Activation of T and B lymphocytes by insoluble phytomitogens

Immune response of heterologous versus homologous prime-boost regimens with adenoviral vectored and mRNA COVID-19 vaccines in immunocompromised patients

Due to rare but major adverse reactions to the AstraZeneca adenoviral ChAdOx1-S-nCoV-19 vaccine (ChAd), German health authorities recommended adults under 60 who received one dose of ChAd, to receive a second dose of the BioNTech mRNA BNT162b2 vaccine (BNT) as a booster. Studies in the general population suggest an enhanced efficacy of the heterologous (ChAd-BNT) compared to the homologous (BNT-BNT) vaccination regimen. However, an analysis of the efficacy in patient populations with a high risk of severe COVID-19 due to acquired immunodeficiency is still missing. We therefore compared both vaccination regimens in healthy controls, patients with gynecological tumors after chemotherapy, patients on dialysis and patients with rheumatic diseases concerning the humoral and cellular immune response. The humoral and cellular immune response differed substantially in healthy controls compared to patients with acquired immunodeficiency. Overall, the most significant differences between the two immunization regimens were found in neutralizing antibodies. These were always higher after a heterologous immunization. Healthy controls responded well to both vaccination regimens. However, the formation of neutralizing antibodies was more pronounced after a heterologous immunization. Dialysis patients, on the other hand, only developed an adequate humoral and particularly cellular immune response after a heterologous immunization. Tumor and rheumatic patients also - to a weaker extent compared to dialysis patients - benefited from a heterologous immunization. In conclusion, the heterologous COVID-19 vaccination regimens (ChAd-BNT) seem to have an advantage over the homologous vaccination regimens, especially in immunocompromised patients such as patients with end-stage kidney disease treated with hemodialysis.

Structure-function and application of plant lectins in disease biology and immunity

Lectins are proteins with a high degree of stereospecificity to recognize various sugar structures and form reversible linkages upon interaction with glyco-conjugate complexes. These are abundantly found in plants, animals and many other species and are known to agglutinate various blood groups of erythrocytes. Further, due to the unique carbohydrate recognition property, lectins have been extensively used in many biological functions that make use of protein-carbohydrate recognition like detection, isolation and characterization of glycoconjugates, histochemistry of cells and tissues, tumor cell recognition and many more. In this review, we have summarized the immunomodulatory effects of plant lectins and their effects against diseases, including antimicrobial action. We found that many plant lectins mediate its microbicidal activity by triggering host immune responses that result in the release of several cytokines followed by activation of effector mechanism. Moreover, certain lectins also enhance the phagocytic activity of macrophages during microbial infections. Lectins along with heat killed microbes can act as vaccine to provide long term protection from deadly microbes. Hence, lectin based therapy can be used as a better substitute to fight microbial diseases efficiently in future.

Inhibition of human T-cell proliferation by mammalian target of rapamycin (mTOR) antagonists requires noncoding RNA growth-arrest-specific transcript 5 (GAS5)

The central importance of the serine/threonine protein kinase mTOR (mammalian Target of Rapamycin) in the control of cell growth and proliferation is well established. However, our knowledge both of the upstream pathways controlling mTOR activity and of the downstream events mediating these effects is still seriously incomplete. We report a previously unsuspected role for the nonprotein-coding RNA GAS5 in the inhibition of T-cell proliferation produced by mTOR antagonists such as rapamycin. GAS5 transcripts are up-regulated during growth arrest and after rapamycin treatment, and GAS5 has recently been shown to be necessary and sufficient for normal T-cell growth arrest. Down-regulation of GAS5 using RNA interference protects both leukemic and primary human T cells from the inhibition of proliferation produced by mTOR antagonists. The GAS5 transcript is a member of the 5' terminal oligopyrimidine class of RNAs, which is specifically controlled at the level of translation by the mTOR pathway, and the effects of GAS5 on the cell cycle provide a novel and important link to the control of proliferation. These observations point to a significant advance in our understanding of the mechanism of action of mTOR inhibitors, which is likely to lead to improvements in immunosuppressive and cancer therapy.

