Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “PHA”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 235 records · Page 13Linked to original sources
PubMed1987

Characterization of PHA and anti-T3 induced transduction mechanisms in a human T-cell leukaemia line.

Stimulation of the T-cell line JURKAT with PHA or anti-T3 antibody leads to a rapid and sustained rise of cytosolic free Ca2+, as determined by quin2 fluorescence measurements. Pertussis toxin and N-ethylmaleimide, substances known to inactivate a regulatory N-protein, caused partial to complete inhibition of the cytosolic free Ca2+ response induced both by anti-T3 or PHA. The high cytosolic free Ca2+ level induced by anti-T3 or PHA declined more rapidly after addition of phorbol ester, phorbol myristate acetate (PMA). PMA did not affect cytosolic free Ca2+ changes induced by ionomycin indicating that the effect of PMA is due to a direct inhibitory effect on a transduction mechanism and not to activation of Ca2+ extrusion. Our data suggest that a regulatory N-protein is involved in the transduction of the PHA and anti-T3 response into a rapid and sustained elevation of cytosolic free Ca2+. Activation of protein kinase C by PMA modulates the calcium response in JURKAT cells, suggesting that protein kinase C may be involved in feedback regulation of the transduction mechanism.

Calcium↗
PubMed1996

Phytohemagglutinin-L (PHA-L) lectin surface binding of N-linked beta 1-6 carbohydrate and its relationship to activated mutant ras in human pancreatic cancer cell lines.

Alterations of the N-linked carbohydrate core structure of cell surface glycoproteins (beta 1-6 branching) can be detected by phytohemagglutinin (PHA-L) lectin binding and has been linked to tumor progression and K-ras activation in colon cancer. The purpose of this study was to determine the prevalence of this carbohydrate alteration and its relationship to K-ras activation in pancreatic cancer. Nine human pancreatic cancer cell lines and 4 colon lines as controls were grown under standard tissue culture conditions. K-ras genome analysis was performed by polymerase chain reaction amplification and sequencing. The proportion of cellular p21-ras bound to GTP (ras-GTP level) was determined using immunoprecipitation of 32P-labeled cell lysates followed by thin layer chromatography and phosphoimaging analysis. Lectin blot analysis was performed on crude membrane preparations. Sensitivity to lectins was assessed with cell culture thymidine incorporation. Of 9 pancreatic cancer lines tested, 3 had wild type K-ras, 2 had heterozygous and 4 had homozygous mutations in codon 12 of K-ras. These genotypes correlated strongly with the level of ras-GTP measured. K-ras mutants had increased levels of ras-GTP compared to wild-type cell lines. PHA-L binding to cell membranes correlated positively with ras-GTP levels in 7 out of 9 cell lines. PHA-L toxicity was greatest in cells with positive PHA-L reactivity on Western blotting. A positive correlation between the presence of K-ras mutation, increased ras-GTP level, and increased cell surface beta 1-6 N-linked carbohydrate exists in pancreatic cancer cell lines.

Concanavalin A↗
PubMed2006

Soluble factors from LPS- and PHA-activated PBMC induce MAPK, Stat1 and Stat3 phosphorylation in primary cultures of human term placental trophoblasts: implications for infection and prematurity.

