Evidence for a change in the expression of beta2-microglobulin-assoicated membrane structures on leukaemic human cells.

Cell-associated and serum beta2-microglobulin was estimated in seven patients with chronic lymphocytic leukaemia. The amount of cell-associated beta2-microglobulin was significantly reduced (P less than 0.01), due to a decrease in the fraction of beta2-microglobulin that passes unretarded through a concanavalin A affinity column (presumably non-HLA-associated beta2-microglobulin). Serum concentrations of beta2-microglobulin were increased, but no correlation was found between the decrease in cell-associated beta2-microglobulin and the increase in serum beta2-microglobulin. All of the beta2-microglobulin from leukaemic serum was eluted corresponding to a molecular weight of 11,800 and none of it was retarded on a concanavalin A affinity column. The decrease in cell-associated beta2-microglobulin might reflect a change in the qualitative or quantitative expression of beta2-microglobulin-associated membrane structures on the leukaemic cells, perhaps conferring resistance to the cells against hypothetical immunological host defence mechanisms.     

The receptor for urokinase-type plasminogen activator and urokinase is translocated from two distinct intracellular compartments to the plasma membrane on stimulation of human neutrophils

The cellular receptor for urokinase-type plasminogen activator (uPAR) binds pro-urokinase (pro-uPA) and facilitates its conversion to enzymatically active urokinase (uPA). uPA in turn activates surface- bound plasminogen to plasmin, a process of presumed importance for a number of biologic processes including cell migration and resolution of thrombi. We have previously shown that uPAR is expressed on the plasma membrane of circulating neutrophils, and we now report that stimulation with phorbol myristate acetate (PMA), FMLP, or tumor necrosis factor- alpha results in a rapid increase in the expression of uPAR. This process is accompanied by an increased cell-associated plasminogen activation after preincubation of neutrophils with pro-uPA in vitro. By subcellular fractionation of unstimulated neutrophils, 50% of uPAR is recovered in fractions containing latent alkaline phosphatase, corresponding to an intracellular compartment of easily mobilizable secretory vesicles distinct from both primary and specific granules, whereas the remaining 50% of uPAR is associated with a compartment eluting close to the specific granules. In contrast, the ligand pro-uPA is primarily (approximately 80%) found in the specific granules, but small amounts of pro-uPA/uPA (approximately 20%) coelute with latent alkaline phosphatase. Stimulation of neutrophils with FMLP results in translocation of uPAR as well as of pro-uPA from the secretory vesicles, whereas stimulation with PMA is required to translocate material from specific granules. Flow cytometry of neutrophils saturated with exogenous diisopropyl fluorophosphate-uPA shows a large excess (approximately 90%) of unoccupied uPAR on resting as well as FMLP- and PMA-stimulated neutrophils, suggesting a possible role for exogenous pro-uPA in providing neutrophils with a potential for plasminogen activation. These processes may be important for neutrophil extravasation and migration through extracellular matrix and for the contribution of neutrophils to resolution of thrombi.     

Expression of an antigen defined by a monoclonal antibody (SA-1) on normal and malignant cells

A monoclonal antibody (SA-1) has been characterized. The antibody was derived from the fusion of the X-63 myeloma cell-line with splenocytes from a mouse immunized with human acute megakaryoblastic leukaemia cells. The antibody reacted with blast cells from 65% of patients with AML without correlation to morphologic classification. The antibody further reacted with a subset of myeloid cells from normal bone marrow, and with peripheral neutrophil granulocytes. In lymph nodes the antibody showed reactivity with subsets of dendritic reticulum cells. In skin biopsies the antibody reacted with subsets of Langerhans cells, subsets of indeterminate cells and activated T-lymphocytes. The antigen was not expressed on non-activated T-lymphocytes. Neither was it expressed on B-lymphocytes, erythrocytes, platelets nor blast cells from patients with ALL. The antigenic target for the antibody SA-1 was a surface exposed polypeptide (mol. wt. 15 000 D).     