Protein phosphatase 4 regulates apoptosis in leukemic and primary human T-cells

The control of T-cell survival is of overwhelming importance for preventing leukemia and lymphoma. The present report demonstrates that the serine/threonine protein phosphatase PP4 regulates the survival of both leukemic T-cells and untransformed human peripheral blood T-cells, particularly after treatment with anti-leukemic drugs and other cytotoxic stimuli. PP4-induced apoptosis is mediated, at least in part, through de-phosphorylation of apoptosis regulator PEA-15, previously implicated in the control of leukemic cell survival. PP4 activity significantly affects the mutation rate in leukemic T-cells, indicating that PP4 dysfunction may be important in the development and progression of leukemia.

Growth arrest in human T-cells is controlled by the non-coding RNA growth-arrest-specific transcript 5 (GAS5)

The control of growth of lymphocyte populations is crucial to the physiological regulation of the immune system, and to the prevention of both leukaemic and autoimmune disease. This control is mediated through modulation of the cell cycle and regulation of cell death. During log-phase growth the rate of proliferation is high and there is a low rate of cell death. As the population density increases, the cell cycle is extended and apoptosis becomes more frequent as the population enters growth arrest. Here, we show that growth-arrest-specific transcript 5 (GAS5) plays an essential role in normal growth arrest in both T-cell lines and non-transformed lymphocytes. Overexpression of GAS5 causes both an increase in apoptosis and a reduction in the rate of progression through the cell-cycle. Consistent with this, downregulation of endogenous GAS5 inhibits apoptosis and maintains a more rapid cell cycle, indicating that GAS5 expression is both necessary and sufficient for normal growth arrest in T-cell lines as well as human peripheral blood T-cells. Control of apoptosis and the cell cycle by GAS5 has significant consequences for disease pathogenesis, because independent studies have already identified GAS5 as an important candidate gene in the development of autoimmune disease.

The C-terminal tetrapeptide of beta-endorphin (MPF) enhances lymphocyte proliferative responses

Human MPF (Lys-Lys-Gly-Glu) stimulates the proliferative response of human lymphocytes to the T-cell mitogen concanavalin A by 121-751% in the concentration range 10(-11)-10(-4) M; the peak effect is at 10(-8) M, lower or higher concentrations eliciting reduced responses, i.e. the dose-response curve is bell-shaped. Species specificity is high. Human MPF similarly stimulates rat lymphocytes, but the peak effect is seen at a 100-fold higher dose (10(-6) M). Rat MPF (Lys-Lys-Gly-Gln) has a peak effect at 10(-6) M with human lymphocytes, but the peak effect with rat lymphocytes is at a 1000-fold lower dose (10(-9) M). Truncated forms of the MPFs (Gly-Glu, Gly-Gln, Gly, Glu, Gln) and opioid peptides (beta-endorphin, [Leu] and [Met]enkephalin) show insignificant or only weak stimulatory or inhibitory effects. These results suggest that MPF acts via specific non-opioid receptors located on lymphocytes and that endogenously released MPF may have an important role in the functioning of the immune system.

Scatchard analysis of fluorescent concanavalin A binding to lymphocytes

Standard Scatchard analysis of ligand binding to cell receptors requires the use of isotopes and is imprecise at low ligand concentrations. To evaluate the feasibility of Scatchard analysis via fluorescence flow cytometry, the binding of fluorescein isothiocyanate-derivatized concanavalin A (FITC-ConA) to murine lymphocytes at 4 degrees C was compared to 125I-ConA binding. A FACS IV flow cytometer (Becton-Dickinson, Mountain View, CA) was used for analysis of cells after fluorescent ligand binding. A simple spectrophotometric technique was used to calibrate the relation between cytometer-determined fluorescence and ligand binding per cell. As FITC-ConA binding showed a quasi-Gaussian distribution, the mean number of molecules bound per cell was easily calculated. Scatchard analysis of FITC-ConA binding yielded results (1.9 x 10(6) receptors/cell, K = 3.6 x 10(-15)) similar to those obtained with 125I-ConA (1.4 x 10(6) receptors/cell, K = 5.2 x 10(-15)). Cytometric Scatchard plots showed less scatter and seemed more precise, suggesting superiority to radioactive ligand measurements, particularly at low ligand concentrations.

