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Biomedical subjects

T B Tomasi

Publications and source records attributed to T B Tomasi.

At least 19 recordsLinked to original sources
PubMed1979

Immune responses during pregnancy. Evidence of suppressor cells for splenic antibody response.

The primary IgM antibody response to sheep erythrocytes in vivo as well as in vitro is markedly decreased in the spleen cells of pregnant mice, compared to age-matched female controls. Decreased antibody synthesis appears to be mediated by nonspecific suppressor cells, because the addition of pregnant spleen cells to the normal spleen cell cultures causes a significant suppression of plaque-forming-cell responses of the normal spleen cells. Suppressor cell activity was not observed in lymph nodes of pregnant mice. At least two populations of pregnant spleen cells were shown to exert a suppressor cell activity; one is T lymphocytes and the other a nylon-adherent cell present in the B-cell-enriched macrophage-depleted fraction. Pregnant spleen cells cultured in vitro were shown to secrete a soluble suppressive factor(s) into the supernatant medium.

Animals↗
PubMed1979

Differences in the susceptibility of MHC and non-MHC mixed lymphocyte reactions to suppression by murine amnionic fluid and its components.

The ability of mouse amniotic fluid (MAF), alpha-foetoprotein (AFP) and MAF depleted of AFP (MAF - AFP) to suppress primary one-way MLR's was investigated. It was found that MAF, AFP and MAF - AFP were all suppressive of MLR's specific for MHC, K, D or I + S determinants. Suppression was observed when either lymph node or spleen cells were used as the responder cells. Nylon wool column passage of these cells did not significantly affect the immunosuppressive action of these substances. In contrast, MLR's specific for non-MHC/M-locus determinants demonstrated either diminished suppression or augmentation of the response, compared with the MHC stimulated MLR's. Our results show a differential effect of whole MAF and its fractions on the proliferative responses induced by various allogeneic stimuli and suggest that suppression is not due to a non-specific effect on proliferation regardless of the stimulus or cell type involved.

Amniotic Fluid↗
PubMed1979

Quantification of non-specific immunosuppressive factors.

A simple, reproducible and quantitative method for evaluating certain non-specific immunological inhibitors in a variety of biological fluids is described. Human lymphocytes were stimulated with PHA in the presence of colchicine. Phytohaemagglutinin stimulated a large percentage of cells and colchicine's selective blockage of mitosis limited the stimulated cells to one S phase. These conditions effectively established a maximum amount of DNA synthesis within each culture. Quantification of suppression was then achieved by measuring a decrease from this maximum. The PHA-colchicine assay was successfully used to quantify inhibition by normal plasma, normal mouse sera, mouse neonate sera, murine Ehrlich's and sarcoma I ascitic fluids and an immunoregulatory alpha-globulin peptide preparation. Because of the ability to obtain a specific inhibitory activity for the suppressive factors, this assay was particularly suited for following the isolation of inhibitors during the fractionation of suppressive substances from complex fluids.

Animals↗
PubMed1979

Non-H-2 linked control of low versus high responses of antigen-induced lymph node cell proliferation: possible role for antigen-presenting cells.

Quantitative differences in the magnitude of antigen-induced proliferative responses of sensitized lymph node cells between low (C3H/Anf or C3H/Cr) and high (C3H/Hej or CBA/j) responder H-2k mice have been observed 1 to 2 weeks after in vivo sensitization with antigen (OVA, PPD, and GAT). We have shown that antigen presentation is less effective in the sensitized lymph node cell populations from low responder mice compared with those from high responder mice, suggesting that the number and/or functional status of antigen-presenting cells in the regional lymph nodes may be a key factor in determining the magnitude of antigen-induced proliferative responses. These data are consistent with the hypothesis that cell traffic after sensitization plays an important role in determining the immune responsiveness of lymph nodes.

Animals↗
PubMed1979

Inhibition of antigen-induced lymph node cell proliferation by murine amniotic fluid and its components.

