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Biomedical subjects

M Teodorescu

Publications and source records attributed to M Teodorescu.

At least 73 records · Page 4Linked to original sources
PubMed1979

Dependence of lymphocyte surface Ig on continuous polyclonal activation.

We have previously shown that most rabbit splenic B cells cultured in a medium supplemented with 5% autologous serum require continuous polyclonal stimulation to maintain detectable amounts of surface Ig. In the absence of this stimulation B cells shed but do not replace their surface Ig. Here, we investigated the mechanism responsible for the loss or maintenance of surface Ig. We showed that the addition of inhibitors of mRNA and protein synthesis to the cell cultures completely abolished the Ig maintenance effect provided by the mitogen thereby suggesting that it did not act by 'freezing' the membrane Ig but rather by continuously stimulating resynthesis. Moreover, by labelling the surface Ig with 125I-labelled Fab anti-allotype antibody we showed that the maintenance of surface Ig by mitogen stimulation was due to the turnover of surface Ig. The cells shed and replaced their surface Ig with a half-life of about 2 h only when mitogen was present but shed without replacing the surface Ig in the absence of mitogen. Also, the B-cell mitogens, SM and LPS, were able to maintain surface Ig even at extremely small concentrations while the T-cell mitogens, Con A and PHA, failed to do so at any concentration, suggesting that direct stimulation of B cells was needed to maintain surface Ig. When spleen cells were cultured in 'crowded' conditions in the absence of mitogen they did not lose their surface Ig; under these conditions it appeared that a factor associated with the macroglobulin fraction is induced and acts in the same manner as a B-cell polyclonal activator to maintain the turnover of surface Ig. Such a factor may actually function in vivo since lymphocytes are in very close contact in the lymphoid organs. We concluded that rabbit B lymphocytes shed and replace their surface Ig with a half-life of about 2 h and that the replacement, but not the shedding of surface Ig, is dependent on continuous exogenous or endogenous polyclonal activation.

Animals↗
PubMed1979

Functional characterization of mouse lymphocyte subpopulations identified by their natural binding of bacteria. I. Identification of the Ig-secreting cell subpopulation.

Three mouse B cell subpopulations (B1, B2 and B3) can be identified by their natural binding of bacteria. To determine whether these subpopulations have unique functions, we assayed the number of anti-SRBC-secreting cells and the number of Ig-secreting cells in unseparated populations and in populations in which the B2 and B3 cells were removed by immobilized monolayers of Escherichia coli-2, a bacteria that binds B2 and B3 cells. Essentially all of the plaque forming cells present in the unseparated population were found in the B1-enriched population, suggesting that most of the antibody-secreting and Ig-secreting cells were in the B1 subpopulation. To show conclusively that the anti-SRBC-secreting cells resided in the B1 subpopulation, the Jerne plaque assay was performed on slides by using lymphocytes prelabeled with various bacteria and the cells that gave rise to the plaques were directly examined. Essentially all of the secreting cells were labeled with Corynebacterium xerosis, which binds to the B1 and B2 cells, whereas very few of the secreting cells were labelled with Arizona hinshawii, which binds to the B2 cells, or with Escherichia coli-2, which binds to the B2 and B3 cells. Thus, the B1 subpopulation contained essentially all of the antibody-secreting cells, which indicates that the B cell subpopulations identified by bacteria are functionally different.

Animals↗
PubMed1977

Enumeration and identification of human leukemic lymphocytes by their natural binding of bacteria.

