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Biomedical subjects

A Coutinho

Publications and source records attributed to A Coutinho.

At least 307 records · Page 17Linked to original sources
PubMed1978

Shared antigenic determinants by mitogen receptors and antibody molecules to the same thymus-independent antigen.

The antibody response to dextran B1355 is thymus independent, and in high responder mice, over 90% of the antibodies carry the idiotype of an alpha-1,3 binding myeloma protein (J558). The present experiments demonstrate: (a) dextran B1355 is a B-cell mitogen both in a strain which carries the J558 idiotype on antibodies and in a low-responder strain which does not express that idiotype on antibodies to dextran; (b) anti-idiotypic antibodies to J558 recognize a dextran-specific surface receptor on 10--15% of all splenic B cells in those two strains as well as in all strains so far tested; (c) as shown by inhibition experiments such surface receptors cross-react with J558, and (d) anti-idiotypic antibodies are mitogenic for spleen cells of both strains resulting in B-cell proliferation and maturation to polyclonal antibody secretion.

Antibodies↗
PubMed1978

The switch from IgM to IgG secretion in single mitogen-stimulated B-cell clones.

The frequency of mitogen-reactive B cells yielding an IgG plaque-forming cell (PFC) response has been determined in vitro by limiting dilution analysis under culture conditions which allow every growth-induced B cell to grow and mature into a clone of Ig-secreting cells. The frequencies of lipopolysaccharide (LPS)-and lipoprotein-reactive precursors for IgG-secreting cells in the spleen of 6--8 wk old C3H/Tif and of C57BL/67 mice were found to be between 1 in 30 and 1 in 40 B cells and, therefore, only one tenth of the frequencies of mitogen-reactive precursors of clones secreting IgM. All IgG-secreting cells developed by switching in clones which previously contained IgM-secreting cells. This was shown in two experiments where the total number of mitogen-reactive precursor yielding IgM-secreting cell clones was limited such that 82 or 90% of all responding cultures originated from one precursor. Thus, of 480 cultures in the first and 720 cultures in the second experiment, 86 and 98 cultures were found positive, yielding IgM-secreting cells at day 5. When the same cultures were assayed at day 7 for IgG-secreting cells 9 and 10 cultures were found positive. All 19 cultures with IgG-secreting cells previously had contained IgM-secreting cells. The probability that IgG-secreting cells and IgM-secreting cells would have arisen from independent precursors can be calculated using Fisher's exact test of independence. For the two experiments those probabilities are 3.4 X 10(-7) and 4.0 X 10(-9). Since we have previously shown that each cell in a mitogen-stimulated, growing B-cell clone divides, and that each dividing cell secretes Ig, we conclude from these experiments that the large majority--in our experiments all--of the IgG-secreting cells in mitogen-stimulated B-cell clones develop by switch from IgM-secreting cells. IgG-secreting cells develop either early or late during growth of a single IgM-secreting cell clone. The switch to IgG secretion, therefore, is not fixed in the time of clonal growth after mitogenic stimulation.

Animals↗
PubMed1978

An antiserum which recognizes lipopolysaccharide-reactive B cells in the mouse.

Rabbit antisera have been prepared against spleen B cells from C3H/Tif mice, high responders to lipopolysaccharide (LPS). After complete absorption on tissues of C3H/Hej mice (LPS nonresponders), such antisera specifically stain and kill (in the presence of complement) a fraction of the B cells from a number of LPS high responder strains, and fail to recognize any cells in two different LPS nonresponder strains, C3H/HeJ and C57B1/10.Sc.Cr. The ontogeny, organ and strain distribution of this B cell marker parallels LPS reactivity. Frequencies of cells stained by this antiserum correspond to the frequencies of LPS-reactive B cell precursors recently determined. This antigent(s) is expressed by LPS-activated B cell blasts but not by cells which remain small after 48 h in the presence of LPS. Removal of the cells recognized by the antisera leads to depletion of LPS-reactive cells, while enriching for reactivity to another B cell mitogen, e.g. lipoprotein.

Animals↗
PubMed1978

Genetic and functional characterization of an antiserum to the lipid A-specific triggering receptor on murine B lymphocytes.

The inheritance of responsiveness to lipopolysaccharide (LPS), and of a marker recognized in LPS-reactive cells by a heterologous antiserum, was studied in crosses between C3H/HeJ (nonresponder) and C3H/Tif (high responder) mice. F1 hybrid mice show codominant expression of these traits: (a) LPS-reactive cells are only hlaf as frequent in the hybrids as in the high responder parent; (b) the serologically defined marker is expressed in half as many cells in the hybrids as in the high responder parent. In backcross generations, both LPS responsiveness and this serological marker segregated into high, intermediate, and nonresponders. LPS or free lipid A, but not two other B cell mitogens (lipoprotein, and purified protein derivative of tuberculin), compete with the antiserum for binding to the B cell surface membrane, and are capable of completely inhibiting such binding without interfering with the binding of a-ti-Ig antibodies or complexes to Fc receptors. The addition of an IgG fraction of the antiserum to B cell cultures results in exponetial growth of the cells and in maturation to antibody secretion. This mitogenic activity is dose-depedent and absorbable on spleen cells from LPS high responder mice. Taken together, these observations suggest that this antiserum contains antibodies to the lipid A-specific triggering receptor on B lymphocytes.

