Enhanced Rosette Formation Research Articles

Blood groups and malaria: fresh insights into pathogenesis and identification of targets for intervention

This review summarizes recent advances in our understanding of the interaction between malaria parasites and blood group antigens and discusses how the knowledge gleaned can be used to target the development of new antimalarial treatments and vaccines. Studies of the interaction between Plasmodium vivax and the Duffy antigen provide the clearest example of the potential for basic research on blood groups and malaria to be translated into a vaccine that could have a major impact on global health. Progress is also being made in understanding the effects of other blood group antigens on malaria. After years of controversy, the effect of ABO blood groups on falciparum malaria has been clarified, with the non-O blood groups emerging as significant risk factors for life-threatening malaria, through the mechanism of enhanced rosette formation. The Knops blood group system may also influence malaria susceptibility, although conflicting results from different countries mean that further research is required. Unanswered questions remain about the interactions between malaria parasites and other blood group antigens, including the Gerbich, MNS and Rhesus systems. The interplay between malaria parasites and blood group antigens remains a fascinating subject with potential to contribute to the development of new interventions to reduce the global burden of malaria.

Environmental Factors Affecting Rosette Formation of Elatum Hybrids of Delphinium

To determine environmental factors involved in rosette formation of Elatum hybrids of Delphinium, bolting behavior in response to temperatures, photoperiods, and light intensities was investigated. Seedlings rosetted under a natural 10-12 hr photoperiod during winter at 22°C. Seedlings subjected to 25/20°C (day/night) for 40 days just after germination formed rosettes after they were transferred to below 20/15°C, whereas they bolted quickly when they were kept at the continuously high temperature. A high percentage of seedlings bolted when they were transferred to a greenhouse kept above 18°C in early October, but those kept at a minimum temperature of 10°C formed rosettes. This rosette formation was also accelerated by exposing seedlings to 50% shading. We conclude that short days induce rosette formation in Elatum hybrids of Delphinium and that cool temperature accelerated it. Exposure of seedlings to high temperatures during the early seedling stage and/or low light intensity after planting also enhanced rosette formation.

Expression of adhesion molecules in endothelial cells-implication of diabetic vascular dysfunction

Ling Zhi-8 (LZ-8), a novel immunomodulatory protein, markedly enhanced the expression of CDllb, but not CDlla, CD13, CD14, CD18, CD33 or HLA-DR, on the U937 cell line in a dose-dependent fashion. It also induced ICAM-1 expression on vascular endothelial cells and significantly augmented γ -interferon-induced cellular binding between vascular endothelial cells and U937. Furthermore, LZ-8 increased the expression of CD2, but not VLA4, VLA5 or LFA3, on MOLT4 and enhanced rosette formation between human T cells and sheep red blood cells. These data suggest that LZ-8 exerts its pharmacological effect by modulating adhesion molecules on immunocompetent cells.

An immunomodulatory protein, ling ZHI-8, facilitates cellular interaction through modulation of adhesion molecules

Ling Zhi-8 (LZ-8), a novel immunomodulatory protein, markedly enhanced the expression of CD11b, but not CD11a, CD13, CD14, CD18, CD33 or HLA-DR, on the U937 cell line in a dose-dependent fashion. It also induced ICAM-1 expression on vascular endothelial cells and significantly augmented gamma - interferon-induced cellular binding between vascular endothelial cells and U937. Furthermore, LZ-8 increased the expression of CD2, but not VLA4, VLA5 or LFA3, on MOLT4 and enhanced rosette formation between human T cells and sheep red blood cells. These data suggest that LZ-8 exerts its pharmacological effect by modulating adhesion molecules on immunocompetent cells.