Variations in the relative amounts of biotin-containing enzymes present in both tumorigenic and non-tumorigenic hybrid cells and other cell lines

The observation that radioactively labelled streptavidin binds to several biotin-containing enzymes in mammalian cells has led to the finding that there is considerable variation in the proportion of these enzymes present (namely beta-methyl crotonyl CoA; propionyl CoA; pyruvate and acetyl CoA, carboxylases). This is particularly striking when certain tumorigenic and non-tumorigenic hybrid cells are compared. It is found that there is a consistently higher proportion of pyruvate carboxylase in the tumorigenic hybrid cells. However, not all tumorigenic cell lines show this same characteristic and reasons for this are discussed. It is also shown that whilst the proportions of the four enzymes are apparently constant for a given cell type, there is a substantial degree of clonal variation and this is particularly so in tumorigenic cells in vitro. However, the more tumorigenic cells in a given population do show a higher proportion of pyruvate carboxylase. Also a range of cells derived from lymphoid tissue has been compared with normal human lymphocytes and considerable differences are again observed. The significance of these findings is considered in relation to other phenotypic properties of hybrid cells.

Induction of antitumor activities in spleen cells from mice and rats activated with lipopolysaccharide immobilized on beads

Lipopolysaccharides (LPS) were coupled to polystyrene beads in order to apply the LPS without toxicity. The antitumor activity of the LPS-immobilizing beads was studied in experiments in vitro and in vivo. In vitro studies showed that spleen cells from C3H/HeN mice stimulated by beads immobilizing LPS from Escherichia coli produced cytolytic activity as strong as that of lymphokine-activated killer (LAK) cells. Spleen cells from Sprague-Dawley rats stimulated by beads immobilizing LPS from Salmonella minnesota produced cytolytic activity stronger than that of LAK cells. However, spleen cells stimulated by beads immobilizing each component of the LPS separately could not induce cytolysis. Contact stimulation, even for a brief period, sufficed for cytolytic activity, and was enhanced by culture for 48-72 h. Through in vivo studies, the suppression of tumor growth and a prolongation of the survival time were observed in tumor-bearing mice injected with spleen cells activated by beads immobilizing LPS from E. coli, and in mice injected with LAK cells. The effect of the activated spleen cells was stronger than that of the LAK cells. In rats bearing metastatic tumors, spleen cells activated by beads immobilizing LPS from S. minnesota suppressed lung metastases more strongly than did LAK cells. These findings indicate that LPS immobilized by beads induced killer cells more strongly than interleukin-2. Ex vivo immunomodulation with LPS-immobilizing beads can be applied usefully as an anticancer treatment.

A comparison of the effects of various stimulatory agents on t-PA secretion by normal and malignant cell lines

Succinyl con A and acetyl con A both stimulated epithelial cells to produce similar yields of tissue plasminogen activator (t-PA) to those previously obtained with native con A. However, unlike con A, the derivatized lectins did not adversely affect cell morphology and viability, and cells treated with succinyl con A could secrete t-PA for a prolonged period. Con A and the two derivatives produced similar morphological effects in Bowes melanoma cells, but t-PA production was not increased. Elevated cyclic nucleotide concentrations did not affect t-PA production from epithelial cells, but calcium ionophore treatment generated t-PA yields similar to those obtained with lectins. Azacytidine, which enhanced t-PA production from epithelial cells, did not increase yields from Bowes melanoma cells, and also sodium butyrate, reported to increase t-PA yields from human endothelial cells, had no effect on either cell line.

