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At least 19 recordsLinked to original sources
PubMed1977

Characterization of guinea pig mitogenic factors. I. Evidence that antigen-induced mitogenic factor and mitogenic factor from mixed leukocyte cultures are distinct molecular entities.

Mitogenic factor from BCG-sensitized cells stimulated with antigen (PPD) was found to have a m.w. between 20 and 25,000 daltons and an isoelectric point of about 7.5. The blastogenic activity of this factor was not affected by L-fucose or heating at 56 degrees C for up to 1 hr. Mitogenic factor obtained from supernatants of allogeneic cell mixtures (MLC-MF) on the other hand, had a m.w. at 15 to 18,000 daltons and an isoelectric point of 6.5. The blastogenic activity of MLC-MF was inhibited by 0.1 M L-fucose. The factor was stable at 56 degrees C for 1 hr. An antibody prepared against MLC-MF inhibited the MLC reaction as well as the activity of MLC-MF on non-committed cells. This antibody, however, did not affect the response of lymphocytes to PHA or PPD and had no suppressive effect on PPD-MF. The antibody was not cytotoxic and its suppressive activity in the MLC response could not be absorbed out by lymphoid cells indicating that it is probably directed against a lymphocyte activation product (MLC-MF) rather than membrane antigens. The chemical and immunologic differences exhibited by PPD-MF and MLC-MF indicate that these two lymphokines are distinct molecular entities.

Animals↗
PubMed1979

Mitogen-activated B-cell blasts reactive to more than one mitogen.

One of three splenic B cells of 2- to 3-mo-old C57BL/6J or C3H/Tif mice are activated either by lipopolysaccharide (LPS) or by lipoprotein (LP) to grow and to mature to IgM-secreting cells. When mitogen-activated blast cells, after a 2-d activation period, are separated from nonactivated, small cells by velocity sedimentation, and no mitogen is readded, the blasts do not continue to grow but do continue to secrete IgM for several days. When the homologous mitogen is added for restimulation, the blast cells continue for several days to divide every 18 h and to develop IgM-secreting, plaque-forming cells. Frequency analyses at limiting dilutions of reactive B-blasts show that one cell in approximately equal to 1.2--1.5 blasts continue to grow and mature in the presence of the homologous mitogen, either LPS or LP. When the B-cell blasts obtained in a first activation period with either LPS or LP are restimulated with a heterologous mitogen, LPS, LP, Nocardia mitogen or mitogens contained in fetal calf serum a high proportion of the blasts continue to grow and mature to IgM-secreting cells. Frequency analyses show for LPS- or LP-blasts, restimulated in a heterologous fashion with either LP or LPS, that one cell in 1.35--1.5 blasts continue to divide and to mature to IgM-secreting cells. C3H/HeJ-splenic B-cells, which are LPS nonresponders, can only be activated to blast cells by LP. These LP-activated blasts can be restimulated by the homologous LP and by Nocardia mitogen and mitogens of fetal calf serum, but not by LPS. The results indicate that the majority of splenic B cells of 2- to 3-mo-old C57BL/6J or C3H/Tif mice are reactive to more than one B-cell mitogen. B cells, therefore, can possess in their surface membrane multireactive mitogen-receptor complexes which regulate growth and maturation.

Animals↗
PubMed1978

Mitogen induction of murine C-type viruses. IV. Effects of lipoprotein E. coli, pokeweed mitogen and dextran sulphate.

Lipoprotein E. coli, a B-cell mitogen, is identified as a new agent inducing the release of endogenous C-type virus from mouse spleen cells. Like lipopolysaccharide, a previously identified inducer, this compound has a synergistic effect with 5-bromo-2'-deoxyuridine. Induced virus has the characteristic density as well as morphology of C-type viruses. Budding viruses are detected on cultured BALB/c cells by electron microscopy 2 to 4 days following culturing in the presence of lipoprotein. Pokeweed mitogen, a compound mitogenic for T- and B-cells was negative when tested for virus induction, both alone and in combination with 5-bromo-2'-deoxyuridine. Dextran sulphate, another B-cell mitogen, was negative for induction as well. However, when, combined with lipopolysaccharide, it enhanced the virus release induced by this mitogen. In contrast, no additive effects were observed either by combining dextran sulphate with other virus amplifying mitogens or by combinations of mitogens which both have virus-inducing ability. This finding is discussed with respect to B-cell differentiation.

Animals↗
PubMedDate not supplied

Inhibition and potentiation of T lymphocyte response to mitogens. Studies using two mitogenic stimuli simultaneously.