PMN-derived proteases enhance the affinity of Fcγ receptor II on myeloid cells, but not on B cells

Treatment of monocytes or K562 cells with proteolytic enzymes like pronase or trypsin, increases both the affinity of the type II Fc receptor for IgG and the signaling via this receptor. In the present study we evaluated whether other proteases could similarly enhance Fcγ RII affinity. We furthermore assessed whether all cell types expressing Fcγ RII display this effect. Therefore, proteins from the coagulation system and PMN-derived enzymes were tested for effects on Fcγ RII-mediated ligand binding. Enzymes of the coagulation system were tested both in fibrinogen-depleted plasma, as well as in purified form. No effects were found on Fcγ RII-mediated rosette formation for both situations. In contrast, supernatant of stimulated granulocytes as well as leucocyte elastase were observed to be active in augmenting EA-hIgG rosette formation of thrombocytes and myeloid cell lines K562 and U937. The B cell lines Raji and Daudi, did not show enhanced rosette formation after enzyme treatment. The active component from granulocyte supernatant was partially characterized as a serine esterase with an apparent Mw of 30 kD. We tested whether the isotype specificity of Fcγ RII on K562 cells changes upon enzyme treatment. It was found that all three tested murine subclasses γ 1, γ 2a, γ 2b, bound equally well to this receptor, and interaction with all isotypes was enhanced to the same extent.

Expression of a binding structure for sialic acid-containing glycoconjugates on rat bone marrow-derived macrophages and its modulation by IFN, TNF-alpha, and dexamethasone.

Rat macrophages express a binding structure for sialic acid-containing glycoconjugates (sialic acid-binding receptor, SAR) which can be detected by a rosette assay utilizing SRBC coated with bovine brain gangliosides (E-G). Freshly isolated rat bone marrow cells (BMC) contain about 5% SAR-positive cells. Rat BMC cultured for 1 wk with tissue culture media containing CSF-1 differentiate into a virtually pure population of bone marrow-derived macrophages (BMDM phi). All BMDM phi bound E-G coated with an optimal concentration of gangliosides (100 micrograms/ml). When BMC were cultured for 1 wk with murine recombinant granulocyte-macrophage CSF, irrespective of the dose of GM-CSF, approximately 90% of the cells were identified as rat macrophages, and practically all expressed SAR. Only about 50% of BMDM phi bound SRBC coated with a suboptimal concentration of gangliosides (20 micrograms/ml). However, this percentage increased markedly after 8 to 72 h incubation with 1 to 10,000 U/ml purified murine IFN-alpha or IFN-beta, whereas murine or rat rIFN-gamma at doses above 10 U/ml led to a decrease of E-G binding. Human and murine rTNF-alpha enhanced rosette formation in a dose-dependent manner. These effects could be blocked by the respective anti-cytokine antibodies. Treatment of BMDM phi with dexamethasone also augmented E-G rosetting. The enhancement of E-G binding was abolished by pretreatment of BMDM phi with cycloheximide and actinomycin D but not with mitomycin C, suggesting that de novo synthesis of protein and RNA, but not DNA, is required. Our results demonstrate that all rat BMDM phi constitutively bear SAR, and that murine IFN-alpha, IFN-beta, and TNF-alpha, as well as dexamethasone, may augment SAR expression.

Role of the cytoskeleton in the Fc receptor activity of rat peritoneal macrophages.

High concentration of cytochalasin B (CB) and vinblastine (Vb) inhibited the erythrocyte-antibody (EA) rosette formation of rat peritoneal macrophages (PM). Low concentration of Vb enhanced rosette formation. CB and Vb had the same effect on the rosette formation when anti-SRBC immunoglobulin (Ig) had been previously bound in vivo or in vitro to the Fc receptors (FcR) of the macrophages, suggesting that the intact function of the cytoskeleton is required for the last step of rosette formation. CB and Vb exert a reversible effect on FcR activity. Regeneration of FcR activity was observed also in the presence of 10 microgram/ml cycloheximide. The effect of CB and Vb on rosette formation depends both on the (sub)classes of antibody involved and on the nature of the particulate antigen. Rosettes with living trypanosomes displayed an extremely high CB sensitivity.