Infection of the maternal vaginal tract is one of the single most important antecedents of premature labor. We have hypothesized that the abundant local synthesis of pro-inflammatory cytokines that occurs during infection may disrupt the delicate "immunological cross-talk" that must occur between maternal and fetal tissues in order to carry pregnancy to term. These experiments were undertaken as part of a larger study directed at testing that hypothesis. We prepared primary cultures of human trophoblasts from term placentas. Cell cultures were stimulated with conditioned medium from resting, PHA or LPS-activated peripheral blood mononuclear cells (PBMC). Medium with LPS or PHA at the same concentration as that used to stimulate the PBMC was used as an additional control. Lysates were subjected to western blotting for activated forms of the mitogen-activated protein kinases (MAPK), Stat1, and Stat3. Western blotting showed phosphorylation of the Jun kinase (JNK), p38, and Erk1/Erk2 MAPK in trophoblasts incubated with conditioned medium from LPS or PHA-activated PBMC but not from medium from resting PBMC, or with PHA or LPS alone. Phosphorylation could be detected as early as 5 min and was still observable by 10 min, the latest time point tested. Similarly, Stat1 and Stat3 phosphorylation was observed within 10 min of exposure to conditioned medium and was still observable 10 min after exposure. Immunohistochemistry also demonstrated nuclear translocation of both Stat1 and Stat3 after stimulation of trophoblasts with medium from activated PBMC. These findings are compatible with the hypothesis that immunologic balance at the maternal-fetal interface is maintained by ongoing "cross-talk" between the fetus (and fetally-derived tissues) and the maternal immune system. Infection of the maternal vaginal tract may disrupt this delicate immunologic balance, initiating inflammatory events that ultimately result in preterm labor.

Enzyme Activation↗
PubMed2004

An early pharyngeal muscle enhancer from the Caenorhabditis elegans ceh-22 gene is targeted by the Forkhead factor PHA-4.

Caenorhabditis elegans pharyngeal muscle development involves ceh-22, an NK-2 family homeobox gene related to genes controlling heart development in other species. ceh-22 is the earliest known gene expressed in the pharyngeal muscles and is likely regulated directly by factors specifying pharyngeal muscle fate. We have previously implicated the ceh-22 distal enhancer in initiating ceh-22 expression. Here we analyze the distal enhancer using functional and comparative assays. The distal enhancer contains three subelements contributing additively to its activity, and functionally important regulatory sequences are highly conserved in Caenorhabditis briggsae. One subelement, termed DE3, is strongly active in the pharyngeal muscles, and we identified two short oligonucleotides (de199 and de209) contributing to DE3 activity. Multimerized de209 enhances transcription similarly to DE3 specifically in the pharyngeal muscles, suggesting it may be an essential site regulating ceh-22. de209 binds the pan-pharyngeal Forkhead factor PHA-4 in vitro and responds to ectopic pha-4 expression in vivo, suggesting that PHA-4 directly initiates ceh-22 expression through de209. Because de209 enhancer activity is primarily limited to the pharyngeal muscles, we hypothesize that de209 also binds factors functioning with PHA-4 to specifically activate ceh-22 expression in pharyngeal muscle.

Animals↗
PubMed1975

Cellular repopulation and recovery of the phytogemagglutinine (PHA) responding cell pool in the thymus of sublethally irradiated mice.

Cellular repopulation and recovery of PHA reactivity was investigated in the thymus of mice exposed to 400 R either on the whole body or with one leg protected. In the whole body irradiated cases both the cellular repopulation and the restoration of PHA reactivity in the thymus showed a cyclic pattern: an initial depression and a subsequent first recovery being followed by a secondary cellular depletion and decrease of reactivity before another recovery phase started. The phase of the secondary decrease lasted fo a similar period for both the cell number and reactivity, but was shifted in time and the reduction in reactivity began some 12 days later than that in the cell number. In the leg-shielded animals, the cellular repopulation progressed without cyclic changes, but the recovery of PHA reactivity maintained a cyclic pattern. However, due to a smaller secondary decrease, it was less pronounced than in the whole body irradiated cases. During the aging of mice from 50 to 90 day old, the cell number in the involuting thymus decreased to half of the original. The decrease in the cell population was associated with an about four-fold increase of PHA reactivity. The results were discussed in regard to the origin of the immunoreactive thymic cells. Arguments were presented in favour of the hypothesis that both the reactive and nonreactive cells originate from precursors in common, but require different lengths of time for maturation.

Aging↗
PubMed2000

Effects of phytohemagglutinin (PHA) on the structure of midgut epithelial cells and localization of its binding sites in western tarnished plant bug, Lygus hesperus Knight.

