Monoclonal antibodies to human erythrocyte glucose 6-phosphate dehydrogenase

Generation and characterization of monoclonal antibodies to 28-, 35-, and 65-kilodalton proteins of Mycobacterium tuberculosis

Three monoclonal antibodies (H60.15, H61.3, and H105.10) directed to protein antigens of Mycobacterium tuberculosis were obtained and characterized. H60.15 recognizes a protein with a molecular mass of 28 kilodaltons (kDa) with broad cross-reactivity on a panel of 12 species and strains of mycobacteria. H61.3 reacts with a 35-kDa protein present in M. tuberculosis, Mycobacterium bovis BCG, and M. africanum. On the basis of the antigen molecular masses and competition experiments with other monoclonal antibodies, H60.15 and H61.3 seem to be the first described monoclonal antibodies to these M. tuberculosis proteins. H105.10 binds to the cross-reactive 65-kDa protein present in mycobacteria. Epitope mapping of H105.10 was performed by using the M. leprae DNA sublibrary available in bacteriophage lambda gt11 for this antigen and revealed that its epitope resides in the region from amino acids 20 to 54. The 28-, 35-, and 65-kDa antigens isolated by immunoblotting and presented on nitrocellulose to pleural effusion T cells from tuberculosis patients induced a proliferative response, indicating the presence of T-cell epitopes. These observations indicate that two protein antigens should be added to the list of antigens detectable in M. tuberculosis by monoclonal antibodies. The common feature of such proteins, the elicitation of an immune response of limited or broad cross-reactivity for mycobacteria, encourages the search for their role in the pathogenesis of mycobacterioses.

Activation of NADPH oxidase and phosphorylation of membrane proteins in human neutrophils: coordinate inhibition by a surface antigen-directed monoclonal antibody

Exposure of human neutrophils to low concentrations of phorbol myristate acetate (PMA) results, after a brief lag, in the production of superoxide anion and the phosphorylation of membrane proteins. Evidence that these responses are linked has now been obtained using a monoclonal antibody directed against an undefined macrophage surface antigen. The addition of this antibody, which recognizes a 90 kDa neutrophil membrane protein, caused dose-dependent delays in the onset of both phosphorylation of neutrophil membrane proteins and in the appearance of superoxide anion, following addition of PMA to the cell suspensions. For each response the lag period increased with increasing concentrations of antibody, but the onset of phosphorylation always preceded by a few minutes the initial appearance of superoxide anion.

Monoclonal antibodies in enzyme research: present and potential applications

Hybridoma antibodies are powerful tools. Their impact is already apparent in many areas of basic and applied research. In contrast, their impact is just beginning to be felt in enzymology. The existing literature on monoclonal antibodies to enzymes and isozymes, reviewed in this article, is as yet largely descriptive. However, the potential applications discussed herein promise to revolutionize existing strategies of unraveling the basic biochemistry, immunochemistry, and developmental, somatic cell, and molecular genetics of enzymes and isozymes. At a clinical level, monoclonal antibodies to enzymes promise to radically improve the current modalities of diagnosis and therapy in clinical enzymology and oncology. It is becoming increasingly apparent that the future applications of hybridoma antibodies to enzymes and isozymes appear to be limited only by our imagination.

Binding of monoclonal antibody to cathepsin M located on the external surface of rabbit lysosomes

A monoclonal antibody raised against rabbit liver cathepsin M binds to intact rabbit liver lysosomes. The binding is specific and is abolished by treating the lysosomes with trypsin, which has previously been shown to digest the membrane-bound cathepsin M [S. Pontremoli, E. Melloni, M. Michetti, F. Salamino, B. Sparatore, and B. L. Horecker (1982) Biochem, Biophys. Res. Commun. 106, 903-909]. Rabbit liver lysosomes are adsorbed onto Sepharose 4B coupled to anti-cathepsin M, but not to Sepharose 4B itself or to Sepharose coupled to a nonspecific antibody. The results confirm the location of membrane-bound cathepsin M on the outer surface of the lysosomal membrane.

G6PD Cagliari: a new low activity glucose 6-phosphate dehydrogenase variant characterized by enhanced intracellular lability

A new variant of human erythrocyte glucose 6-phosphate dehydrogenase (G6PD), designated G6PD Cagliari, has been characterized. It is associated with severe enzyme deficiency and can be placed in Class 2 of the usual tabulation of G6PD variants. The specific activity of this variant is near normal, while its decay within the circulating erythrocytes is very rapid compared with normals. Genetic analysis of the family of the propositus indicated that the two available females are heterozygotes characterized by extremely unbalanced mosaic phenotypes.

Monoclonal antibodies to L-asparaginase

Five hybridomas secreting monoclonal antibody to E. coli L-asparaginase were isolated. These monoclonal antibodies were classified into 3 different subclasses; Ig G1 (1 clone), Ig G2 (2 clones) and Ig G3 (2 clones). One of them possessed anti-L-asparaginase neutralizing activity. Four antibodies examined demonstrated a linear Langmuir binding plot and binding affinities, with equilibrium dissociation constant (Kd) ranging between 2.5 X 10(-9) M and 6.3 X 10(-10) M. The monoclonal antibodies should be useful probes for investigation of the enzyme activity.

G6PD Napoli and Ferrara II: two new glucose-6-phosphate dehydrogenase variants having similar characteristics but different intracellular lability and specific activity

Two new glucose-6-phosphate dehydrogenase (G6PD, D-glucose 6-phosphate: NADP oxido reductase, E.C. 1.1.1.49) variants, designated G6PD Napoli and G6PD Ferrara II, are described in propositi from two unrelated families. Characterization side by side of the two variants according to W.H.O. recommendations reveals minor differences which are mostly related to utilization of artificial substrates (increased in both cases as compared with normal G6PD type B). Other properties, which are not significantly distinctive between the two variants, are an enzyme activity amounting to nearly 20% of normal, a decreased electrophoretic mobility, decreased Km values for glucose-6-phosphate and NADP, normal thermostability and biphasic pH curves. However, marked differences emerged between the two variants and between either variant and G6PD B as well, when a number of microtechniques were used. These were: (1) the half-lives of G6PD Napoli and G6PD Ferrara II are 16 and 29 d, respectively, while that of G6PD B is 63 d; (2) the specific activities, measured by a method involving direct estimation of G6PD protein on sodium dodecyl sulphate polyacrylamide gel electrophoretic tracings, are 166 I.U./mg (G6PD Napoli) and 59 I.U./mg (G6PD Ferrara II), as compared with normal value of 180 I.U./mg (G6PD B). On the whole, these findings allow the conclusion that the deficiency of catalytic activity is related to an accelerated though distinctive decay of both mutant enzyme proteins within the affected erythrocytes and that a significant impairment of catalytic efficiency is also involved, as a result of the underlying structural mutation in the case of G6PD Ferrara II.