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Biomedical subjects

M M Mayer

Publications and source records attributed to M M Mayer.

At least 55 records · Page 3Linked to original sources
PubMed1976

Separation of lymphocyte mitogen from lymphotoxin and experiments on the production of lymphotoxin by lymphoid cells stimulated with the partially purified mitogen: a possible amplification mechanism of cellular immunity and allergy.

A mitogenic factor (MF) from guinea pig lymph node cells (LNC), which was produced by stimulating immune LNC with the specific antigen, ovalbumin, was partially purified by the sequential use of Sephadex G-200 gel filtration. CM-cellulose ion exchange chromatography, DEAE-cellulose ion exchange chromatography, and polyacrylamide disc gel electrophoresis. The product was purified at least 100-fold with regard to protein content. In addition, the purified MF was functionally pure with respect to the absence fo lymphotoxin (LT), another guinea pig lymphokine.

Animals↗
PubMed1976

A new activity of complement component C3: cell-bound C3b potentiates lysis of erythrocytes by C5b,6 and terminal components.

EAC4b,3b (sheep erythrocytes carrying rabbit antibody and guinea pig complement component fragments C4b and C3) adsorb human C5b,6 reversibly; the avidity of binding varies inversely with ionic strength. We believe that the receptor of C5b,6 is contributed by the cell-bound C3b because the binding capacity of EAC4b,3b varies with C3b multiplicity and can be blocked with rabbit antibody to guinea pig C3. The fixation of C5b,6 to the erythrocyte-bound C3b serves to concentrate C5b,6 on the cell surface; as a consequence, the hemolytic efficiency of C5b,6 is almost 100 times greater when assayed with EAC4b,3b than with plain erythrocytes. This potentiation represents a hitherto unrecognized function of cell-bound C3b.

Animals↗
PubMed1975

On the mechanism of cytolysis by complement: evidence on insertion of C5b and C7 subunits of the C5b,6,7 complex into phospholipid bilayers of erythrocyte membranes.

The doughnut hypothesis of cytolysis by complement [Mayer, M. M. (1972) Proc. Nat. Acad. Sci. USA 69, 2954-2958] describes an annular structure made up of C5b-9 (complement factors C5b, C6, C7, C8, and C9) which becomes inserted in the lipid bilayer of the cell membrane, thus creating a hole. We now present initial explorations of this hypothesis. EAC1-6 and EAC1-7 (sheep erythrocytes carrying rabbit antibody and complement factors C1 through C6 or C1 through C7, respectively), prepared with either 125I-C3 or 125I-C5 were incubated with trypsin and the release of bound 125I was measured. In the case of 125I-C3, all of the radioactivity was released by trypsin from both intermediates. With 125I-C5, trypsin released all of the 125I from EAC1-6, but only 40-55% from EAC1-7. Possible reasons for resistance of the C5b subunit in EAC1-7 to tryptic digestion are discussed; in terms of the doughnut hypothesis it would be due to shielding by lipid molecules as a consequence of insertion into the lipid bilayer. In accord with this interpretation we have also found that C5b in EAC1-7, but not in EAC1-6, resists elution by 0.3 M NaC1. Similarly, we have found that 125I-C7 in EAC1-7 resists stripping by trypsin. Hence, we now propose the hypothesis that hydrophobic polypeptide chains from the C5b and the C7 subunits of C5b,6,7 complex become inserted in the phospholipid bilayer and that subsequent reactions with C8 and C9 open a channel across the membrane.

Animals↗
PubMed1975

Studies on lymphokines: the production of antibody to guinea pig lymphotoxin and its use to distinguish lymphotoxin from migration inhibitory factor and mitogenic factor.

Guinea pig lymphotoxin, which was produced by stimulating immune lymph node cells with the specific antigen, ovalbumin, was partially purified by the sequential use of Pevikon block electrophoresis, ion exchange chromatography on DEAE-cellulose, and polyacrylamide disc gel electrophoresis. The lymphotoxin recovered from the final step was purified approximately 200- to 300-fold as compared to the starting material, but nevertheless contained at least one major contaminant protein. Rabbits were immunized with the partially purified lymphotoxin, and an antiserum capable of neutralizing the cytotoxic effect of lymphotoxin was obtained. The anti-lymphotoxin activity was shown to be due predominantly to IgM immunoglobulin. The antiserum neutralized concanavalin A-induced lymphotoxin with equal efficiency as antigen-induced lymphotoxin. On the other hand, the anti-lymphotoxin serum did not neutralize preformed mitogenic factor or migration inhibitory factor (MIF) which had been produced by antigen-stimulated immune lymph node cells. Thus these activities appear to be due to substances which are antigenically distinct from lymphotoxin. Likewise, anti-lymphotoxin serum, when present in cultures of antigen-stimulated immune lymphoid cells, caused no diminution in the amount of mitogenic factor or MIF which was produced, indicating that it had no direct deleterious effect on the function of the lymphoid cells responsible for producing these lymphokines.

