The significance of HLA-DRB1 matching on clinical outcome after HLA-A, B, DR identical unrelated donor marrow transplantation

Despite matching for serologically defined HLA-A, B, DR antigens, acute graft-versus-host disease (GVHD) is a major complication contributing to increased morbidity and mortality in patients who undergo marrow transplantation from unrelated donors. The extent to which unrecognized mismatching for alleles that encode DR1-DR18 contribute to the increased risk of acute GVHD and overall survival is unknown. We analyzed 364 patients and their HLA-A, B, DR serologically matched donors to determine whether molecular typing of DRB1 alleles can allow more accurate donor/recipient matching and thereby improve clinical outcome after marrow transplantation. DRB1 alleles were typed by sequence-specific oligonucleotide probe hybridization methods. Selected alleles were confirmed by DNA sequencing. Of the 364 pairs, 305 were matched and 59 were mismatched for DRB1. The probability of moderate to severe acute GVHD was .48 for the matched and .70 for the mismatched patients. Compared with mismatched patients, the estimated relative risk (RR) of GVHD for matched patients was .58 (95% confidence interval [CI], .40 to .85). DRB1 matching decreased the risk of transplant- related mortality (RR, .66; 95% CI, .44 to .97) and was associated with decreased overall mortality (RR, .71; 95% CI, .51 to 1.0). Therefore, matching DRB1 alleles of the donor and recipient decreases the risk of acute GVHD and improves survival after unrelated marrow transplantation. These results indicate that prospective matching of patients and donors for DRB1 alleles is warranted.     

Systemic lupus erythematosus, thrombocytopenia, microangiopathic haemolytic anaemia and anti-CD36 antibodies [clinical conference]

Thrombocytopenia in patients with acute systemic lupus erythematosus (SLE) frequently presents the clinician with considerable diagnostic and therapeutic difficulties. In this Grand Round, we present a 48-yr- old woman with a 7 yr history of lupus, who presented with acute proliferative glomerulonephritis and nephrotic syndrome, pneumonia, profound hypocomplementaemia and a severe microangiopathic haemolytic anaemia with associated thrombocytopenia. Her thrombocytopenia proved initially refractory to conventional immunosuppressive therapy, and corticosteroids, and resolved only with plasma exchange and repeated fresh frozen plasma infusions. Serological testing revealed high-titre antinuclear antibodies (ANA) and markedly raised antibodies to double- stranded (ds) DNA, but no significant elevation in anticardiolipin antibodies. Platelet-associated IgG and IgM and antibodies to the CD36 glycoprotein antigen, expressed on platelets and endothelium, were detected in the serum. We address some of the difficult diagnostic and management issues raised by this complex patient and the possible immunopathological links between antibodies to CD36, immune-mediated red cell destruction, thrombocytopenia and thrombotic microangiopathic haemolytic anaemia.      

Acute monoblastic leukemia in infancy and early childhood: successful treatment with an epipodophyllotoxin

Four of five infants and young children with acute monoblastic leukemia, a disease that heretofore has been highly refractory to therapy, were successfully treated with sequential infusions of a podophyllin derivative employed as a single agent over a protracted period of time. In three of the five children, monocytic leukemia cutis was present at birth. Treatment was begun in two of them when the disease had progressed to systemic involvement at a few months of age, and in the third when disease was still localized. The other two children were 11 and 18 months of age at initial presentation with widespread disease. Four children are off therapy 11 months, 26 months, 5 years, and 6 years, respectively.     

Partial plasma exchange using albumin replacement: removal and recovery of normal plasma constituents

Using albumin and crystalloid as the only replacement fluids, the effect of partial plasma exchange on the removal and recovery of normal plasma constituents was studied. The results of 30 procedures on 10 individuals were evaluated. Four patterns of removal are described: reduction in the concentration of fibrinogen and C3 were greater than would be expected based upon the extent of the exchange, while IgG, IgM, cholesterol, alkaline phosphatase and SGPT were removed as expected. Reduction of serum glutamicoxalacetic transaminase (SGOT), lactate dehydrogenase (LDH), amylase, and creatine phosphokinase (CPK) averaged 17% less, and uric acid, calcium and K+ averaged 53% less than expected. Concentrations of HCO-3 and glucose did not change. The mean recovery for all constituents except fibrinogen, C3, cholesterol. IgG and IgM was near 100% at 48-72 hr postpheresis. The 72-hr recovery of fibrinogen and complement was 66% and 60%, respectively. Cholesterol recovery was also slow, requiring a minimum of 1 wk to reach prepheresis levels. Measured at a time when quantitative IgM levels were still reduced, alloantibody agglutinating activity (anti-A and anti-B) in a postpheresis sample exceeded prepheresis agglutinating activity. These data demonstrated that, depending upon quantity and frequency of pheresis, partial plasma exchange using albumin replacement may cause progressive marked reduction in concentrations of immunoglobulin, complement, fibrinogen, and cholesterol. Furthermore, newly synthesized antibody may have increased biologic activity.     