Two histological techniques, bright-field microscopy and immunofluoresecent staining were used to elucidate the lethal effect, target tissues and binding sites of phytohemagglutinin (PHA), a lectin from Phaseolus vulgaris L., on the western tarnished plant bug. Bright-field microscopy showed that the nuclei of the foregut epithelial cells were slightly disrupted and elongated but the lumen of the gut was open. The midgut epithelial cells also showed severe disruption. However, the cells of the first and the third ventriculus were much more sensitive to PHA than those in the second ventriculus. The epithelial cells in these two regions were severely disrupted and swollen toward the lumen, resulting in complete closure of the gut. Most of the cells in these regions contained two nuclei. Also, interestingly, the epithelial cells of the hindgut were drastically disrupted leading to complete closure of the lumen. Immunofluoresecent images from the midgut showed that strong binding occurred on brush-border microvilli of the epithelial cells only within the first and third ventriculi, and some signals within their cytoplasm. Thus, immunofluoresecent studies showed that PHA binds preferentially to the midgut region which demonstrates the most severe effects, and that these cells may endocytose the bound PHA.

Journal Article↗
PubMed1999

A combination of dietary protein depletion and PHA-induced gut growth reduce the mass of a murine non-Hodgkin lymphoma.

The results presented in this study show that a switch from a non-protein diet (NPD) to one of a normal protein content (LA) on the day of subcutaneous injection of non-Hodgkin lymphoma tumour cells greatly favoured the development and growth of the tumour. Interestingly, however, inclusion of the plant lectin phytohaemagglutinin (PHA) in the LA diet appeared to compete with the effect of switch to the protein-rich diet, resulting in decreased tumour size and an increased incidence of necrosis. PHA was shown to induce hyperplasia of the gut even in the presence of the growing tumour. This observation together with the fact that gut hyperplasia also occurred in animals which were fed NPD supplemented with PHA, indicated the strength of PHA as a growth signal. It would seem likely that this 'normal' growth is able to compete with the tumour for important growth factors and nutrients, including polyamines, effectively starving the tumour for these molecules and resulting in its decreased rate of proliferation.

Animals↗
PubMed1979

Response of T lymphocytes to phytohaemagglutinin (PHA) and to cancer-tissue-associated antigens, measured by the intracellular fluorescence polarization technique (SCM test).

Human peripheral-blood mononuclear cells, separated by Isopaque-Ficoll flotation and E-rosette formation, were tested by the fluorescein fluorescence polarization method of Cercek & Cercek (the SCM test). The response to stimulation with PHA or cancer tissue leads to a decreased polarization value TP). The responding cells were present in the T-cell fraction (E-rosette-forming cells), which contained less than 10% macrophages and less than 1% cells with surface-bound Ig. Control experiments with the non-T-cell fraction gave different response patterns. The response of T cells from apparently healthy donors and patients with and without cancer were compared. All of the group of 16 healthy persons had a polarization value (P) which decreased (mean +/- s.e. = 23% +/- 2) after PHA stimulation, compared with no or little decrease after stimulation with cancer tissue, giving cancer indices (P cancer/PPHA) of 1.15--1.56. In 13 patients with carcinoma of the colon, stimulation with PHA produced little decrease of polarization, while stimulation with colonic cancer tissue decreased the polarization in all cases (mean +/- s.e. = 25% +/- 2). The corresponding cancer indices were 0.61--0.86. Seven of 10 colonic-cancer patients tested against ovarian cancer tissue did not respond, whilst 3 patients in this group responded and had a cancer index less than 1.0. Three patients with non-malignant diseases had response patterns similar to those of healthy persons, except for the lack of PHA response in the patient with ulcerative colitis. This method seems to open up new possibilities for evaluation of cancer patients, although further studies including many more patients are needed before any conclusion can be drawn as to the validity of the test.

Adenocarcinoma↗
PubMed2002

Prolactin induces enhanced interferon gamma release in peripheral whole blood after stimulation with either PHA or LPS.