Rat thymocytes were stimulated with phytohaemagglutinin (PHA), Concanavalin A (Con A), pokeweed mitogen (PWM) and lipopolysaccharide (LPS) or with mixtures of two of these mitogens, added simultaneously to in vitro cultures. Four-five concentrations of first mitogen were matched with four-five concentrations of second mitogen, in all possible combinations. Synergistic effects were observed with LPS plus PHA and LPS plus PWM and inhibitory effects with PHA plus Con A and LPS plus Con A. The hypothesis is discussed that an inhibitory effects occurs when two mitogens react with identical or very similar receptors on the lymphocyte surface, while a synergistic effect is produced by two mitogens reacting with different receptors.

Animals↗
PubMed1979

Mitogenic activity of Mycoplasma pulmonis. II. Studies on the biochemical nature of the mitogenic factor.

The mitogenic activity of Mycoplasma pulmonis has been demonstrated to reside in the membrane of this microorganism. Studies aimed at the identification of the membraneous mitogenic factor have revealed that membrane proteins are essential components of this mitogenic manifestation. In addition, it has been shown that the micro-organism's outer surface membrane proteins are responsible for mitogenic activity. It has been shown, however, that isolated membrane lipids are not mitogenic for rat lymphocytes and are not required for the membrane's mitogenic potential.

Animals↗
PubMed1979

Mitogenic proteins of pokeweed. I. Purification, characterization and mitogenic activity of two proteins from pokeweed (Phytolacca octandra).

Saline extracts from the roots of the pokeweed species. Phytolacca octandra were separated by ion-exchange chromatography into three fractions, Po-1, Po-2 and Po-3. Po-1 contained two monomeric proteins with molecular weights of 36,000 and 29,000 and these were partially purified by gel filtration. Po-2 was purified as a single polymeric protein composed of approximately ten 14,000 mol. wt polypeptides and is a new pokeweed mitogen. Po-3 was purified as a single polymeric protein composed of approximately four 31,000 mol. wt subunits, and apart from its polymeric structure closely resembles commercial pokeweed mitogen (PWM). Po-2 and Po-3 were mitogenic for unseparated human peripheral blood lymphocytes but the degree of mitogenic activity in Po-2 preparations was dependent on storage following purification. Purified B cells were not stimulated by either mitogen. Po-3 was a potent mitogen for T cells but preparations of Po-2 required storage before they stimulated T cells. Higher responses were observed in co-cultures of B and T cells than in separated B and T cell cultures. It is suggested that human B and T lymphocytes show synergy in their responses to Po-2 and Po-3.

Amino Acids↗
PubMed1978

Prostaglandin suppression of mitogen-stimulated lymphocytes in vitro. Changes with mitogen dose and preincubation.

In this study we further characterize the properties of the prostaglandin-producing suppressor cell. Overnight preincubation of peripheral blood mononuclear cells results in an increased response of the cells to phytohemagglutinin or Concanavalin A compared to the response of fresh cells. This increase in mitogen response with preincubation was similar in magnitude to the increase in mitogen response of fresh cells after the addition of indomethacin. The two manipulations were not additive; that is, after preincubation, indomethacin caused much less enhancement of mitogen stimulation of peripheral blood mononuclear cells (100 +/- 12% increase before preincubation vs. 12 +/- 6% after preincubation; mean+/-SEM, P < 0.001). Preincubated cells also lose sensitivity to inhibition by exogenous prostaglandin E(2). It requires the addition of 100- to > 1,000-fold more exogenous PGE(2) to produce comparable inhibition of phytohemagglutinin-stimulated preincubated cells than is required for inhibition of phytohemagglutinin-stimulated fresh cells. The enhancing effect of indomethacin increases with decreasing doses of phytohemagglutinin. Indomethacin causes a 1,059+/-134% increase in [(3)H]thymidine incorporation at the lowest dose of phytohemagglutinin (0.2 mug/ml), and a 4+/-3% increase at the highest dose (20 mug/ml). This increase in response to indomethacin with a lower dose of phytohemagglutinin is due to increased sensitivity to inhibition by PGE(2) at lower mitogen doses. The prostaglandin-producing suppressor cell assay and the short-lived suppressor cell assay measure over-lapping phenomena. The increased suppressive effect of the prostaglandin-producing suppressor at suboptimal mitogen dose must be taken into account in the interpretation of any study where the response to a range of mitogen doses is studied.

Adult↗
PubMed1978

In vitro mitogen stimulation of synovial fluid lymphocytes from rheumatoid arthritis and juvenile rheumatoid arthritis patients: dissociation between the response to antigens and polyclonal mitogens.