Animals↗
PubMed1977

Absolute frequencies of lipopolysaccharide-reactive B cells producing A5A idiotype in unprimed, streptococcal A carbohydrate-primed, anti-A5A idiotype-sensitized and anti-A5A idiotype-suppressed A/J mice.

The absolute frequencies of B cells-producing A5A idiotype have been determined in vitro by limiting dilution analysis in a culture system in which every LPS-reactive B cell grows into a clone of IgM-secreting cells. Spleen cells from normal A/J mice contain 1 A5A-idiotype-producing B-cell precursor in 2.5 X 10(3) LPS-reactive B cells. Approximately a 10-20-fold increase in frequencies of precursor cells from antigen priming with Strep A-CHO (1 in 2.8 X 10(2)) or from sensitization with IgG1 anti-A5A idiotype (1 in 1.3 X 10(2)). Injection of IgG2 anti-A5A idiotype which has been shown to suppress A5A idiotype in vivo results in only a marginal and maybe insignificant decrease in precursor frequencies (1 in 6.7 X 10(3)). On the other hand, priming does not result in a detectable qualitative difference in the specific precursor cells, since each clone of B cells secretes 30 ng of A5A-bearing Ig within 8 days of culture, regardless of being unprimed or primed. Nearly half of all A5A idiotype-producing clones, both from unprimed as well as from primed mice, show antigen specificity in binding A-CHO. Priming by antigen, therefore, also results in a 10-fold increase in the frequency of idiotype positive B cells without antigen specificity. This result is a prediction of the network hypothesis.

Animals↗
PubMed1977

Frequencies of mitogen-reactive B cells in the mouse. I. Distribution in different lymphoid organs from different inbred strains of mice at different ages.

Frequencies of mitogen-reactive B cells have been determined in vitro under culture conditions which allow every growth-inducible B cell to grow and mature into a clone of Ig-secreting PFC. The frequencies of LPS-reactive B cells in the spleen of 6- to 8-wk old mice were between 1 in 3 and 1 in 10 splenic B cells from the following inbred strains of mice: C3H/Tif; BALB/c; BALB/c nu/nu; C57BL/6J; DBA/2J; C57BL/6J x DBA/(2J)F(1); and CBA and A/J. Very similar frequencies are found for lipoprotein-reactive B cells in BALB/c, BALB/c nu/nu, C3H/Tif, and C3H/HeJ mice. No LPS-reactive cells but normal frequencies of lipoprotein-reactive cells were found in C3H/HeJ mice, genetically nonreactive to LPS. SJL mice had significantly lower frequencies of LPS- and of lipoprotein-reactive B cells (1 in approximately 30 B cells). The number of LPS- and of lipoprotein-reactive B cells in spleen was dependent upon the age of the mouse. Newborn spleen contained approximately 10 percent of the number of reactive cells found at 6- to 8-wk of age. From there the frequencies declined again to drop below 5 percent of the maximal number at ages beyond 11 mo. LPS-reactive B cells yielding IgM- and IgG-PFC responses could be found in mesenteric lymph nodes, bone marrow, thymus, thoracic duct, and peripheral blood of 6- to 8-wk old mice. Their frequencies were one in three to five lymph node cells, 1 in 50 to 100 bone marrow cells, one in 10(5) thymus cells, and 1 in 20 to 40 thoracic duct or peripheral blood cells.

Aging↗
PubMed1977

Frequencies of mitogen-reactive B cells in the mouse. II. Frequencies of B cells producing antibodies which lyse sheep or horse erythrocytes, and trinitrophenylated or nitroiodophenylated sheep erythrocytes.

The B-cell mitogens LPS and lipoprotein stimulate 20-35 percent of all B cells in the spleen of 6- to 8-wk old C3H/Tif mice, as determined by limiting dilution analysis of precursors. Each reactive cell grows to a clone of IgM-secreting PFC, enumerated in a hemolytic plaque assay detecting all IgM secreting cells, regardless of v-region specificity. We have used these mitogens to reveal the total repertoire of Ig specificities produced by these mitogen-reactive B cells. We have determined in plaque assays with six different target erythrocytes the number of spleen cells limiting to one the number of mitogen-reactive B cells detected as specific IgM-secreting clones in each of these plaque assays. By this method, the absolute frequencies of precursor B cells with defined v-gene specificities could be calculated, for at least, one third of all B cells. The frequencies of specific IgM-plaque-forming B-cell clones within the total pool of mitogen-reactive B cells was 1 in 10 for NIP(12),-SRC, 1 in 50 for TNP(12)- SRC, 1 in 100 for NIP(1)-SRC, 1 in 160 for TNP(3)- SRC, 1 in 500 for HRC, and 1 in 1,000 for SRC. These frequencies were the same in the LPS- and in the lipoprotein-reactive B-cell population for TNP(30)- SRC and SRC.

Animals↗
PubMed1977

T cells which proliferate in response to concanavalin A include cells which proliferate in mixed leucocyte reactions.