Pitfalls in measuring fluorescence polarization in mitogen-stimulated T-lymphocytes

Fluorescence polarization measurements with the probe 1,6-diphenyl-1,3,5-hexatriene (DPH) were performed to detect changes in the fluidity of plasma membranes from T-lymphocytes stimulated with mitogens. When the cells were incubated with succinyl-concanavalin A an increase in fluorescence polarization was observed. This, however, could be shown to be due to the interaction of the mitogen with the label DPH and did not reflect changes in the plasma membrane. In purified plasma membranes a decrease rather than an increase of fluorescence polarization was observed.

Development of optimal conditions for lymphokine production by chicken lymphocytes

Chicken thymus, spleen, and bursa lymphocytes were isolated by different methods and incubated under differing conditions in order to obtain and characterize avian lymphokines. The biological activity of lymphokine-containing cell culture supernatants was measured by their antiviral activity (interferon(IFN)-units) and by their capacity to induce cytostatic effects in bone-marrow-derived macrophages (50% cytostasis-inducing dose, CID). Lymphokine production by thymus lymphocytes required concanavalin A (ConA)-stimulation, while spleen cells, when cultured at high density, released CID and IFN activities into the culture medium even without mitogen-stimulation. By way of comparison, the highest lymphokine content was found in the supernatant of lymphocyte cultures, which were incubated for 72 hours at 41 degrees C after stimulation with an optimal ConA dose. For stimulation of thymus lymphocytes 30 micrograms ConA/ml were found to be optimal, independent of serum content and cell density in the cultures. In contrast, the optimal ConA dose for spleen lymphocytes not only depended on the serum content but also on the cell density in the cultures and varied within a range of 2.5 micrograms and 45 micrograms ConA/ml.

Wheat germ agglutinin inhibits nerve fiber growth and concanavalin A stimulates nerve fiber initiation in cultures of dorsal root ganglia neurons

Treatment of dorsal root ganglion (DRG) neurons with the lectin wheat germ agglutinin (WGA; 25 micrograms/ml), which binds to N-acetylglucosamine containing glycoconjugates, inhibits nerve fiber growth in culture. DRG neurons treated with WGA have significantly reduced total output in nerve fiber length per neuron as well as reductions in the average length of the individual nerve fibers extended. The inhibition of nerve fiber growth by WGA is concentration-dependent, specific, reversible and not mimicked by treatment with several metabolic poisons. In contrast, treatment with the lectin concanavalin A (25 micrograms/ml), which binds to mannose-containing glycoconjugates, increases the number of nerve fibers produced per neuron. These results suggest that lectins which bind to distinct carbohydrate moieties can differentially regulate nerve fiber growth.

Correlation of interferon gamma inducing ability to sugar binding specificities of various lectins

Various lectins were examined to determine possible induction of gamma interferon (IFN-gamma) in human leukocytes. Among the seven positive lectins (Concanavalin A, pea lectin, lentil lectin, rice bran agglutinin, pokeweed mitogen, wheat germ agglutinin, phytohemagglutinin-P), six except rice bran agglutinin belonged to those which recognize carbohydrate chains connected to polypeptide through a glycosylamine linkage between N-acetylglucosamine (GlcNAc) and asparagine residues. The specificity of carbohydrate chain recognition of rice bran agglutinin, residual one positive lectin, has not been reported. Induction of IFN-gamma by wheat germ agglutinin, one of the positive lectins, was inhibited by the addition of GlcNAc during the induction, but not by the addition of glucose, galactose, alpha-methylmannose, N-acetylgalactosamine, N-acetylmannosamine, and lactose.