Murine amniotic fluid (MAF), alpha-foeto-protein (AFP) and MAF depleted of AFP by affinity chromatography (MAF-AFP) inhibited the T-cell dependent in vitro proliferative responses of lymph node cells sensitized to a variety of soluble antigens. Variable degrees of inhibition were observed with the different antigens used in the assay. In general, the higher the proliferative response induced by a particular antigen, the less it was inhibited by the three inhibitors. Enhancement of proliferation was not infrequently observed at lower concentrations followed by a dose-dependent inhibition as the concentration of the inhibitor was increased. Usually the order of inhibition was MAF greater than MAF-AFP greater than or equal to AFP although variations in inhibitory potency were noted between different preparations of AFP and MAF-AFP. The existence of inhibitors in preparations of MAF depleted of AFP raised the question as to whether MAF contains single or multiple inhibitory factors. The most facile explanation is that two inhbitors exist; AFP and the as yet uncharacterized non-AFP suppressor present in MAF-AFP.

Amniotic Fluid↗
PubMed1978

Studies on extracellular proteases of Streptococcus sanguis. Purification and characterization of a human IgA1 specific protease.

Extracellular caseinolytic activity was found in the culture fluid of Streptococcus sanguis ATCC 10556 grown in a dialyzed culture medium. This activity was due to multiple proteases that differed in their elution from hydroxyapatite, sensitivity to enzyme inhibitors, specificity and optimum pH. IgA protease, which splits human immunoglobulin A1 into intact Fc and Fab could be effectively separated from these relatively non-specific proteases and purified to apparent homogeneity in 20% yield by a five-step procedure. Although the bulk of the dextran sucrase activity was separated from the IgA protease, a small amount of sucrase activity remained with the final IgA protease preparation. In polyacrylamide gel electrophoresis at pH 9.5 both activities were located in the single protein band detected in this preparation. A quantitative method for the assay of IgA protease was developed, based on radial immunodiffusion to quantitate the Fab produced. This was used to follow the specific activity and yield during purification, and to characterize some of the catalytic properties of the enzyme. At an enzyme/substrate ratio of 1: 400 (w/w) the protease could effect 50% proteolysis of IgA in overnight incubation at 37 degrees C. The optimum activity was at pH 8.0, and 50% inhibition was achieved at 4 . 10(-4) M o-phenanthroline or 8 . 10(-4) M ethylene diamine tetraacetate. Concentrations of diisopropyl phosphofluoridate, phenylmethyl-sulfonyl fluoride, iodoacetate and p-chloromercuribenzoate up to 10(-2) M were without effect on the IgA protease activity. Full reactivation of the chelator inhibited enzyme could be achieved by the addition of Mg2+, Mn2+ or Ca2+.

Edetic Acid↗
PubMed1977

Separation of epidermis from dermis with sodium thiocyanate.

After human skin is treated with 2 N sodium thiocyanate, epidermis is easily separated from dermis. The level of cleavage occurs at the lamina lucida of the basement membrane zone. Bullous pemphigoid antigen remains attached to the epidermis.

Histological Techniques↗
PubMed1977

Structure and function of alpha-fetoprotein.

AFP is one of several oncofetal proteins synthesized in large amounts by the fetus. Although synthesis drops markedly shortly after birth, small amounts of AFP continue to be produced in the adult. The function of AFP is unknown, but recent studies suggest the possibility that it may have immunoregulatory properties and/or may influence cell proliferation and growth. The high affinity of AFP for estrogen could have important biological functions, although the significance of this binding has not yet been clearly defined. Elevated levels of AFP are seen in a variety of clinical situations, including pregnancy; hepatic disorders, especially chronic hepatitis; and various malignancies, particularly hepatomas, teratomas, and those of primitive gut origin. It is also produced in murine GVH reactions and in lymphomas, both in mice and humans. In human and murine lymphomas, and murine GVH reactions, the presence of AFP-positive cells and immune suppression are highly correlated, but the role of these in the pathogenesis of the diseases is as yet unclear. It appears, however, that AFP may be produced locally in lymphoid tissues involved in GVH and lymphomatous disease without elevations in serum AFP levels. It is speculated that the local production of AFP in these situations may result from blastogenesis of lymphoid cells directed against foreign tumor or viral antigens. AFP could promote the development of tumors either by suppressing immune surveillance and/or immunity to oncogenic viruses, although this is speculative. Finally, the AFP elevations in maternal serum and amniotic fluid are valuable diagnostically in the detection of fetal abnormalities, particularly neural-tube defects.

Amino Acids↗