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New strategies for immunonutritional support include administration of special nutrients such as glutamine. Glutamine is important in several key metabolic processes of immune cells and enterocytes. Exogenous glutamine augments the functions of lymphocytes and macrophages. Neutrophils also reportedly utilize glutamine at a significant rate. Our recent studies demonstrated that glutamine enhances neutrophil function. This article focuses on the effects of glutamine on neutrophil function in surgical stress. Enteral glutamine administration enhanced peritoneal and hepatic bacterial clearance in our rat peritonitis model. Furthermore, IV glutamine supplementation improved the outcome of animals with severe surgical stress. Our in vitro study revealed that supplemental glutamine augmented the bacterial killing function of neutrophils from postoperative patients. Glutamine increased phagocytosis of the neutrophils. In addition, glutamine dose-dependently increased production of reactive oxygen intermediates (ROI) by neutrophils. Thus, our studies suggest that glutamine supplementation may improve bactericidal function of neutrophils by increasing both phagocytosis and ROI production. In conclusion, glutamine plays an important role in neutrophil function. Glutamine may be useful for the prevention, and treatment, of severe infection in critical illness and trauma.

To examine the effects of dietary glutamine on lymphocyte function, male mice aged 6 wk were fed for 2 wk one of three isonitrogenous, isocaloric diets, which varied in glutamine concentration. The control diet included 200 g casein/kg, providing 19.6 g glutamine/kg; the glutamine-enriched diet provided 54.8 g glutamine/kg partly at the expense of casein; and the alanine + glycine-enriched diet provided 13.3 g glutamine/kg. The plasma concentrations of a number of amino acids varied because of the diet fed. The plasma glycine concentration was greater in mice fed the alanine + glycine-enriched diet (380 +/- 22 micromol/L) than in mice fed the control (177 +/- 17 micromol/L) or the glutamine-enriched (115 +/- 18 micromol/L) diets. The plasma glutamine concentration was greater in mice fed the glutamine-enriched diet (945 +/- 117 micromol/L) than in those fed the diet enriched with alanine + glycine (561 +/- 127 micromol/L), but was not different from that in mice fed the control diet (791 +/- 35 micromol/L). There was a significant linear relationship between the amount of glutamine in the diet and plasma glutamine concentration (r = 0.655, P = 0.015). Plasma alanine concentration was unaffected by diet. The reason for the lack of effect of increasing the amount of alanine in the diet upon its concentration in the circulation may relate to its use by the liver. Thymidine incorporation (56 +/- 18 kBq/well versus <10 kBq/well), expression of the alpha-subunit of the interleukin-2 receptor (62 versus 30% receptor positive cells) and interleukin-2 production [189 +/- 28 versus 106 +/- 5 (control) or 61 +/- 13 (alanine + glycine enriched) ng/L] were greater for concanavalin A-stimulated spleen lymphocytes from mice fed the glutamine-enriched diet compared to those from mice fed the other two diets. Thus, increasing the amount of glutamine in the murine diet enhances the ability of T lymphocytes to respond to mitogenic stimulation. Taken together, these observations suggest that increasing the oral availability of glutamine could promote the T-cell driven, cell-mediated immune response.

There is a high incidence of infections in athletes undergoing intense, prolonged training or participating in endurance races (e.g., the marathon), in particular, upper respiratory tract infections. Prolonged, exhaustive exercise can lower the plasma level of the amino acid, glutamine, which is an important fuel for some cells of the immune system and may have specific immunostimulatory effects. This could therefore be an important factor in the event of an impaired response of immune cells to opportunistic infections. The effects of feeding glutamine to sedentary individuals and to marathon and ultramarathon runners before and after prolonged, exhaustive exercise has been investigated in a series of studies that monitored the incidence of infections and some acute-phase response markers. Oral glutamine, compared with a placebo, appeared to have a beneficial effect on the incidence of infections reported by runners after a marathon.