In vivo stimulation of nerve cells by phytohemagglutinin. II. Alterations in the rate of total and mRNA synthesis in the brain cortex of old rats

Bacto-phytohemagglutinin-P (PHA-P) was administered in form of a single intralumbar injection of 2 mg/100 g body weight dose to 24- to 28-mth-old female CGY rats. The accuracy of the injection technique was checked by adding 2% lidocaine to the injection mixture, which resulted in a transient and symmetric paralysis of the posterior limbs when reaching the cerebrospinal fluid. The total RNA content of the liver and brain cortex were measured, and phenolic extraction of RNA was performed the brain cortex. Poly(A) +RNA (mRNA) was separated from the total RNA of the brain cortex by oligo(dT)-cellulose chromatography. Pulse labeling with tritiated uridine was performed 45 min before killing the animals and the incorporation of the radiolabel was measured in the respective RNA classes and corrected for the nucleotide pool size. The rates of total and mRNA synthesis are expressed in percentages of the young untreated rats and compared to old untreated animals. The effects of PHA-P was studied at 4, 10, 20 and 44 h after its injection. A considerable increase of the total RNA content of the brain cortex was measured during the first 10 h of the experiment followed by a slow decrease. However, the RNA content of the brain cortex was still significantly higher at the end of experiment compared to untreated old rats. The rate of total RNA synthesis increased significantly during the first 10 h and remained constantly high until 44 h. The rate of mRNA synthesis increased to a higher extent than that of the total RNA, and also remained high until 44 h.

beta-Adrenergic responsiveness of human peripheral lymphocytes after mitogenic transformation with phytohemagglutinin

In vitro transformation of human peripheral blood lymphocytes with the mitogen phytohemagglutinin did not alter the total number of beta-adrenergic binding sites for (+/-)-125iodocyanopindolol on the surface of intact cells, whereas binding to membrane fragments of transformed cells appeared to be diminished. In isolated membranes, there was also a marked decrease in basal, fluoride- and hormone-stimulated adenylate cyclase activity after phytohemagglutinin treatment. In whole cells, however, a lowering effect of phytohemagglutinin on levels of cyclic adenosine 3',5'-monophosphate was not apparent. The discrepancy between data on intact and broken cells indicates that the transformed cells do not acquire additional beta-adrenergic receptors or catalytic adenylate cyclase as their cell surface expands due to blastogenesis. It is therefore concluded that mitogenic transformation of human peripheral lymphocytes does not cause specific changes in the beta-adrenergic/adenylate cyclase system.

Interaction of monomeric and oligomeric soybean agglutinins with pig lymphocytes and plasma membranes

The pig lymphocyte surface contains two distinct receptor classes for monomeric (nonmitogen) and oligomeric (mitogen) soybean agglutinins. The major class (70-80%) for which both forms compete effectively binds them with a similar weak avidity in a non-cooperative monovalent reaction. This class appears to be one or more plasma membrane glycolipids and not involved in the mitogenic process. The minor class (20-30%) binds the monomer weakly and non-cooperatively. It binds the oligomers strongly via positively cooperative interactions involving mobile surface molecules in a metabolically energy-independent clustering process. The minor class appears to be one or more of seven plasma-membrane glycopolypeptides. The monomer does not compete effectively for this class nor does it specifically inhibit the mitogenicity of the oligomers, suggesting that receptors involved in the mitogenic process fall into the minor class and are likely to be glycopolypeptides.

Grafting of triggering site onto lymphocytes; distribution of grafted dinitrophenyl groups on cell surface glycoproteins and glycolipids

Quantitative investigation of membrane-bound sialoglycoconjugates on lymphocyte surface was performed by chemical modification of the sialic acid residues with radioactive N4-dinitrophenyl-L-2,4-diaminobutyric acid hydrazide (DNP-DABH). This labeled both glycoproteins and glycolipids with concomitant preservation of the mitogenic activity by multivalent hapten binding protein (anti-DNP antibody). Under conditions where maximum stimulation of thymocytes occurred radioactive DNP-DABH labeled 1.1 X 10(7) glycolipids molecules/cell but, only 3 X 10(6) glycoproteins molecules/cell. When B lymphocytes, which do not undergo DNP-mediated stimulation were used, glycolipids labeling could not be detected. Major differences between stimulation committed and non-committed DNP-modified lymphocytes was the amount of ligand attached to the cell surface sialoglycolipids (gangliosides).

