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Biomedical subjects

G Mota

Publications and source records attributed to G Mota.

14 recordsLinked to original sources
PubMed1996

Mouse multivalent IgG(2a, b) antibody--ricin A-chain immunotoxins combined with homologous or heterologous interleukin 2 in the treatment of a murine malignant lymphoproliferation (EL4).

Two immunotoxins containing ricin A-chain, staphylococcal protein A and mouse anti-Thy 1.2 antibodies of IgG(2a,b) subclass, were prepared. The two multivalent immunotoxins of 750 and 370 kDa and molar ratio A-chain: IgG of 1:2, were used for the treatment of mice bearing ascitic EL4 lymphoma. The immunotoxin-treatment, performed intraperitoneally, was combined or not with homologous or heterologous interleukin 2. The antitumor effects expressed by increase of mice survival time (p < 0.001 as compared with nontreated animals) corresponded to a proportion of 88-90% lymphoma cell-kill by immunotoxin and 93-95% by combination treatment (immunotoxin + interleukin 2), as calculated from the relationship between the survival time of nontreated mice and the number of tumor cells inoculated.

Animals↗
PubMed1991

Interleukin 2 enhances the efficiency of immunotoxins in the treatment of mice with ascitic tumors.

Two multivalent immunotoxins (ITs) with cytotoxic potential against Thy 1.2-expressing tumor cells were used in association with mouse interleukin 2 (IL2) for treatment of mice bearing ascitic EL4 lymphomas. The combined treatment, ITs + IL2, induced an enhanced antitumor effect revealed by a significant prolongation of the survival time of mice as compared to the simple treatment with ITs or IL2 alone. According to the survival of mice treated by combined therapy, the proportion of killed tumor cells rose up to 94% as resulted from the dose-dependent curve of the survival of nontreated mice versus the number of tumor cells inoculated.

Animals↗
PubMed1990

Treatment of murine EL4 leukemia in ascitic form with anti-Thy 1.2 specific immunotoxins.

C57BL/6 mice with EL4 leukemia cells in ascitic form were intraperitoneally treated with ricin A chain-multivalent antibody immunotoxins. The immunotoxins containing rabbit IgG anti-Thy 1.2 antibodies complemented by protein A of Staphylococcus aureus were able to interact specifically with the target cells and to induce an antitumor effect as revealed by an increase in survival time of the mice. No apparent secondary effects consecutive to a cytotoxic action on the normal Thy 1.2 antigen bearing cells were observed with the immunotoxin doses used.

Animals↗
PubMed1987

Binding and cytotoxic effect of ricin toxin on multivalent hybrid antibody-coated target cells.

Multivalent hybrid antibodies with dual specificity were prepared by cross-linking with protein A two antibodies of different specificity, one against ricin toxin and the other against the H-2 antigens of murine leukemia EL4 cells. This bifunctional antibody specifically attached to EL4 cells was able to capture ricin toxin (RcA2) molecules with an affinity 20 times higher than that of the galactose-containing glycoproteins of the cell surface (nonspecific binding). The hybrid-bound RcA2 gained access into the target cell cytoplasm by endocytosis and blocked [3H]thymidine incorporation as efficiently as free RcA2 does on nontreated EL4 cells (3.3 X 10(-11) M). These results indicate that multivalent hybrid antibody, easy to prepare in purified form and endowed with high affinity for both target cell and ricin toxin, may be utilized efficiently for the specific delivery of toxins to target cells.

Animals↗
PubMed1984

Selective affinity of protein A containing staphylococci for monomeric and polymeric IgG.

Protein A containing staphylococci were saturated with human monomeric IgG (mIgG) and cross-linked with glutaraldehyde. The resulting material (SMG) preferentially bound aggregated IgG (aIgG) and soluble immune complexes (CIC). One milliliter of a 10% suspension of SMG bound approximately 30 micrograms of mIgG and 1000 micrograms of aIgG and CIC. The binding of aIgG to SMG was reduced to approximately 50% at a 20-fold excess of mIgG over aIgG. CIC and aIgG could be released from SMG by elution with 3 M KSCN. The results indicate that SMG can be used for identification and removal of CIC in patient plasma.

Antigen-Antibody Complex↗
PubMed1982

Fc receptor for IgA on erythrocytes.

Fc receptor for human IgA was detected on rabbit, sheep and human ORh- red blood cells. This Fc alpha receptor was able to bind human secretory or myeloma IgA, IgA1 or IgA2 and alpha chains. The ligand binding was detected by complement mediated lysis and agglutination with specific anti-IgA serum. Blocking experiments showed the inability of Fab(IgA) fragment or of secretory component to inhibit the IgA binding.

Animals↗
PubMed1982

Specific cytotoxic activity of normal T-lymphocytes coated with multivalent hybrid antibody.

Mouse lymphoid cells treated with multivalent hybrid antibody consisting of rabbit IgG anti-T antibody and rabbit IgG anti-chicken red blood cell antibody formed rosettes and killed specifically chicken red blood cells. The attachment and killing of chicken red blood cells is due to multivalent hybrid antibody which is able to link with one antibody specificity (anti-T) the T-lymphocytes and with the other one the chicken red blood cell surface antigen(s). Some indirect results seem to suggest natural killer cells as a candidate for the multivalent hybrid antibody-induced cytolytic effects. Multivalent hybrid antibody can be a useful alternative to mitogen for assaying specifically the cytotoxic potential of various cell populations pre-existing in normal organisms and requiring only a link to the target cells to reveal their killing ability.