Selection in long-term culture of alloreactive T cells, by successive in vitro restimulation with semi-allogeneic cells, results in primed responder cell populations which maintain full proliferative reactivity to allogeneic cells as well as to the T cell mitogens concanavalin A (Con A) and phytohemagglutinin (PHA) but are depleted of cells which can effect target cell destruction in either a specific or nonspecific manner. Con A-induced T cell blasts (selected by velocity sedimentation) can revert to small resting lymphocytes in the presence of inert "filler" cells. Con A blasts which have reverted, readily proliferate in response to Con A or allogeneic stimulator cells but are largely depleted of effector killer cells and PHA-responsive cells.

Animals↗
PubMed1977

Derivation of hybrids between a thymoma line and spleen cells activated in a mixed leukocyte reaction.

We have established 16 independent hybrid lines derived from a fusion between an AKR thymoma and mixed leukocyte reaction-stimulated C57BL/6 spleen cells. The hybrids express both parental H-2 alleles and show hybrid glucose-6-phosphate isomerase activity. Two of the lines showed Fc receptor activity not expressed in the parental thymoma. The AKR Thy-1.1 allele was expressed in all hybrid lines, but no Thy-1.2 could be detected. No killing activity was retained in the hybrid cells, probably because Sendai virus-mediated fusion of killer cells resulted in the lysis of the thymoma fusion partner.

Animals↗
PubMed1977

Clonal growth and maturation to immunoglobulin secretion in vitro of every growth-inducible B lymphocyte.

The frequency of normal murine B lymphocytes initiating growth in diluted suspension cultures in the presence of a B cell mitogen, such as lipopolysaccharide, can be increased approximately 10(4) fold by the addition of 2 X 10(6) normal thymus cells per ml. This increase in the frequency of growing cells by thymus cells can also be observed with X63-AG8 myeloma tumor cells secreting IgG1. Thus thymus cells may not contribute growth-stimulating factors, but may supply growth-supporting factors. Culture medium and plastic dishes can be conditioned by preincubation with thymus cells for a day after which the thymus cells may be omitted from further culture for maximal B cell growth. Irradiation of thymus cell abolishes their growth-enhancing properties. Thymus cells can be syngeneic and allogeneic with the growing B cells. The frequency of growing LPS-reactive, normal B cells in spleen of 6-8 week old C3H/Tif mice was determined by limiting dilution analysis to be one of three splenic B cells. With this limiting dilution analysis, it was also shown that the cloning efficiency of XB3-AG8 myeloma tumor cells in suspension culture in the presence of thymus cells is practically 100%. Analysis of the growth kinetics of single clones of LPS-reactive, normal B cells shown that these B cells divide every 18 hr. Within the first 126 hr of growth, every B cell in the clone divides, and every dividing B cell in this clone secretes sufficient immonoglobulin to form a hemolytic plaque. The conditions of in vitro suspension cultures of murine B lymphocytes are therefore perfect to the extent that every B cell capable of growth will grow as a single clone.

B-Lymphocytes↗
PubMed1977

Regulation of in vitro immunocyte activation: origin of and targets for cell-released inhibitors.

Supernatants from incubated normal mouse spleen cells suppressed the DNA synthetic response induced by polyclonal B- and T-cell activators and the primary immune response to sheep erythrocytes in normal spleen cells in vitro. The inhibitory effects of the supernatants were found to be dependent on the culture system used. The main cell population producing or releasing the inhibitory factors was nonadherent spleen cells, but macrophages and bone marrow cells could also give supernatants with inhibitory effects. Thymocytes did not release any inhibitors under the same conditions. Separation of the supernatants showed that there were at least two factors with inhibitory effects on proliferation in lymphocytes. One of these factors had a molecular weight of less than 10,000 (not degradable by protease) and suppressed activation by all tested polyclonal B- and T-cell activators. Another factor (a protein with a molecular weight of more than 30,000) inhibited activation by some polyclonal B-cell activators (lipopolysaccharide, type III pneumococcal polysaccharide) whereas the proliferation induced by dextran sulfate was less or not at all affected under the same culture conditions. Trivial mechanisms for inhibition by supernatant factors, such as medium depletion, general toxicity, and accumulation of free thymidine in the medium, were excluded.

Animals↗
PubMed1977

Independent segregation of two functional markers expressed on the same B-cell subset in the mouse: the Mls determinants and LPS receptors.

Mice of the C3H/Tif strain display a mixed leukocyte reaction (MLR) with all H-2k strains carrying any of the known alleles of the Mls locus. In particular, C3H/Tif is incompatible with the related substrain C3H/HeJ, from which it also differs at the locus responsible for the recognition of lipopolysaccharides (LPS) as B-cell mitogens, and at the Mod-1 locus. Our genetic analysis indicates that the MLR incompatibility between these strains is not H-2-linked and segregates as controlled by a single locus, most probably identical to Mls, for which the C3H/Tif strain expresses a previously unidentified allele, Mlse. Moreover, segregation data show that this locus assorts independently of LPS responsiveness and that neither marker is closely linked to the Mod-1 locus in linkage group II.

Alleles↗