Beta-endorphin modulates human immune activity via non-opiate receptor mechanisms

Here we report that Beta-endorphin is a potent and efficacious suppressor of phytohemagglutinin induced T-lymphocyte blastogenesis when human leukocytes are exposed early in the course of mitogenic activation. This suppression becomes more difficult to observe, however, if blastogenesis is established by prior exposure to mitogen. Suppression by Beta-endorphin is not blocked by pretreatment with the opiate antagonist naloxone. These results, therefore, suggest that neuroendocrine modulation of human immune expression may be a peripheral physiological function of Beta-endorphin which is mediated by mechanisms distinct from traditional opiate receptors.

Changes in membrane fluidity associated with lymphocyte stimulation by succinyl-concanavalin A

Time-resolved fluorescence anisotropy studies of human peripheral blood lymphocytes labeled with 1,6-diphenyl-1,3,5-hexatriene were carried out at temperatures between 4 and 38 degrees C. For unstimulated freshly-isolated lymphocytes the calculated order parameters were found to be 0.62 at 4 degrees C and 0.44 at 37 degrees C. Mitogen-induced alterations in the order parameter were evident within minutes after addition of succinyl-concanavalin A to the cells, increasing to a value of 0.56 after 2 h at 37 degrees C. Both stimulated and unstimulated cells show a decrease in fluorescence anisotropy over the next 2-3 days of culture and after the third day the time-resolved fluorescence anisotropy decay profiles of the two populations of cells were indistinguishable. Our results indicate that there are both short- and long-term changes in the membranes of the cell upon stimulation by mitogen.

Early electrochemical events in lectin-lymphocyte interaction. I. Mechanism of lectin-mediated changes in the electrophoretic mobility of lymphocytes

Concanavalin A, at extremely low concentrations, will produce significant increases in the electrophoretic mobility of murine splenic T lymphocytes. It has been established that the alteration in cellular surface charge is mediated by a factor produced by those lymphocytes that have reacted directly with con A. We originally conjectured that the mobility change might be the consequence of an alteration in the distribution of the charged moieties of membrane glycoproteins. The results of experiments conducted at low temperature raise some questions about this mechanism. Further experiments have been performed to establish the nature of the physicochemical alterations in the peripheral zone of the factor-stimulated lymphocytes that are manifest as changes in cellular surface charge. The results of these studies indicate that, subsequent to the interaction of T lymphocytes with con A, there is a reduction in the number of positively charged amino groups effective at the electrophoretic surface of the cells.

Abrogation of suppressor cell function by inhibitors of prostaglandin synthesis

The weekly intraperitoneal injection of rat erythrocytes into mice induces both a stable autoimmune state, as judged by the appearance of anti-mouse erythrocyte autoantibody and suppressor T cells capable of regulating this response; the latter being demonstrable only in a subsequent transfer system. This autoimmune response and the parallel anti-rat erythrocyte response were both insensitive to exogenous prostaglandin E2 (PGE2). The administration of prostaglandin synthetase inhibitors (indomethacin or aspirin) to mice undergoing immunization with rat erythrocytes had no effect on the anti-rat response, yet mildly exacerbated the onset of the autoimmune state and potently inhibited the generation of suppressor cells. Furthermore the administration of these drugs to recipients of suppressor cells virtually abrogated suppressor cell activity. These observations imply that both the generation and effector function of these suppressor cells may be modulated by prostaglandin synthetase inhibitors while at the same time T helper and B cell functions remain unimpaired.

Separation and localization on sodium dodecyl sulfate polyacrylamide gels of pig spleen lymphocyte plasma membrane proteins which bind 125I-labelled phytohemagglutinin

The protein constituents of splenic pig lymphocytes derived from the plasma membranes, the endoplasmic reticulum or from a non-ionic (Nonidet P-40) detergent of whole cells have been separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis, under reducing and non-reducing conditions. The binding of Phaseolus vulgaris (red kidney bean) phytohemagglutinin to these constituents has been studied by incubation of the labelled lectin with the undried electrophoretograms. Results show characteristic phytohemagglutinin-reactive components in each cell fraction, although the majority of the lectin-binding bands are common to the three fractions. Comparison of binding patterns for the reduced and non-reduced electrophoretograms does not reveal significant differences between the binding profiles. The components which bind the lectin in the largest amounts are located in the upper halves of the gels, which correspond to a molecular range of (75-250) . 10(3) daltons. Our data suggest that pig spleen lymphocyte plasma membranes contain at least 25-30 glycoproteins which can bind phytohemagglutinin. Iodine-labelled phytohemagglutinin binds to the vesicles prepared from lymphocyte plasma membranes and the Scatchard plot shows a non-linear upward concave curve.