The in vitro responses to mitogens of synovial fluid lymphocytes obtained from eight patients with rheumatoid arthritis (RA) and eight patients with juvenile rheumatoid arthritis (JRA) were studied. The results were compared to the transformation of the patient's peripheral blood lymphocytes stimulated with the same mitogens. Both RA and JRA synovial fluid lymphocytes showed a low transformation to the polyclonal mitogens PHA and PWM with a low ratio PHA-response/PWM-response. The stimulatory effect of purified protein derivative of tuberculin (PPD) was high, whereas a Candida albicans antigen preparation gave a more variable stimulation of the synovial fluid lymphocytes. In some patients the complete mitogen transformation profile of lymphocytes obtained from synovial fluid, synovial tissue and peripheral blood was studied. The results of the synovial fluid and tissue lymphocytes were similar.

Antigens↗
PubMed1976

Extent of mitogen receptor occupancy and modulation of mitogen receptor exposure: possible mechanisms for the regulation of cell growth.

125I-Insulin was used as a model mitogen to examine the relationships of mitogen receptor occupancy and exposure in controlling cell replication. Labeled hormone was bound to substratum-attached, confluent fibroblasts with two affinities, K1 approximately equal to 2 X 108 M-1 and K2 approximately equal to 0.8 X 107 M-1. Approximately 9,000 receptors per cell were calculated from a scatchboard plot analysis with 80% of them of the affinity type. Treatment of confluent fibroblasts with 1.0 to 10 microng/ml of trypsin for 10 min increasd the number of exposed K2 sites by a factor of 2 to 3. Culturing the fibroblasts in the absence of serum for 12 to 24 hr also increased the quantity of exposed K2 sites to 60,000 per cell. The addition of unlabeled insulin to untreated, trypsin-treated, or serum-starved fibroblasts resulted in a stimulation of 2-deoxyglucose transport and thymidine incorporation activity that was proportional to the observed level of 125I-insulin binding. The quantity of exposed insulin receptors on uninfected fibroblasts decreases as the cell culture density increases. Hormone binding to B77 virus-transformed fibroblasts also decreases with culture density but plateaus at a density of 6 X 105 cells/plate. This resulted in a 2- to 3-fold difference in the level of exposed receptors between the uninfected and virus-transformed cells in confluent cultures, and proportionally higher rates of sugar transport and thymidine incorporation activity. Trypsin treatment and 12 hr of growth in the absence of serum did not result in an increase in the level of recepto exposure in the virus-transformed cells. The results of this study suggest that the pleotypic events associated with the stimulation of cell replication as represented by sugar transport and DNA synthesis are dependent upon and proportional to mitogen receptor occupancy. The control of cell replication, however, appears to be linked by a presently unknown mechanism with the degree of exposure of mitogen recipotrs. Receptor concentration is high and is similar in rapidly growing uninfected and virus-transformed cells, but the subsequent decrease observed with an increase in culture density reaches an early plateau for the transformed cells. This difference in exposed receptors could provide the growth advantage that is the hallmark of transformed cells.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1978

[Action of various mitogens (phytohemagglutinin, cocanavalin A, pokeweed mitogen) on a purified human B- and T-lymphocyte population mediating spontaneous rosette formation].

The activity of various most widely used "polyclonal" mitogens, such as PHA, Con A and PWM on human peripheral blood lymphocyte subpopulations, after separation into the two main functional classes (B and T), was investigated. For separating the lymphocyte subclasses, the E-rosette formation technique has been followed, using the gradient centrifuged pellet and supernatant respectively. For the mitogens' activity evaluation, micro-culture system has been performed and 3H thymidine uptake has been assessed. The PHA has been shown to be much more active on the T lymphocyte subclass, though the mitogen cannot be kept very selective. Very much higher activity on the T subclass shows the Con A, which could be considered selective, if we hypothesize an at least partial receptor competition at lymphocyte membrane level between the mitogen and sheep erythrocytes. The PWM has been found very little active and not specific for either lymphocyte subclass.

Adult↗
PubMed1977

The necessity for T cell help for human tonsil B cell responses to pokeweed mitogens: induction of DNA synthesis, immunoglobulin, and specific antibody production with a T cell helper factor produced with pokeweed mitogen.

Human B lymphocytes obtained from tonsils do not proliferate when stimulated with pokeweed mitogen. A soluble factor produced from T cells cultured with pokeweed mitogen stimulates B cells to synthesize DNA and differentiate into immunoglobulin producing cells. This PWM produced supernatant induced a PFC response to SRBC. The T cell supernatant activity is produced within 12 hr of stimulation in the presence of serum and without a requirement for T cell division. Optimal stimulation of B cells occurred at 7 to 9 days of culture. This helper factor activity eluted postalbumin from a column of Sephadex G-200. Insolubilized pokeweed mitogen was not mitogenic for B cells. The continuous presence of the lectin in culture was not required for B cell proliferation or for immunoglobulin synthesis.

