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Biomedical subjects

J Marbrook

Publications and source records attributed to J Marbrook.

At least 55 records · Page 3Linked to original sources
PubMed1979

Antibody responses of human lymphocytes in vitro. Specificity and physical properties of plaque-forming cell precursors.

When human tonsillar lymphocytes are cultured with pokeweed mitogen they generate a larger number of antibody-secreting cells. A substantial number of the plaque-forming cells generated have specificity for sheep erythrocytes but very few are specific for either bovine or horse erythrocytes. We have investigated the physical properties of sheep erythrocyte-specific precursors and have found that they have the characteristics of larger lymphocytes and are heterogeneous with respect to density. Our results support the concept that the percursors which can be induced by pokeweed mitogen to develop into plaque-forming cells belong to a pre-activated sub-population of lymphocytes.

Animals↗
PubMed1979

Antibody responses of human lymphocytes in vitro. Enhancing effects of hydrocortisone.

Cultures of human tonsillar lymphocytes stimulated by pokeweed mitogen in the presence of hydrocortisone succinate generate more sheep red blood cell-specific plaque-forming cells than when the hydrocortisone is absent. Such enhancement is even more marked when sheep red blood cells and pokeweed mitogen are present in cultures. This contrasts with the inability of sheep red blood cells to enhance pokeweed mitogen-stimulated response in cultures lacking hydrocortisone. Hydrocortisone causes greater enhancement when the concentration of cells in culture is high than when it is low. These data are consistent with hydrocortisone inhibiting the activity of suppressor cells which would otherwise mask helper effects.

Animals↗
PubMed1978

The frequency of clones of cytotoxic lymphocytes generated by H-2 antigens.

By using a culture system that allows the segregation of individual precursors of cytotoxic lymphocytes, the number of clones generated by cells from different combinations of congenic mice have been measured. It has been found that 0.3% of the total anti-H2d clones are generated by stimulators which differ predominantly at the H-2 locus. The contribution of non-H-2 antigens to anti-H-2 responses is discussed.

Animals↗
PubMed1978

Splenic foci of cytotoxic lymphocytes in a graft-versus-host reaction.

It has been established that cytotoxic lymphocytes are generated in discrete foci in the spleens of mice undergoing a graft-versus-host reaction. The foci segregated randomly in such spleens. 2.8 X 10(4) lymph node cells, 2.3 X 10(5) spleen cells and 2.7 X 10(6) thymus cells from CBA mice generated a mean of one focus in lethally irradiated (CBA X DBA)F1 recipient mice. Cytotoxic foci were detected when cytotoxicity was measured by two different cytotoxicity assays, the release of [51Cr]-sodium chromate from [51Cr]-labelled target cells and colony inhibition. The seeding efficiency of cytotoxic focus-forming cells has been estimated at 19%.

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PubMed1977

Interferon-induced antibody suppression: a selective effect on high density, late responding precursor cells.

Mouse spleen cells have been fractionated into three subpopulations by density gradient centrifugation and the effect of interferon on the ability of each fraction to generate an antibody response in vitro has been examined. The results show that only the antibody-forming cell precursors (AFCP) of the high density, late responding fraction are suppressed by interferon. The presence of interferon had no effect on either the number or the mean size of clones of antibody-forming cells in cultures of the low and medium density fractions. Interferon-mediated suppression of the response of high density precursors was due to a decrease in the number but not the size of responding clones. These results suggest that interferon suppresses antibody responses by affecting the degree to which high density AFCP can becoming activated rather than the degree to which precursors proliferate.

Animals↗
PubMed1977

Clones of cytotoxic lymphocytes in culture: the difference in specificity between stimulated and nonstimulated cytotoxic lymphocytes.

The specificity of individual clones of cytotoxic lymphocytes (CL) which develop upon stimulation by semi-allogeneic cells, have been examined and compared with the specificity of CL clones which develop spontaneously when normal spleen cells are cultured without stimulator cells. It was found that the specificity of stimulated clones was different from the specificity of 'spontaneous' clones. Specifically stimulated clones from CBA cells cultured with (CBA x DBA)F1 stimulator cells, did not discriminate between the H2dP815 and H2dDBA splenic blast, and lysed both targets. In contrast, spontaneous CL clones from cultures of CBA or (CBA x DBA)F1 spleen cells were found to lyse either P815 or DBA blast, but not both. The results indicated that the spontaneous CL clones were not a representative sample of the the total pool of CL.