Extended long-term culture reveals a highly quiescent and primitive human hematopoietic progenitor population

Long-term culture-initiating cells (LTC-IC) are hematopoietic progenitors able to generate colony-forming unit-cells (CFU) after 5 to 8 weeks (35 to 60 days) of culture on bone marrow (BM) stroma and represent the most primitive progenitors currently detectable in vitro. We have recently reported that long-term cultures initiated with CD34+CD38- cells from BM or cord blood are able to continue generating CFU for at least 100 days, ie, beyond the standard LTC-IC period. In this report, single-cell cultures from cord blood and retroviral marking of cord blood and BM were used to study whether the subpopulation of CD34+CD38- cells able to generate CFU beyond 60 days ("extended long-term culture-initiating cells" or ELTC-IC) are functionally distinct from LTC-IC in terms of timing of initial clonal proliferation and generative capacity. All cord blood LTC-IC formed clones of greater than 50 cells by day 30. In contrast, cord blood ELTC- IC proliferated later in culture, 50% forming clones after day 30. Although efficient retroviral marking of LTC-IC was seen (25% to 45%), marking of ELTC-IC was inefficient (< 1%), consistent with a more quiescent progenitor population. There was a positive correlation between time of clonal proliferation and generative capacity. ELTC-IC generated threefold to fourfold more progeny than did LTC-IC (P < .002). These studies show that there is a functional hierarchy of progenitors in long-term culture which correlates with their level of quiescence. By extending the LTC-IC assay, a more primitive progenitor may be studied that may be functionally closer to the human long-term repopulation stem cell in vivo.     

Treatment of two patients with B cell lymphoma with monoclonal anti- idiotype antibodies

Mouse monoclonal anti-idiotype antibodies have been used to treat two patients with progressive advanced B cell non-Hodgkin's lymphoma. Transient falls in the level of circulating malignant cells and idiotypic immunoglobulin were produced, and free unbound monoclonal antibody was identified in the serum. Homing of the antibodies to tumor cells in the blood, bone marrow, ascites, and lymph nodes was demonstrated in both patients. Although large amounts of anti-idiotype antibody were given (3.8 g and 5.8 g), no toxic effects were seen, and no antibodies to the foreign mouse protein were made. There was no modulation of the antigen from the tumor cells and no indication of immunoselection. There was evidence of large-scale tumor cell destruction, but only a modest reduction in tumor size. The killing of the tumor cells was mediated by the reticuloendothelial system and not by complement.     

Biologically active thrombomodulin is synthesized by adherent synovial fluid cells and is elevated in synovial fluid of patients with rheumatoid arthritis

Thrombomodulin (TM) is a transmembrane glycoprotein that interacts with thrombin, thereby serving as a cofactor in the activation of protein C, a major physiologically relevant natural anticoagulant. Although initially described as a vascular endothelial cell receptor, TM has also been reported to be synthesized by several cells, including megakaryocytes, platelets, monocytes, neutrophils (PMN), mesothelial cells, and synovial lining cells. A prominent feature of rheumatoid arthritis (RA) is infiltration of PMN into the joint space. To determine whether TM might play a role in the inflammatory process, we examined synovial fluid for the presence of TM in 10 patients with RA and five patients with osteoarthritis (OA). We determined that the mean synovial fluid and plasma TM levels in the OA group were 23.5 ng/mL and 24.2 ng/mL, respectively, whereas those with RA had a significantly elevated mean synovial fluid TM level of 136.2 ng/mL as compared with the plasma TM concentration of 43.9 ng/mL (P < .05). Synovial fluid TM levels did not correlate with PMN counts (r = .261). Purified TM from synovial fluid was identical in molecular weight to plasma-derived TM and was biologically functional with respect to protein C cofactor activity. Using direct immunofluorescence, we determined that adherent cultured synovial fluid cells that are not monocytoid in origin express surface and cytoplasmic TM, thereby providing an alternative source of the protein. Biologic activity of the cell-surface TM was confirmed by acceleration of thrombin-dependent protein C activation. Northern analysis of RNA extracted from the cultured cells indicated that TM messenger RNA was present, suggesting local synthesis. Our results indicate that in RA-associated synovial effusions, biologically active TM is increased, the source of which may be from plasma, PMN, and/or synovial lining cells. TM may play a regulatory role either in fibrin deposition in the inflamed joint and/or in the progression of the inflammatory process.