A number of recent studies have demonstrated the importance of prolactin as a key mediator in immune-neuroendocrine communication. Using a whole blood assay and various concentrations of prolactin, we stimulated cell cultures with either the plant lectin PHA or the endotoxin LPS, a widespread agent in common infectious diseases. Studying 15 healthy blood donors we found that human recombinant prolactin, at concentrations from 5 ng/ml to 100 ng/ml, significantly amplified IFN-gamma yields after stimulation with either PHA or LPS. PHA-stimulated cultures revealed a significant dose-dependent enhancement of IFN-gamma release. Our results indicate that prolactin can upregulate IFN-gamma secretion from immune cells in whole blood cell cultures in response to both PHA or LPS. Since IFN-gamma is suspected to play a key role in the cytokine cascade, amplifying the toxic effect of other pro-inflammatory cytokines and ultimately leading to augmented inflammatory tissue damage, our findings point to a modulatory role of prolactin in infection. Special interest should therefore be directed towards any naturally occurring hyperprolactinemia, caused for instance by stress, a number of drugs, and some chronic diseases.

Blood Cells↗
PubMed1988

The effect of low-dose irradiation on unstimulated and PHA-stimulated human lymphocyte subsets.

A culture system was used to evaluate the radiosensitivity of CD4+ and CD8+ T cells, Leu 19+ cells, and B cells obtained from normal adult males. Unstimulated CD8+ lymphocytes (D0 = 55 cGy) were twice as radiosensitive as CD4+ cells (D0 = 115 cGy). B cells had an intermediate radiosensitivity (D0 = 100 cGy). Leu 19+ cells were much more radioresistant and expressed a D0 of 550 cGy. When lymphoid cells were irradiated 1 or 4 days before phytohemagglutinin (PHA) stimulation, they were more radiosensitive than if they were first stimulated with PHA and then irradiated. When lymphoid cells were irradiated 1 h after PHA stimulation each lymphocyte subset was characterized by an increase in the D0 to 150 cGy for B cells to 290 cGy for CD4+ cells, and to 240 cGy for CD8+ cells. In contrast, Leu 19+ cells exhibited a decrease in their D0 to 290 cGy after they were stimulated by PHA.

Adult↗
PubMed1997

Therapeutic immunostimulating effects of plant mitogens exemplified by the L4 isolectin of PHA.

A sizable body of evidence has accumulated showing that the characteristics of certain plant mitogens should endow them with valuable immunomodulating effects. Immune stimulation would be the fundamental function operating through the broad consequences of nonspecific T cell activation following binding with their CD3 or CD2 molecules. Based on in vitro evidences that PHA, operating through the LDCC pathway, might kill any tumor target if it remains present in adequate concentration, the administration of mitogens for cancer therapy would be rational, and the same mechanism should also justify these agents for treatment of certain infections. Being nonerythroagglutinating, although leukoagglutinating in higher concentrations, PHA-L4 serves as a suitable model for immunostimulating activities of the mitogens that can be applied directly or as in vitro activators of adoptive leukocytes. The PHA skin test can be utilized to gauge the serum levels of inhibitory glycoproteins that become elevated in a number of the disorders treatable by the mitogen, thus facilitating necessary dosage modifications. While PHA is the only mitogenic lectin that has been tested clinically, Con A and PWM are the two most widely studied among the alternatives, with others also available and many undoubtedly awaiting discovery. The development of practical methods for producing industrial quantities of nonagglutinating mitogens in pure form should be the goal, and accomplishing the latter might also answer certain hypersensitivity concerns.

Adjuvants, Immunologic↗
PubMed1998

Immunosuppressive applications of PHA and other plant mitogens.