The recently described property of bacteria to bind to human lymphocytes was used to distinguish between normal and chronic leukemic lymphocyte (CLL) populations. Strains of the following bacteria were used in this study: Arizona hinshawii, Escherichia coli strains 1 and 2, Bacillus globigii, Brucella melitensis, Corynebacterium diphtheriae strains 1 and 2, Corynebacterium xerosis, Sarcina lutea, Staphylococcus aureus, and Staphylococcus epidermidis. For identification of immunoglobulin-bearing lymphocytes, a strain of E. coli that did not bind to human lymphocytes was coated with anti-human light-chain antibody. Labeling of lymphocytes with bacteria was promoted by centrifugation. In the eight CLL patients studied, in which greater than 90% of the lymphocytes were leukemic cells, 52 to 77% were labeled by anti-human light-chain antibody-E. coli, 80 to 93% were labeled by Br. melitensis, and 78 to 95% were labeled by E. coli 1 compared to 11 to 24, 11 to 22, and 30 to 44%, respectively, in normal individuals, Thus, Br. melitensis, E. coli 1, and the anti-human light-chain antibody-E. coli may have diagnostic value for CLL. The percentage of the lymphocyte population that bound each of the other bacteria varied from patient to patient. Preliminary results obtained by studying the pattern of binding of E. coli 2, B. globigii, Sa. lutea, or S. aureus by leukemic lymphocytes suggest that categories of CLL patients may be distinguished by this method.

Antibodies, Anti-Idiotypic↗
PubMed1976

Immunoglobulin content and antibody activity in an artificial body cavity.

Artificial body cavities (ABC) were created by the insertion of hollow polyethylene balls in the subcutaneous tissue of rabbits. After two months no inflammatory reaction could be detected, the ABC was enveloped by a membranous structure, and the cavity contained about 20 ml of fluid. The protein concentration was about 3 times, and the IgG about 8 times, lower in the ABC fluids than in the corresponding serum. At the same time the antibody titers against sheep red blood cells (SRBC), human IgG and herpes simplex virus type 1 (HSV) were about 20 200 times lower than in the corresponding serum samples. The IgG molecules appeared to be undamaged as shown by the presence of various allotypes and by the elution pattern from G-200 column. Testing the protective activity of ABC fluids and of serum against HSV infection showed that ABC fluids had no protective activity. The experiments suggest that the membranous structure selected among classes of Ig and probably among other serum proteins. In addition, the IgG molecules with antibody activity against various inoculated antigens were selectively excluded to penetrate in the ABC. The ABC might be considered analogous to virtual cavities of the body surrounded by membranes and possibly to the extravascular compartment.

Animals↗
PubMed1976

Enumeration and isolation of rabbit T and B lymphocytes by using antibody-coated erythrocytes.

Rosette formation with antibody-coated erythrocytes (Ab-E) was employed for the enumeration and isolation of rabbit B cells (Ig+T-) and T cells (Ig-T+). The cells bearing surface Ig (Ig+ cells) were enumerated by a direct immunocytoadhesion technique utilizing anti-rabbit IgG antibody-coated erythrocytes (Ab-E). To enumerate cells bearing thymus cell antigen (T+ cells), an indirect rosette technique was used in which lymphocytes were first sensitized with guinea pig anti-rabbit thymus cell antiserum and then rosetted with anti-guinea pig IgG Ab-E. To demonstrate the specificity of the anti-thymus cell antiserum, a 51Cr radioimmunoassay for counting rosettes was employed along with visual counting to enumerate Ig+ and T+ cells in lymph node cell populations. When Ig+ and T+ lymph node cells were rosetted simultaneously with sheep and human erythrocytes, no mixed rosettes (less than 1%) were observed. Ficoll-Hypaque gradient centrifugation was used to obtain purified Ig+T- and Ig-T+ cells by removing rosetted T+ and Ig+ cells, respectively. The purity of isolated Ig-T+ cells was indicated by 94 to 95% indirect rosetting with anti-thymus cell antiserum and by 0 to 3% direct rosetting with anti-rabbit IgG Ab-E. The purity of isolated Ig+T- cells was indicated by 90 t0 94% direct rosetting with anti-rabbit IgG Ab-E and by 2 to 3% indirect rosetting with anti-thymus cell antiserum. The percentage of Ig+T- and Ig-T+ cells were determined in peripheral blood and in various lymphoid organs. The isolated Ig+T- and Ig-T+ cells were also characterized by their responses to mitogens. Thus, nearly pure Ig+T- and Ig-T+ cells were isolated by "negative selection," which should minimize functional changes of the cells, and thereby facilitate the study of their biologic properties, e.g., their response to mitogens.