Antibody Specificity↗
PubMed1979

Adherent cells as targets in mitogenic T-lymphocyte stimulation: replacement of lymphocyte-bound mitogens by nonmitogenic substances.

The sequence of events in mitogenic T-lymphocyte activation was investigated by employing purified mouse peritoneal adherent cells and T-lymphocyte populations. After treatment of adherent cells with the oxidizing agents sodium periodate or neuroaminidase plus galactose oxidase and removal of the mitogens, the cells acquired the ability to stimulate purified T-lymphocytes added subsequently. For this process of T-lymphocyte activation, the additional presence of the membrane interacting substances polyethylene glycol, dextran, nonmitogenic Helix pomatia agglutinin, or inactivated sendai virus was required. Lysates of mitogen-treated peritoneal adherent cells were able to replace the adherent cells in the cultures.

Animals↗
PubMed1976

Effect of lectins on the levels of cAMP and cGMP in guinea pig lymphocytes: early responses of lymph node cells to mitogenic and non-mitogenic lectins.

Guinea pig lymph node lymphocytes were reacted with two mitogenic lectins (LcL-A or PHA) and two nonmitogenic lectins (AbL or WGA)m and the levels of cAMP and cGMP were determined during 30 min of culture. Various concentrations of LcL-A and PHA caused modest (1.5 to 2-fold) rises in cAMP levels. However, the rise in cAMP did not correlate with the degree of mitogenicity. AbL caused a greater rise in cAMP than the mitogenic lectins whereas WGA had no effect on cAMP levels. None of the four lectins causes an appreciable (i.e., greater than 1.5-fold) change in cGMP levels. There does not seem to be any positive correlation between early changes of cAMP and/or cGMP and mitogenesis.

Animals↗
PubMed1979

Inactivation of the mitogenic property of pokeweed mitogen by erythrocytes.

In whole blood culture, pokeweed mitogen (PWM) is unable to stimulate human lymphocytes. This is because the mitogenic property of PWM is inactivated by erythrocytes, presumably due to absorption. The inactivation was observed with as few as 5 x 10(6)/ml of human erythrocytes. Therefore, when PWM is used to study the functions of human lymphocytes, especially of suppressor T lymphocytes, erythrocytes should be removed from lymphocyte preparations for accurate analysis.

Absorption↗
PubMed1977

Nocardia water-soluble mitogen and lipopolysaccharide. Comparative study of two adjuvants and B-cell mitogens in mice.

The activity of Nocardia water-soluble mitogen (NWSM) and LPS were compared in several experimental systems, since both compounds are B-cell mitogens and polyclonal activators in vitro. The results reported here demonstrated that NWSM like LPS also has a strong adjuvant activity in vivo if administered in saline with a strong antigen (heterologous red blood cells) or even with a weak immunogen such as theta alloantigen. However, in contrast to LPS, NWSM administered to mice failed to induce in vivo proliferation of lymphocytes, polyclonal activation and PFC against syngeneic bromelain-treated erythrocytes and thymocytes. It is possible therefore, that different mechanisms may be responsible for adjuvant activity of NWSM and LPS.

Adjuvants, Immunologic↗
PubMed1979

Mitogenic proteins of pokeweed. II. The differentiation of human peripheral blood B lymphocytes stimulated with purified pokeweed mitogens (Po-2 and Po-6) from pokeweed, Phytolacca octandra.

Purified pokeweed mitogens, Po-2 and Po-3, extracted from Phytolacca octandra, stimulated plasma cell formation in cultures of human peripheral blood lymphocytes. Plasma cell formation did not occur in cultures of purified B cells but was dependent on T-cell help. High T-cell numbers, however, suppressed plasma cell formation in mixed B- and T-cell cultures stimulated with Po-2. T-cell helper function was exerted across a major histocompatibility barrier and was not dependent on T-cell proliferation. Soluble helper factor(s) from activated T cells were not demonstrated. Po-3 was an effective B-cell stimulant only at concentrations between 0.1 and 1.0 micrograms/ml. In contrast, relatively high concentrations of Po-2 (50--100 micrograms/ml) were required to induce B-cell differentiation. More plasma cells were generated in Po-2-stimulated cultures than in Po-3-stimulated cultures and this was thought to reflect the more aggregated state of Po-2.

B-Lymphocytes↗