Suppression of B-memory cell function by polyclonal lymphocyte activators

When various polyclonal lymphocyte activators (PLA), such as the capsular polysaccharide of Klebsiella pneumoniae (CPS-K), E. coli lipopolysaccharide (LPS), concanavalin A (Con A), dextran sulfate (DS), phytohemagglutinin (PHA), and pokeweed mitogen (PWM) were injected into mice primed with sheep red blood cells (SRBC), anti-SRBC secondary plaque-forming cell (PFC) responses in vitro of their spleen cells to SRBC and to polyclonal B cell activatory (PBA) were more or less decreased. The decrease in the responsiveness was accompanied by the decrease in the number of SRBC-specific rosette-forming cells (RFC) of B-cell type (B memory cells). This resulted neither from emigration of RFC out of the spleen, nor from change of RFC to antibody-forming cells. Further, we revealed that the decreased responsiveness occurs exclusively in the B cell-rich fraction of the spleen cells from PLA-treated SRBC-primed mice, but not in their T cell-rich fraction. It is concluded therefore that PLA exhibited a common action to reduce selectively B-memory cell function by decreasing the number of B memory cells without differentiation to their end cells, although the strength of the action of various PLA varied.

Affinity chromatography of cells and cell membranes

This article attempts to introduce the concept of cellular affinity chromatography as it departs from molecular affinity chromatography. Special emphasis is placed on the selectio of a solid support as well as on the role of lectins as affinity ligands. Our major goal was to bring to light the basic principles involved, multiple options of ligands and matrices, and different techniques, which may be applied to separate the complex cell population as well as cell membranes. It is hoped that further developments in the field, especially in the selection of proper experimental conditions, ligands and matrix material may provide better results. We have tried to identify some of the potential problems which should be considered before these approaches can be used on a routine basis. Although the review deals primarily with the affinity chromatography of cells and cell membranes, examples are presented for diverse systems such as cell organelles, viruses and phages. A table summarizing the use of cellular affinity chromatography is included. It lists more than 80 examples covering the literature up to December, 1979.

Modulation of mitogenic responsiveness by staphylococcal peptidoglycan

Staphylococcal peptidoglycan can modulate in vivo and in vitro antibody responses and is a B-cell mitogen. The effect of in vivo peptidoglycan treatment on the subsequent in vitro mitogenic responsiveness of mouse splenocytes to phytohemagglutinin, concanavalin A, pokeweed mitogen, and lipopolysaccharide was studied by measuring changes in deoxyribonucleic acid synthesis. Injection of peptidoglycan caused a 100% increase in responsiveness to phytohemagglutinin and pokeweed mitogen and a 45% increase in responsiveness to concanavalin A. Responsiveness to lipopolysaccharide was decreased by 40%. Increased phytohemagglutinin and decreased lipopolysaccharide responses were not due to changes in the kinetics of the response or optimal concentrations of these mitogens. Increased responsiveness to phytohemagglutinin lasted for 2 weeks after peptidoglycan injection. Neither increased background deoxyribonucleic acid synthesis nor changes in the proportion of T cells after peptidoglycan treatment fully accounted for the changes in responsiveness to the mitogens. In vitro costimulation with peptidoglycan and phytohemagglutinin, lipopolysaccharide, concanavalin A, or pokeweed mitogen resulted in interference of the response. Cell separation experiments indicated that peptidoglycan-induced modulation of mitogenic responsiveness was mediated by B lymphocytes.