Animals↗
PubMed1975

A simple radioimmunoassay for the enumeration of rosette-forming cells.

A simple radioimmunoassay for the enumeration of Ig bearing (Ig+) lymphocytes by rosette formation with anti-Ig, antibody coated erythrocytes (Ab-E) is described. The method is based upon labeling lymphocyte populations with 51Cr, rosetting them with Ab-E, separating the rosetted from unrosetted cells by centrifugation through a Ficoll-Hypaque layer, counting the radioactivity of the unrosetted cells, and counting the radioactivity of the unrosetted cells in a rosetting system with unreactive uncoated-E. This permits the calculation of the percentage of rosette-forming Ig+ cells. The assay eliminates the subjectivity and tediousness of counting and distinguishing between rosetted and unrosetted cells under the microscope. Being also sensitive and reliable, this radioimmunoassay may, after suitable modifications, replace the conventional counting of other types of rosettes.

Animals↗
PubMed1975

Maintenance of lymphocyte surface Ig by mitogen stimulation in vitro.

In 4 to 24 hr cultures of rabbit lymphoid cells in medium supplemented with autologous serum, most B cells lost their surface Ig as assayed by rosette formation with anti-Ig antibody-coated erythrocytes. This loss was prevented by adding selected mitogens such as streptococcal mitogen (SM), lipopolysaccharide, and concanavalin A or by supplementing the medium with fetal calf serum. When SM was added at various times to the cultures (1, 2, 3, and 4 hr), it was effective in maintaining the approximate level of Ig-bearing cells present at the time of its addition but was ineffective in restoring the level of Ig-bearing cells present at the time the cultures were intiated. Very small, submitogenic doses of SM were sufficient to maintain the level of Ig-bearing cells. The data suggest that lymphocytes require continuous stimulation to maintain their surface receptors.

Animals↗
PubMed1975

The influence of smallpox revaccination upon the foetus.

Serological, virological, anatomo- and histopathological investigations were performed in pregnant women subjected to smallpox revaccination. Serological findings were normal; no vaccinia virus was isolated from 210 placentae collected upon therapeutical abortion. Anatomopathological investigation of 15 placentae showed various lesions, while the embryo were free from any histopathological changes. The data prove that smallpox immunization does not affect the embryo directly, but only through the placenta.

Adult↗
PubMed1975

Enumeration and isolation of human T and B lymphocytes by rosette formation with antibody-coated erythrocytes.

Rosette techniques are presented for the enumeration and separation of both Ig+ T- and Ig- T+ human lymphocytes. In order to enumerate Ig+ cells, the direct immunocytoadhesion technique was employed using human erythrocytes (E) coated with purified anti-kappa or anti-lambda light chain antibodies. Specificity of these rosettes was shown with chronic lymphocytic leukaemias of either the kappa or lambda type. T+ cells were enumerated by a new indirect rosette technique in which the lymphocytes were initially treated with rabbit anti-human thymus cell antiserum followed by direct rosetting with human E coated with purified anti-rabbit light chain antibody. For normal individuals, 24-32% Ig+ T- cells and 65-71% Ig- T+ cells were found among the lymphocytes of peripheral blood as well as tonsils with these rosette methods. The Ficoll-Hypaque method was used to obtain purified Ig- T+ and Ig+ T- cells by removing rosetted Ig+ cells or T+ cells, respectively. The purity of the Ig- T+ cells was indicated by greater than 99% indirect rosetting of cells sensitized with anti-human thymus cell antibody (Ab) and by less than 1% direct rosetting with anti-kappa Ab-E+ anti-lambda Ab-E. The purity of the Ig+ T- cells obtained was indicated by 92-96% direct rosetting with anti-kappa Ab-E+anti-lambda Ab-E and by less than 1% indirect rosetting with anti-human thymus cell antibody. A small percentage of Ig- T- 'null' cells could not be identified by either reagent. Thus, essentially pure Ig- T+ and Ig+ T- cells were readily and efficiently isolated by 'negative selection' thereby lessening the possibility of functional changes that may develop by more extensive manipulation of lymphocytes.

Antibodies↗