The receptor for urokinase-type plasminogen activator is deficient on peripheral blood leukocytes in patients with paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal defect in bone marrow-derived cells and is clinically associated with intravascular hemolysis, hemoglobinuria, and an increased frequency of venous thrombosis. The common denominator of PNH-affected blood cells appears to be a defect in the membrane attachment of proteins normally anchored by glycosyl-phosphatidylinositol (GPI). We report here that the cellular receptor for urokinase-type plasminogen activator (u-PAR) is deficient on affected peripheral blood monocytes and granulocytes from four individuals with PNH as evidenced by chemical cross-linking analysis as well as by immunofluorescence flow cytometry using a monoclonal anti-u-PAR antibody. In contrast, on normal blood monocytes and granulocytes we find significant amounts of u-PAR, which is attached to the plasma membrane by a GPI-anchor as defined by its sensitivity towards a specific phospholipase treatment. By two-color flow cytometry it was shown that deficiency of u-PAR expression paralleled that of another GPI-anchored protein. As u-PAR is involved in the initiation of pericellular proteolysis, the reduced expression of u-PAR on PNH-affected leukocytes led to an overall reduction in the capacity for plasminogen activation by cell-surface-bound urokinase. Whereas the abnormal susceptibility of PNH-affected erythrocytes to lysis by autologous complement has been related to the low expression of three GPI-anchored complement regulatory proteins on the cell surface, we now propose that lack of u-PAR expression on the surface of peripheral blood leukocytes may be causally related to the high incidence of venous thrombosis observed in PNH patients.     

The seroepidemiology of rubella in western Europe

Most of the countries in western Europe have now implemented mass infant rubella immunization programmes, instead of or in addition to selective vaccination in order to achieve the elimination of congenital rubella syndrome. The European countries Denmark, England and Wales, Finland, France, Germany, Italy and the Netherlands undertook large, national serological surveys collecting several thousand serum specimens during 1994-8. Antibodies against rubella virus were detected by a variety of enzyme immuno-assays. Comparability of the assay results was achieved by a standardized methodology. The age- and sex-stratified serological results were related to the schedules, coverage of rubella vaccination and the incidence in these countries. The results show widely differing levels of immunity to rubella both in the general population and in the specific age groups of males and females. A low rate (< 5%) of susceptibles in childhood and adolescents of both sexes was obtained only in Finland and the Netherlands. Countries such as Italy with only moderate coverage for the infant immunization programme currently have both high susceptibility levels in the general population and in the at-risk population. The likelihood is of continued epidemics of rubella with cases of congenital rubella syndrome. The continued implementation of selective vaccination will help to offset the impact of this ongoing transmission and to protect women on reaching childbearing age.     

In B-cell chronic lymphocytic leukaemia chromosome 17 abnormalities and not trisomy 12 are the single most important cytogenetic abnormalities for the prognosis: A cytogenetic and immunophenotypic study of 480 unselected newly diagnosed patients

Of 560 consecutive, newly diagnosed untreated patients with B CLL submitted for chromosome study, G-banded karyotypes could be obtained in 480 cases (86%). Of these, 345 (72%) had normal karyotypes and 135 (28%) had clonal chromosome abnormalities: trisomy 12 (+12) was found in 40 cases, 20 as +12 alone (+12^single), 20 as +12 with additional abnormalities (+12^complex). Other frequent findings included abnormalities of 14q, chromosome 17, 13q and 6q. The immunophenotype was typical for CLL in 358 patients (CD5⁺, Slg^weak, mainly FMC7⁻) and atypical for CLL in 122 patients (25%) (CD5⁻, or Slg^strong or FMC7⁺). Chromosome abnormalities were found significantly more often in patients with atypical (48%) than in patients with typical CLL phenotype (22%) (P < 0.00005). Also +12^complex, 14q +, del6q, and abnormalities of chromosome 17 were significantly more frequent in patients with atypical CLL phenotype, whereas +12^single was found equally often in patients with typical and atypical CLL phenotype. The cytomorphology of most of the +12 patients was that of classical CLL irrespective of phenotype. In univariate survival analysis the following cytogenetic findings were significantly correlated to a poor prognosis: chromosome 17 abnormalities, 14q +, an abnormal karyotype, +12^complex, more than one cytogenetic event, and the relative number of abnormal mitoses. In multivariate survival analysis chromosome 17 abnormalities were the only cytogenetic findings with independent prognostic value irrespective of immunophenotype.We conclude that in patients with typical CLL immunopenotype, chromosome abnormalities are somewhat less frequent at the time of diagnosis than hitherto believed. +12^single is compatible with classical CLL, and has no prognostic influence whereas chromosome 17 abnormalities signify a poor prognosis. In patients with an atypical CLL immunophenotype, chromosome abnormalities including +12^complex, 14q +, del 6q and chromosome 17 are found in about 50% of the patients, and in particular chromosome 17 abnormalities suggest a poor prognosis.     