Animals↗
PubMed1977

Spontaneous clones of cytotoxic T cells in culture. III. Discriminatory lysis of pairs of syngeneic blast induced by different mitogens.

When normal spleen cells are cultured for 4 days in polyacrylamide vessels, individual clones of cytotoxic lymphocytes (CL) can be detected. The specificity of these 'spontaneous' CL was investigated by assaying the cytotoxic acitivity of cells from individual clones against pairs of different target. Target cells used were syngeneic blast cells induced by dextran sulfate, lipopolysaccharide (LPS), concanavalin A (ConA) and phytohemagglutin (PHA). It was found that LPS blasts were lysed by a separate set of CL clones from those which lysed PHA blasts of the same H-2 haplotype, and the clones of CL which lysed PHA blasts were a subset of all the clones which lysed ConA blasts. When individual clones of spontaneous CL were assayed against LPS and DS blasts, there were clones which lysed both types of blasts as well as clones which were specific for either LPS or DS blasts. These results have been interpreted as demonstrating that spontaneous CL can recognize and kill subsets of cells which are stimulated by different mitogens.

Animals↗
PubMed1976

An estimation of the frequency of precursor cells which generate cytotoxic lymphocytes.

The cell-mediated immune response has been generated in vitro with a polyacrylamide culture system which allows the segregation of foci (clones?) of cytotoxic lymphocytes. Using the method of limiting dilutions, the frequency of precursor cells in CBA spleen cells able to generate a cytotoxic response against DBA mastocytoma is estimated at 1 per 1,700 cells.

Animals↗
PubMed1976

Immune conservation: a possible consequence of the mechanism of interferon-induced antibody suppression.

The effect of interferon preparations on the development of single clones of antibody-forming cells generated against sheep red blood cells in mouse spleen cell cultures has been studied. It was found that the presence of interferon had no effect on either the number or the size of clones which developed early in the in vitro antibody response. At the peak of the response (day 3), a decrease in the number but not in the size of clones was observed in interferon-treated compared to control cultures, while by day 4 both the size and number of clones were significantly decreased. These findings indicate that interferon appears to affect only nonactivated B cell precursors by preventing them from becoming activated and commencing clonal expansion. Early responding precursors, which are in cell cycle, presumably having been previously activated in vivo, are refractory to interferon-induced suppression in vitro. The way in which this immunosuppressive activity of interferon might be of great advantage to an animal as a means of "immune conservation" during viral infections is discussed.

Animals↗
PubMed1976

The surface morphology and the cell cycle of mastocytoma target cells: no apparent effect on cell-mediated killing.

Mastocytoma cells (P-185) have been separated by velocity sedimentation into fractions which were highly enriched for cells at discrete stages of the cell cycle. By scanning electron microscopy it was shown that the surface morphology of the majority of cells in each fraction was characteristic of that fraction. No difference could be detected between isolated fractions and unfractionated cells in their ability to be lysed by cytotoxic lymphocytes.

Animals↗
PubMed1976

Modulating effects of interferon preparations on an antibody response in vitro.

The effect of mouse interferon preparations on the primary in vitro antibody response of mouse spleen cells was studied. Concentrations of interferon greater than 8 units per ml significantly inhibited the antibody response while low concentrations of 0-08-0-8 units per ml could be shown to be mildly enhancing. Various treatments which affected the antiviral activity of the interferon preparations reduced the immunosuppressive activity to a similar extent. Interferon acts during the first few hours of a response but the effect is not apparent for at least 50 h. Interferon had no effect when added after 48 h. The kinetic data has been interpreted as demonstrating interferon-sensitive and interferon-resistant components of the in vitro response. The results from investigations of the polyclonal response to lipopolysaccharide support the view that interferon acts mainly on B cells alone, although effects on T-B interactions cannot be excluded.

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