Glutamine has been the point of interest of many nutritional studies concerning parenteral and enteral nutrition. Advantages from glutamine support have been observed previously in animal models. It was shown that glutamine is the energy source for rapidly dividing cells e.g. immune cells, gut mucosa. Recent molecular and protein chemistry studies have begun to define metabolic mechanism of glutamine action, and clinical trials suggest its safe and positive influence on catabolic patients. Parenteral and enteral nutrition enriched with glutamine improves gut integrity and function, decreases infection rate and improves function of immune cells. However, the indications for glutamine enriched nutrition and appropriate protocol of administration need determination. Taken together the data suggest that this amino-acid is an important dietary nutrient and is probably conditionally essential in certain catabolic conditions.

Two closely-related molecules, DR(alpha,beta1*0101) and DR(alpha,beta1*0103), whose beta chains only differ by three amino acids at positions 67, 70, and 71, and six intermediate molecules obtained by site-directed mutagenesis were used to ascertain the respective roles of the three polymorphic residues. Substitutions at positions 70 (D-->Q), 71 (E-->R) and 67 (I or L-->F) strongly affected HA 306-318-specific T-cell recognition. The consequences of the substitution of residue 67 by a phenylalanine depended on the modified HLA-DR molecule. Although this substitution completely inhibited peptide-specific DR1-restricted T-cell recognition, its manifestations on the DR103-restricted T-cell response were variable (abolishing proliferation of some cell lines and not others), no matter what the peptide presented was (HA 306-319 or HIV P25 peptides). We also observed that inhibition of the proliferation of an alloreactive anti-DR103 T-cell clone, caused by a substitution at position 70, was completely cancelled by substitution of residue 67 by a phenylalanine. The observations based on functional experiments, thus, suggest that residue 67 plays an important role in determining conformation of the peptide presented to the T cells. Molecular modeling was used to predict changes induced by amino acid substitutions and highly supports functional data. Substitution of residue 67 by a phenylalanine could have repercussions on the structure of HLA-DR molecule/peptide complexes and affect T-cell recognition.

The main pathway for transmitter glutamate turnover in excitatory synapses is thought to involve an uptake in glial processes, a conversion into glutamine, which recycles to the presynaptic terminal to serve as the main precursor for new synthesis of glutamate. To investigate whether the mechanisms of glutamine and glutamate turnover are linked with the properties of different glutamate synapses, the distribution of glutamine was studied in two types of glutamate synapse in the lamprey spinal cord using immunogold post-embedding electron microscopy. The synapses examined are formed by primary afferent axons (dorsal column axons), which predominantly exhibit a tonic firing pattern, and by giant reticulospinal axons, which primarily fire in brief bursts. Glial cell processes and postsynaptic dendrites displayed the highest density of glutamine labeling in both types of synapse. The level of glutamine was significantly higher in the glial cell processes surrounding the tonic dorsal column synapses, as compared to those surrounding the reticulospinal synapses. The axoplasmic matrix and presynaptic mitochondria, as well as postsynaptic dendrites, contained similar levels of glutamine labeling in both cases. The glutamate labeling in glial processes was also similar at the two types of synapse, while axoplasmic matrix and presynaptic mitochondria displayed four to six times higher levels in the tonic axons. In conjunction with our previous results, showing a different transport activity in glial processes of the two types of excitatory synapse, the results of the present study suggest that the glial pool of neurotransmitter precursor is linked to the rate of transmitter synthesis and release in adjacent synapses.

A polyglutamine expansion (encoded by a CAG repeat) in specific proteins causes neurodegeneration in Huntington's disease (HD) and four other disorders, by an unknown mechanism thought to involve gain of function or toxicity of the mutated protein. The pathological threshold is 37-40 glutamines in three of these diseases, whereas the corresponding normal proteins contain polymorphic repeats of up to about 35 glutamines. The age of onset of clinical manifestations is inversely correlated to the length of the polyglutamine expansion. Here we report the characterization of a monoclonal antibody that selectively recognizes polyglutamine expansion in the proteins implicated in HD and in spinocerebellar ataxia (SCA) 1 and 3. The intensity of signal depends on the length of the polyglutamine expansion, and the antibody also detects specific pathological proteins expected to contain such expansion, in SCA2 and in autosomal dominant cerebellar ataxia with retinal degeneration, whose genes have not yet been identified.