Phytohemagglutinin was prominent in the evaluation of the immunosuppressive effects of mitogenic lectins that started in 1965 and continued for two decades. Basic studies elucidated the inhibitory actions of PHA on humoral and cellular immune responses in mice, rats, and guinea pigs. Some suppressive effects of this and other mitogens including lentil lectin and Con A were demonstrated on renal, skin, pancreas, and heart allograft rejections in mice, rats, and dogs. In addition to their inherent suppressive activities, these substances have been shown to potently augment the suppression generated by conventional agents. More relevant to tolerance-inducing modulations, the Rigas group showed that in vitro incubation of the parental spleen cells with PHA in the F1 hybrid model before giving them to the F1 mouse virtually abolished the GvH responses. Their explanation was that the donor cells were rendered unresponsive by their reversion to an immature state in which they lost the essential surface receptors. Similar spleen cell suppression was generated by systemic administration of PHA to the parental donor prior to their administration. A method is proposed here for establishing tolerance to either newly introduced or firmly established antigens applying the L4 isolectin of PHA to make non-reactive all T lymphocytes that remain functional in conjunction with full suppression by conventional agents. During the vulnerable period of drug-induced suppression, the host would be protected from infection and bleeding by full nonspecific proliferative activation of the lymphoid and myeloid systems. The establishment of allograft tolerance by preemptive inhibition of responses to newly introduced transplant antigens would be easier to achieve than the reversal of firmly established responses to antigens involved in GvH reactions and autoimmune diseases. The studies of von Boehmer and Kisielow in a transgenic mouse model confirmed that clonal deletion does occur in the thymus whereby corresponding specific thymocytes are destroyed when they encounter self-antigens. Their work suggested that tolerance to self-antigens might be established if immune responses against putative antigen peptides were blocked sufficiently that they would be released to reach the central or peripheral residence sites of their immunologically reactive clones for deletion to occur. This approach to suppressive therapy would be useful for managing the problems of allograft rejection, GvH reactions, and autoimmune disorders even if they fell short of generating complete tolerance. Suppressive treatment with mitogens would also be indicated for the immune-related group of aplastic anemias, but a discussion of these disorders will be deferred to a separate article because of certain aberrations they present.

Animals↗
PubMed1995

The effect of PHA stimulation on lymphocyte sub-populations in whole-blood cultures.

Although lymphocytes in phytohaemagglutinin (PHA)-stimulated whole blood cultures are routinely used to assess genotoxin-induced chromosome damage, very little information is available on the effect of PHA on the various cell populations present, and there appear to be no data for the protocols used in routine genotoxicity assays. In this study, we used flow cytometric analysis to examine the size/complexity of the white blood cell (WBC) population and the expression of key antigenic markers by the lymphocytes over a 96-h period following PHA stimulation. The changes in the WBC population are complex, and would seem to represent different populations dying out, remaining static or starting to divide. The initial decrease seen in overall cell numbers probably reflects death of the neutrophil and monocyte populations. The subsequent increase in cell numbers appears to be due to division of the lymphocytes and, by 96 h post-stimulation, they comprise about half the total cell number and, as expected, > 90% are activated T-cells; it seems reasonable to assume that these represent the target cells in genotoxicity assays. Although we do not suggest that these findings should alter the routine conduct of clastogenicity assays using PHA-stimulated whole-blood cultures, they indicate that such tests are empirical and that closer investigation will only confirm their relatively imprecise nature.

Cell Division↗
PubMed1981

Sequence complexity and diversity of polyadenylated RNA molecules of human normal resting, PHA-stimulated and leukemic lymphocytes.

The abundance and complexity of total poly(A)+RNA of human normal unstimulated lymphocytes, PHA-stimulated and leukemic lymphocytes were examined using the cDNA-poly(A)+ RNA hybridization technique. It was found that in both PHA-stimulated and leukemic lymphocytes the complexity of total poly(A)+RNA is strongly reduced in respect to normal unstimulated lymphocytes. The differences is due to a small portion, by weight, of high complexity sequences, suggesting the involvement or nuclear, not necessarily transcriptional, events. Moreover the heterologous hybridizations show that: 1) in PHA-stimulated lymphocytes there is a set of highly abundant sequences which are represented in normal and leukemic lymphocytes at a very reduced rate; 2) the sequences abundant in normal unstimulated lymphocytes are less represented in leukemic lymphocytes; the converse also is true, but at a lower extent. On the basis of available data, it is suggested that the observed changes in the abundance pattern of PHA-stimulated lymphocytes may be related mainly to a difference in the half-life of the mRNAs, while those of leukemic lymphocytes require some transcriptional or post-transcriptional nuclear event.