Successful nonsibling bone marrow transplantation in severe combined immunodeficiency.

Severe combined immunodeficiency (SCID) was diagnosed in a girl immediately after birth; her older brother had SCID and was successfully reconstituted by bone marrow transplantation from his uncle. She was isolated in a laminar air flow bench and decontaminated. The father differed by one HLA-A antigen but was HLA-Dw2 homozygous like the patient; his lymphocytes showed a slight response to the patient's cells in mixed lymphocyte culture (MLC). At the age of 2 1/2 months and again at 5 months, she was given a bone marrow transplant from the father. During the entire course the patient had no infections, and apart from a transient eosinophilia she had no signs of graft-versus-host reaction. Immunological reconstitution was nearly complete at 9 months of age, when she was recontaminated. One year later plasma immunoglobulin concentrations are in the low normal range (IgG and IgM) or decreased (IgA); tests of cell-mediated immunity are normal. Apart from slight upper respiratory infections, the patient has been healthy. Physical and psychological development have been normal.     

A role of late Epstein-Barr virus infection in multiple sclerosis

OBJECTIVE: To assess Epstein-Barr virus (EBV) seroconversion in a high multiple sclerosis (MS) prevalence area and to evaluate the recall of diagnosed infectious mononucleosis in MS patients. METHODS: The study was based on information or blood samples, or both, from schoolchildren, young MS patients and matched controls. EBV serology was performed on 1154 blood samples. RESULTS : We demonstrate that more than one third of the population in a high MS prevalence area is seronegative to EBV at puberty. This is in contrast to the virtually complete seroconversion to EBV early in life in individuals from areas with a low prevalence of MS. Furthermore, we demonstrate that recall of diagnosed infectious mononucleosis (IM), but not recall of common childhood diseases, is significantly more frequent among MS patients than healthy controls. All MS patients, including patients without prior immunosuppressive treatment, were EBV seropositive. CONCLUSION: During or after puberty, EBV is transmitted to a major proportion of the population in an MS high-prevalence area. Together with our previous documentation of an association between late infection with EBV and an increased risk of developing MS, these data support a role of EBV infection in MS.     

Beta-2-microglobulin review: its relevance in clinical oncology

Beta-2-microglobulin (beta 2-m) is an intrinsic part of the HLA system and is most probably involved in cell recognition. The levels of free beta 2-m in the blood and urine are influenced by beta 2-m production and its clearance and destruction in the kidney. Many tumors can be associated with an elevated serum beta 2-m, the reason is unknown. The most promising application of beta 2-m as a tumor marker would appear to be lymphoid malignancies, especially multiple myeloma and chronic lymphocytic leukemia.     

Modification of beta-2-microglobulin in sera from patients with small cell lung cancer: evidence for involvement of a serine protease.

Modification of beta-2-microglobulin has been shown to occur in vitro in serum of patients suffering of small cell lung cancer, where it clearly correlated to the clinical course of disease. The cause of serum beta-2-microglobulin modification occurring in these patients is investigated in the present study. This revealed that modification of beta-2-microglobulin is due to cleavage by a serine protease, which is dependent on divalent cations and has a trypsin-like specificity. The process showed the following characteristics: pH optimum at 8.5, heat inactivation by incubation at 56 degrees C for 20 min and temperature optimum at 20 degrees C.