Monosaccharide inhibition of E-rosette formation

The capacity of various monosaccharides in solution to block the attachment of sheep red blood cells to human lymphocytes to form E rosettes was assessed. d- or l-Mannose in a concentration of 50 ng/ml reversibly reduced E-rosette numbers by more than one-half: other saccharides were less effective or did not at all inhibit. Neuraminidase treatment of either red cells or lymphocytes enhanced rosette formation. Dextran also enhanced rosette formation, whereas mannan or galactan showed no effect. Treatment of lymphocytes with low concentrations of trypsin or glutaraldehyde completely abolished E-rosette formation; similarly treated sheep red cells could enter into rosette formation. Sheep red blood cells obtained from the same commercial supplier, but from different sheep, exhibited consistent, sometimes marked, differences in susceptibility to oligosaccharide inhibition of E-rosette formation. These data suggest that mannose-like determinants on trypsin-sensitive lymphocyte surface components interact with other carbohydrate determinants on the surface of red cells to form rosettes. Although specific surface glycosyl transferases may be implicated in this adherence, it is possible that nonspecific conformational reactions between carbohydrates may mediate rosette formation.

Biochemical and enzymatic modulation of the Fc receptor on a murine lymphoblastoid cell line

The effect of agents which alter the intracellular levels of cGMP as well as the enzymatic susceptibility of the Fc receptor on a murine lymphoblastoid cell line have been investigated. Incubation with dibutyryl cGMP showed an immediate increase in receptor activity. Imidazole, acetylcholine, and poly(I-C) also enhanced rosette formation but these effects were not evident until 24 hr. The Fc receptor has also been demonstrated to be sensitive to high concentrations of proteases which result in loss of receptor activity. Lower concentrations of proteases, however, as well as neuraminidase, enhanced rosette formation. Incubation with phospholipase A significantly reduced receptor activity while neither phospholipase C nor D had any effect on receptor expression.

A comparative study of procedures for sheep erythrocyte-human-T-lymphocyte rosette formation

A comparative study of several published methods for sheep red blood cell-T-lymphocyte rosette formation was performed. Maximum SRBC-rosette formation occurred with AET treated SRBC in medium supplemented with 20% FCS or with untreated SRBC in 100% FCS. Prolongation of the 4°C incubation period from 4 to 18 h enhanced rosette formation. Fluorescein diacetate staining significantly increased calculated percentage of rosette formation. Fluorescein diacetate staining significantly increased calculated percentage of rosette-forming lymphocytes by allowing accurate indentification of the central lymphocytes in morulas.

Effects of thiols on sheep erythrocytes resulting in enhanced rosette formation with human T lymphocytes.

SummaryThe mechanism of enhanced interaction of T-L with SRBC-A has been explored and the following results obtained: (1) Compared with SRBC, SRBC-A contain identical quantities of protein, phos-pholipid, and sialic acid, but have slightly reduced SH content; (2) treatment of SRBC with thiols having charge properties different from AET also facilitates rosetting; (3) exposure of SRBC to various SH-alkylating reagents, either before or after thiol treatment, does not diminish thiol-enhanced rosetting; (4) trypsinization of SRBC and of SRBC-A completely abolishes the ability of these cells to rosette; and (5) no differences could be detected between intact SRBC and SRBC-A, or in their solubilized membrane components, by SDS-PAGE and by ESR. These results indicate that free SH groups of SRBC membranes are not directly involved in the rosetting process. Thiol-enhanced rosetting probably results from cleavage of membrane S-S bridges resulting in configu-rational changes within the SRBC membrane. The interactio...

Modulation of human T lymphocyte rosette formation by autonomic agonists and cyclic nucleotides

Early rosette formation by T lymphocytes appears to be modulated by cyclic nucleotides. Dibutyryl cyclic 3′,5′ adenosine monophosphate (cyclic AMP) 10 −2 M inhibited E rosette formation up to 83%, while 10 −6 M 8-bromo-cyclic guanosine monophosphate (cyclic GMP) increased rosette formation maximally to 67.4% with less pronounced effect at increased concentrations. T lymphocyte receptors for beta adrenergic, alpha adrenergic, and muscarinic cholinergic agonists appear to influence rosette formation. Isoproterenol 10 −2 M induced 67.3% inhibition, while phenylephrine 10 −5 M and carbamylcholine 10 −4 M were associated with enhanced rosette formation of 67.2% and 57.8%, respectively. Selective blockade with propranolol, phentolamine, and atropine indicated the presence of separate receptor sites. The lack of effect of histamine at concentrations of 10 −3 M and above suggests the absence of specific receptors on peripheral human T lymphocytes.