Our aim was to identify proteins that mediate the uptake and degradation of synaptically released glutamate, focusing on the rat retina with its well-defined glutamatergic pathways. Immunoreactivity against the L-glutamate/L-aspartate transporter (GLAST) is present in Müller cells. Ultrastructurally, even the finest glial processes, particularly those ensheathing identified structures of glutamatergic transmission (rod spherules), are immunoreactive for GLAST. Further light and electron microscopic observations revealed that also retinal astrocytes and pigment epithelial cells are immunoreactive for GLAST. No neuronal or microglial staining was observed. This is in line with uptake of exogenous [3H]glutamate previously localized specifically in Müller cells and pigment epithelium (Ehinger and Falck: Brain Res 33:157-172, 1971). Since endogenous glutamate can only be demonstrated in Müller cells if glutamine synthetase (GS) is inhibited (Pow and Robinson: Neuroscience 60:355-366, 1994), the immunocytochemical localization of GS was determined. GS immunoreactivity was found in all but only those cell types immunoreactive for GLAST. The light and electron microscopic patterns of immunoreactivity were very similar, particularly in the outer plexiform layer. The three cell types containing both GS and GLAST (Müller cells, astrocytes, and retinal pigment epithelium) are related developmentally. In the light of the two references quoted the present data indicate that the proteins mediating retinal uptake and degradation of synaptically released glutamate may be GLAST and GS, respectively, and that they may operate in concert to terminate the neurotransmitter action of glutamate.

In human intestinal malignancy, alterations occur in the expression of mucins defined by the MUC-2 gene. These changes include the unmasking of epitopes in the mucin protein core. In order to probe these modifications associated with mucins of the malignant phenotype, a monoclonal antibody (MAb) was developed against synthetic peptide with a sequence based upon that of the protein core of the MUC-2 mucin. The antibody (designated 996) was shown to recognize a high-molecular-weight glycoprotein from colonic carcinoma tissue. The material reacted uniformly with Concanavalin A but variably with other lectins, indicating heterogeneity in the associated oligosaccharide side chains. The protein core was accessible both to 996 antibody binding and to degradation with proteases. Immunization with the affinity-purified mucin-like material elicited antibodies reactive with both the immunogen and the synthetic peptides, confirming the immunogenic character of protein-core determinants. Epitope mapping studies, using synthetic peptides in solution and synthetic peptides tethered to the heads of plastic pins, indicated that the minimum epitope for the 996 antibody is a tetramer of T G T Q. Antibody interaction with the glutamine (Q) residue was determined to be of major importance in the antigen-antibody reaction. The findings illustrate the characterization of an anti-peptide antibody which may be used to probe alterations in MUC-2 mucin expression associated with human intestinal malignant disease.

Arginine, glutamine, the long chain polyunsaturated omega-3 and omega-6 fatty acids, and, to a lesser extent, ribonucleic acid and the vitamins E, C, and A have pharmacologic effects when given in amounts in excess of what is needed to prevent nutritional deficiency. These effects are exerted primarily via the immune system, and immunoenhancing diets that embody the recently developed principles of nutritional pharmacology have been shown to reduce infectious complications by approximately 75% in surgical patients and hospital stay by more than 20% in surgical patients and patients in the intensive care unit in three independent, prospective, randomized studies, two of which were double-blinded. These findings suggest that specialized diets can be designed that will be of benefit to patients with cancer, atherosclerosis, intestinal diseases, autoimmune diseases, infections, and trauma. However, the interaction of these nutrients in pharmacologic amounts with standard pharmacologic drugs is largely unknown, as are the effects of long-term administration of specialized diets to treat these conditions.