Animals↗
PubMed1975

The molecular dimensions of mitogenic factor from guinea pig lymph node cells.

The molecular dimensions of a mitogenic factor from guinea pig lymph node cells were investigated by means of gel filtration, sucrose density gradient ultracentrifugation, and CsCi isopycnic ultracentrifugation. The mitogenic factor was produced by stimulation of immune lymph node cells from inbred guinea pigs, strain 2 or 13, with the specific antigen, ovalbumin; and mitogenic activity was assayed by measuring incorporation of tritiated thymidine by target lymph node cells from syngeneic animals not immune to ovalbumin. The D-20,w of the mitogenic factor was estimated to be (9.9 plus and minus 0.2) times 10-7 cm2/sec by gel filtration on Sephadex G-100, and the apparent S20,w was estimated to be 2.4 plus and minus 0.2 S by sucrose density gradient ultracentrifugation. The buoyant density was determined to be 1.324 plus and minus 0.006 g/ml by CsCi isopycnic ultracentrifugation, and from this value the partial specific volume of mitogenic factor was estimated to be 0.71. From these data the molecular weight of the mitogenic factor was calculated to be 20,000, and the frictional ratio was calculated to be 1.2.

Animals↗
PubMed1972

Mechanism of cytolysis by complement.

The attack of complement is directed against the lipid moiety of the cell membrane; a single lesion at the site of fixation of complement proteins C5-C9 is responsible for lysis of a cell. There are two hypothetical models for the generation of this membrane lesion. The first of these, designated the leaky-patch model, postulates either direct enzymatic attack or enzymatic generation of a lytic substance by C5-C9. As a result, the phospholipid bilayer of the membrane would be disrupted and a leaky patch permitting passage of water and salt would appear. However, this hole would persist only as long as enzymatic action continues. Thus, the leaky-patch model would not produce a stable hole, and for this reason it is considered an unlikely mechanism. The second hypothesis, termed the doughnut model, describes a structural concept for creating a hydrophilic passage through the hydrophobic phospholipid bilayer of the membrane. In essence, this would be a rigid and hollow structure, like a doughnut, with a hydrophobic exterior, which is inserted into the phospholipid bilayer of the cell membrane in such a way that its hollow hydrophilic core becomes a channel through which salt and water can exchange freely between the interior of the cell and the extracellular environment. The late-acting complement proteins C5-C9 are the most probable source of the structural components of the doughnut. A combination of the leaky-patch and doughnut models may represent the most likely mechanism.

Cell Membrane↗
PubMed1971

An alternate complement pathway: C-3 cleaving activity, not due to C4,2a, on endotoxic lipopolysaccharide after treatment with guinea pig serum; relation to properdin.

The reaction between endotoxic lipopolysaccharide (LPS) and the guinea pig complement system was shown to proceed by way of an intermediate complex, LPS-X, which contains at least six guinea pig serum proteins. LPS-X, like [unk] (sheep erythrocytes carrying antibody molecules and [unk] complexes), destroys the C3 molecule by cleavage. On incubation at 37 degrees C, LPS-X loses its capacity to destroy C3 at about the same rate as the decay of [unk], so that it has been assumed that LPS-X carries [unk] sites that are responsible for the destruction of C3. We have now shown that monospecific rabbit antiguinea pig C2, which effectively inhibits C3 cleavage by [unk], does not interfere with the destruction of C3 by LPS-X. Furthermore, not more than a trace of C2a(d) is released from LPS-X on incubation at 37 degrees C. These results indicate that LPS-X does not carry a significant quantity of [unk] and, hence, that its capacity to destroy C3 is due to another factor which is presumably a component of the properdin system.

Animals↗