical to her serum monoclonal band.

Re-treatment of aplastic anemia with antithymocyte globulin or antilymphocyte serum

Twenty-two patients with aplastic anemia were treated with antilymphocyte serum or antithymocyte globulin at Vanderbilt University and affiliated hospitals from 1980 to 1986. The median age was 42 (eight to 73 years); the male:female ratio was 8:14. Nineteen patients had severe aplastic anemia, and three had moderate disease. Twenty patients received antilymphocyte serum initially while two patients received antithymocyte globulin. Fifteen patients received fluoxymesterone 10 mg by mouth three times a day with antilymphocyte serum, and all received prednisone during the course of antilymphocyte serum or antithymocyte globulin. There were seven responses (31.8 percent) to the first course with four complete responses and three partial responses. Six of 15 patients who received fluoxymesterone showed a response, compared with zero of five treated without androgens (p less than 0.05). Eight patients with no initial response and a patient who experienced a relapse after a complete response were re-treated with either antithymocyte globulin (six) or antilymphocyte serum (three), with four of nine patients (44 percent) having a response (three complete responses, one partial response). Overall, 10 of 22 patients (45 percent) had a response (six complete responses, four partial responses). Median survival for those without a response is six months. Median survival for those with a response has not been reached, with follow-up ranging from 18 to 70 months. This study shows the benefit of a second cycle of antilymphocyte serum or antithymocyte globulin and a possible role for concomitant androgens in this treatment of aplastic anemia.