The induction of suppressor T cells by concanavalin A is independent of cellular proliferation and protein synthesis

Factors that govern the induction of suppressor T cells after stimulation with concanavalin A (Con A) were investigated in a two-stage culture system. Normal mouse spleen cells were incubated with Con A in the presence of a variety of drugs and then assayed for suppressive activity by means of a secondary anti-sheep erythrocyte response in vitro. The inclusion of inhibitors of mitosis (vinblastine sulphate or mytomycin C) or protein synthesis (cycloheximide or pactamycin) into normal spleen cell cultures containing Con A failed to inhibit the subsequent development of suppressor cells. Furthermore, spleen cells from mice previously irradiated with 900 rad or injected with cyclophosphamide expressed a level of suppressor activity after Con A stimulation which was equivalent to that of normal spleen cells. However, the inclusion of drugs that inhibit microtubule or microfilament function (colchicine or cytocholasin B) did prevent suppressor cell induction. Kinetic studies also revealed that significant suppressor activity was detectable in normal spleen cells after only 3 h exposure to Con A. These results indicate that the induction of suppressor T cells in this system is a maturation event involving changes in the cell membrane and is entirely independent of protein synthesis and cellular proliferation.

Candidacidal activity of mouse macrophages in vitro

Mouse peritoneal macrophages were infected in vitro with Candida albicans, and the phagocytic and candidacidal activities were estimated by microscopic examination of Giemsa-stained cells. Activated macrophages obtained from either BCG-vaccinated animals or by in vitro exposure of normal macrophages to phytohemagglutinin-induced lymphokines exhibited higher phagocytic and candidacidal activities than did normal macrophages. However, activated macrophages obtained by in vitro exposure of macrophages to candida-induced lymphokines exhibited the highest phagocytic and candidacidal activities. The incorporation of immune mouse serum into the culture medium also enhanced the phagocytic and candidacidal activities of the normal macrophages but failed to improve the function of the activated macrophages. These results suggest that both activated macrophages and antibodies may be required for controlling candida infections in mice.

Membrane dynamics of Friend leukaemic cells. I. Changes associated with cell growth

The relationship between membrane dynamics and cellular growth of Friend leukaemic cells (FLC) was studied by fluorescence polarization (P) using diphenyl hexatriene (DPH). The P-value changes as a function of the state of the cells being maximum in the growing state. The P-value is also influenced by serum concentration and this effect appears to be a passive process.

Characterization of human lymphocyte surface receptors for mitogenic and non-mitogenic substances

To compare the receptor patterns for mitogenic and non-mitogenic substances, surface glycoproteins of human lymphocytes were labelled with the lactoperioxidase-catalysed iodination technique and with a galactose oxidase-tritiated sodium borohydride technique. Labelled cells were detergent-solubilized, and the lysates were allowed to react with insolubilized purified mitogenic lectins, phytohaemagglutinin, leucoagglutinin and an insolubilized non-mitogenic lectin, oxidized leucoagglutinin. Lectin-reactive proteins were eluted with sodium dodecyl sulphate (SDS) buffer. Cell membrane components reactive with anti-lymphocyte globulin (ALG) were retrieved by indirect immunoprecipitation with protein-A-bearing staphylococcus Cowan I strain (SaCI). Lectin- and ALG-reactive proteins were analysed by SDS polyacrylamide gel electrophoresis. Iodinated glycoproteins regularly showed four major components with molecular weights of 120,000, 70,000, 60,000 and 43,000 daltons, respectively, on 7% gels. An additional broad peak in the molecular weight range 20,000--35,000 daltons was found on 10% gels. Tritiated glycoproteins also showed four major components with MW 120,000, 70,000, 60,000 AND 42,000, RESPECTIVely, which reacted with lectin and ALG. In addition, ALG reacted with some glycoproteins with MW between 150,000 and 230,000 daltons. On 10% gels additional lectin- and ALG-binding glycoproteins with MW around 30,000 daltons were found. The similarity in structures bound by mitogenic and non-mitogenic substances indicates that lymphocyte activation may depend on some property conferred by the mitogen.