Base Sequence↗
PubMed1985

The effect of indomethacin treatment on lymphocyte PHA reactivity in healthy controls and patients with lymphoma and sarcoidosis.

Lymphocytes from healthy volunteers who took indomethacin orally for 3 d showed an enhanced in vitro response to phytohaemagglutinin (PHA). When indomethacin was added in vitro, lymphocytes from healthy controls showed similar but more consistent increases of PHA responses than lymphocytes from patients with sarcoidosis or lymphoma. Moreover, the enhancing effect of indomethacin was by and large more pronounced in those patients who had relatively normal PHA lymphocyte responses in the absence of indomethacin, and the presence of indomethacin failed in most instances to increase subnormal responses to normal control levels. These findings are not consistent with the notion that increased prostaglandin synthesis is the principal cause of subnormal PHA reactivity of lymphocytes from patients with sarcoidosis or lymphoma.

Adolescent↗
PubMed1976

Genetic control of antibody responses to PHA in inbred rats.

Phytohemagglutinin (PHA-P; Difco) contains four immunogenic components. The antibody response in rats to two of these components is shown to be genetically determined: AS rats are high responders and BN rats are low responders to both antigens. Responsiveness to the two components segregates independently as autosomal, dominant traits in a manner that is compatible with a one-gene hypothesis for both responses. The antibody response to the mitogenic fraction of PHA segregates together with the in vitro mitogenic response to PHA and to other mitogens. These responses are not linked to the major histocompatibility complex (MHC) of the rat. The antibody response to a nonmitogenic fraction from PHA is, however, linked to the MHC.

Animals↗
PubMed1976

Migration inhibitory effect of cell-free supernatants from PHA-activated cultures of human mononuclear leukocytes.

A two-step test for the demonstration of phytohaemagglutinin (PHA)-induced production of migration inhibitory factor (MIF) was investigated. In the first step, human purified mononuclear leukocytes were activated by incubation with PHA for 1 h. Then the cells were washed thoroughly and cultured for 1 to 4 days in TC medium without PHA. In the second step, the MIF-activity of the cell-free culture supernatants was tested on non-separated human leukocytes. The migration inhibition reaction was demonstrated by the agarose migration technique. The supernatants might have been contaminated by PHA, but it was shown that such contamination would be unable to cause any appreciable migration inhibition of the indicator leukocytes.

Cell Migration Inhibition↗
PubMed1991

Innervation of Entorhinal Principal Cells by Neurons of the Nucleus Reuniens Thalami. Anterograde PHA-L Tracing Combined with Retrograde Fluorescent Tracing and Intracellular Injection with Lucifer Yellow in the Rat.

The innervation of dendrites of identified entorhinal principal cells by fibres originating in the nucleus reuniens thalami was studied in the rat. The lectin Phaseolus vulgaris-leucoagglutinin (PHA-L, anterograde tracer) was injected into the nucleus reuniens and the fluorescent dye Fast Blue (retrograde tracer) into the hippocampus. After survival, perfusion-fixation and the preparation of brain slices, entorhinal neurons retrogradely labelled with Fast Blue were intracellularly injected with the dye Lucifer yellow to introduce a specific marker into their dendrites. The transported PHA-L and the injected Lucifer yellow were visualized through dual peroxidase immunohistochemistry. Varicosities on PHA-L labelled reuniens fibres abut ascending and descending Lucifer yellow-filled secondary dendrites of multipolar and pyramidal principal entorhinal neurons that possess either spiny or sparsely spiny dendrites, but they do not appose the perikarya of these cells. In the electron microscope, PHA-L labelled boutons in the entorhinal cortex were observed forming asymmetrical synaptic contacts with dendritic spines (50%) or shafts (50%). The results indicate that direct thalamic input occurs on dendrites of neurons in the entorhinal cortex which project to the hippocampus.

Journal Article↗