Animals↗
PubMed1982

Receptors for IgA on human thymus cells in myasthenia gravis.

Specific surface receptors for the Fc region of human immunoglobulin A (Fc alpha R) were identified on the thymus cells of all 15 patients affected by myasthenia gravis. A large variation of the percentage of Fc alpha R bearing thymus cells was recorded (9 . 5-66 . 0%; mean value 27 . 9 +/- 17 . 8) the high values being associated in most cases with the thymus hyperplasia and the low values with a lipomatosis of the organ. Even the lowest percentage of Fc alpha R bearing cells recorded in myasthenia gravis are considerably higher than those found in normal subjects (0 . 4-4 . 1; mean value 1 . 8) demonstrating that the expression of Fc alpha R on the thymus cells is the consequence of the disease. No attempts were made to identify the cell population bearing Fc alpha R but indirect results indicate that the cells belong to E-rosette forming population, and, in some cases, to a null cell population devoid of the ability to form E and EAC rosettes, Fc alpha R can bind various IgA ligands and the binding is confined to a small fraction of IgA (not more than 5%) considered as cytophilic IgA.

Absorption↗
PubMed1981

Simultaneous detection of two different cell surface antigens by electron microscopy by means of multivalent hybrid antibody with double specificity.

Multivalent hybrid antibody (MHA) complexes with dual specificity were prepared by combining two antibodies of different specificities, one against ferritin (Fer), the other against horseradish peroxidase (HRP), with protein A of Staphylococcus aureus (SpA). Electron microscopy of mouse spleen lymphocytes and thymocytes (previously coated with mouse IgG anti-Thy-1 antibody) treated with IgG anti-Fer/SpA/IgG anti-mouse Ig complex and Fer gave better resolution and higher accuracy than previously obtained with IgG anti-HRP/SpA/IgG anti-mouse Ig complex and HRP (Mandache et al., 1980). Surface Thy-1 alloantigen and Fc receptor (charged with human IgG) treated with a mixture of IgG anti-Fer/SpA/IgG anti-Thy-1 and IgG anti-HRP/SpA/IgG anti-human Fab could be simultaneously detected on the thymocyte surface by either light or electron microscopy using Fer and HRP. The concomitant visualization of Thy-1 alloantigen (with Fer) and FcR (with HRP) on mouse thymocyte clearly shows that their distribution is largely independent and that the amount of Thy-1 antigen is greater. These results show that electron microscopy with a mixture of MHA is a useful technique for simultaneous location of two antigenic markers on the cell surface.

Animals↗
PubMed1980

Staphylococcus aureus and protein A as mitogens for rabbit T lymphocytes.

The thymidine uptake by rabbit lymph nodes, spleen and peripheral blood lymphocytes was stimulated by Protein A (SpA) and SpA-containing staphylococci. The cell fraction enriched in T lymphocytes showed a higher degree of stimulation with SpA than the fraction enriched in B cells. Rabbit thymocytes showed a marked thymidine uptake by treatment with SpA but not with staphylococci. The monovalent fragment B of SpA (reacting with IgG) neither stimulated nor inhibited the incorporation of thymidine in rabbit lymph node lymphocytes indicating that the Fc reacting site of SpA cannot be responsible for the mitogenicity.

Animals↗
PubMed1978

Separation of cells by affinity chromatography on SpA-sepharose 6MB.

A cell separation technique was designed which was based on the reaction of protein A of Staphylococcus aureus (SpA) with the Fc regions of IgG antibodies. SpA covalently linked to Sepharose 6MB is able to fix antibody-bearing cells, while non-fixed cells are removed by washing. The fixed cells can be released by dog IgG or by mechanical treatment. As an example of the use of the technique, Ig-bearing cells were isolated from mouse spleen cells treated with rabbit IgG anti-mouse Ig antibody; the purity of the Ig-bearing lymphocytes so isolated was better than 90%. The viability and the ability of the cells to shed the antibodies from their surface were not significantly impaired by the fractionation method. The technique can be generally applied to cell separation providing IgG antibodies against specific surface markers are available.

Animals↗
PubMedDate not supplied

A non-dissociable rabbit IgG-protein a complex.

Glutaraldehyde treatment of rabbit IgG antibody complexed with protein A of Staphylococcus aureus (SpA) enabled the complex (IgG2-SpA1)2 to maintain its molecular weight unchanged and to become non-dissociable at low pH and in excess of IgG. The glutaraldehyde-treated (IgG2-SpA1)2 complex had the same half-life, complement-activating capacity and ability to interact with the Fc receptor as the non-treated complex. Moreover, the glutaraldehyde-treated complex had a stronger immunosuppressive effect on the synthesis of anti-sheep red blood cell antibody than either the non-complexed antibody or the IgG antibody complexed with SpA but untreated with glutaraldehyde.

Animals↗