In the present study, splenic dendritic cells (DC) and alveolar macrophages (AM) were pulsed with antigen in vitro and subsequently intratracheally instilled to test whether these cells have the capacity to sensitize T cells in the draining lymph nodes of the lung. The data demonstrate that antigen-pulsed DC, instilled in the bronchoalveolar lumen, induce antigen-specific T cell priming in vivo in the draining lymph nodes. T cell priming is only seen with viable but not with killed antigen-pulsed DC. Amounts as low as 5 x 10(3) to 10 x 10(3) cells can still induce some responsiveness. In addition, it was found that instillation of viable as well as killed pulsed Ia-negative AM also leads to T cell priming, although about 10 times higher numbers of cells had to be used in comparison with DC. The results suggest that DC instilled in the bronchoalveolar lumen present antigen directly to naive T cells, whereas for AM other mechanisms are involved.

The light- and electron microscopic localization of glutamate and glutamine in the rat organ of Corti was studied by means of antisera raised against the respective amino acids coupled to carrier proteins. The light microscopic analysis was performed in semithin sections treated according to the peroxidase-antiperoxidase procedure. The two amino acids were visualized in the same ultrathin sections by use of postembedding immunocytochemistry with two different gold particle sizes. The distribution of aspartate-like immunoreactivity was also recorded, but only at the light microscopic level. In the hair cells, the level of glutamate-like immunoreactivity was higher than that in supporting cells but lower than that in the presumed glutamatergic terminals of cerebellar parallel and mossy fibres. The latter types of terminal were sampled from ultrathin sections that had been incubated under the same conditions as the cochlear sections. Within the hair cells, gold particles signalling glutamate were enriched on mitochondria but not on clusters of synaptic vesicles. Glutamine-like immunoreactivity was present in hair cells as well as supporting cells. The glutamate/glutamine ratio, expressed as the ratio between the respective gold particle densities, was considerably lower for hair cells compared with the cerebellar excitatory terminals. No consistent difference was found between outer and inner hair cells in relation to the levels and subcellular distribution of glutamate and glutamine immunoreactivities. Aspartate-like immunoreactivity was accumulated in outer hair cells, with some labelling also of border cells and Böttcher cells. While the present study confirmed the presence of glutamate in hair cells and demonstrated that these cells are also endowed with the important glutamate precursor glutamine, it revealed notable differences between hair cells and presumed glutamatergic terminals in the CNS. These could reflect differences in the synthesis and compartmentation of transmitter glutamate. Methodological factors could also contribute. Alternatively, the differences could be interpreted to suggest that the hair cell transmitter is not glutamate, but a similar compound. Aspartate could be a candidate in the case of the outer hair cells.

In inbred rats, the antibody response to the known sequential polypeptide (Tyr-Glu-Ala-Gly)n (T-G-A-Gly)n is under the control of two independently assorting loci; (co) dominant, Ag-B-linked Ir-(T-G-A-Gly) I, controlling qualitative responsivenss, and a non-Ag-B-linked modifier locus termed Ir-(T-G-A-Gly) II, controlling the level of antibody produced. The antibody response to (T-G-A-Gly)n was solely IgG and the level of antibody produced was dependent upon Ir-(T-G-A-Gly) II for phenotypic response type.

The offspring of low responder F344 female rats that were immunized with poly(Glu52Lys33Tyr15) aggregated with MeBSA prior to mating showed a higher antibody response to the polypeptide antigen than did the offspring of unimmunized females. Immunization of the mothers with unaggregated polypeptide, or with DNP-BGG, did not affect the antibody response of the offspring even when high doses of antigen were used. When the polypeptide used to immunize the mothers was given as an aggregate, some crossed the placenta to the fetus. The antigen was first detected in the placenta, blood and liver of the fetus at 15 days of gestational age. After birth, it was in the liver and spleen up to 6 weeks af age, and thereafter it was present only in the bone marrow.