SREBP1-induced fatty acid synthesis depletes macrophages antioxidant defences to promote their alternative activation

Macrophages exhibit a spectrum of activation states ranging from classical to alternative activation¹. Alternatively, activated macrophages are involved in diverse pathophysiological processes such as confining tissue parasites², improving insulin sensitivity³ or promoting an immune-tolerant microenvironment that facilitates tumour growth and metastasis⁴. Recently, the metabolic regulation of macrophage function has come into focus as both the classical and alternative activation programmes require specific regulated metabolic reprogramming⁵. While most of the studies regarding immunometabolism have focussed on the catabolic pathways activated to provide energy, little is known about the anabolic pathways mediating macrophage alternative activation. In this study, we show that the anabolic transcription factor sterol regulatory element binding protein 1 (SREBP1) is activated in response to the canonical T helper 2 cell cytokine interleukin-4 to trigger the de novo lipogenesis (DNL) programme, as a necessary step for macrophage alternative activation. Mechanistically, DNL consumes NADPH, partitioning it away from cellular antioxidant defences and raising reactive oxygen species levels. Reactive oxygen species serves as a second messenger, signalling sufficient DNL, and promoting macrophage alternative activation. The pathophysiological relevance of this mechanism is validated by showing that SREBP1/DNL is essential for macrophage alternative activation in vivo in a helminth infection model.

De novo assembly of the complex genome of Nippostrongylus brasiliensis using MinION long reads

BACKGROUND

Eukaryotic genome assembly remains a challenge in part due to the prevalence of complex DNA repeats. This is a particularly acute problem for holocentric nematodes because of the large number of satellite DNA sequences found throughout their genomes. These have been recalcitrant to most genome sequencing methods. At the same time, many nematodes are parasites and some represent a serious threat to human health. There is a pressing need for better molecular characterization of animal and plant parasitic nematodes. The advent of long-read DNA sequencing methods offers the promise of resolving complex genomes.

RESULTS

Using Nippostrongylus brasiliensis as a test case, applying improved base-calling algorithms and assembly methods, we demonstrate the feasibility of de novo genome assembly matching current community standards using only MinION long reads. In doing so, we uncovered an unexpected diversity of very long and complex DNA sequences repeated throughout the N. brasiliensis genome, including massive tandem repeats of tRNA genes.

CONCLUSION

Base-calling and assembly methods have improved sufficiently that de novo genome assembly of large complex genomes is possible using only long reads. The method has the added advantage of preserving haplotypic variants and so has the potential to be used in population analyses.

Genome-wide transcriptomic analysis of intestinal tissue to assess the impact of nutrition and a secondary nematode challenge in lactating rats

Background

Gastrointestinal nematode infection is a major challenge to the health and welfare of mammals. Although mammals eventually acquire immunity to nematodes, this breaks down around parturition, which renders periparturient mammals susceptible to re-infection and an infection source for their offspring. Nutrient supplementation reduces the extent of periparturient parasitism, but the underlying mechanisms remain unclear. Here, we use a genome wide approach to assess the effects of protein supplementation on gene expression in the small intestine of periparturient rats following nematode re-infection.

Methodology/Principal Findings

The use of a rat whole genome expression microarray (Affymetrix Gene 1.0ST) showed significant differential regulation of 91 genes in the small intestine of lactating rats, re-infected with Nippostrongylus brasiliensis compared to controls; affected functions included immune cell trafficking, cell-mediated responses and antigen presentation. Genes with a previously described role in immune response to nematodes, such as mast cell proteases, and intelectin, and others newly associated with nematode expulsion, such as anterior gradient homolog 2 were identified. Protein supplementation resulted in significant differential regulation of 64 genes; affected functions included protein synthesis, cellular function and maintenance. It increased cell metabolism, evident from the high number of non-coding RNA and the increased synthesis of ribosomal proteins. It regulated immune responses, through T-cell activation and proliferation. The up-regulation of transcription factor forkhead box P1 in unsupplemented, parasitised hosts may be indicative of a delayed immune response in these animals.

Conclusions/Significance

This study provides the first evidence for nutritional regulation of genes related to immunity to nematodes at the site of parasitism, during expulsion. Additionally it reveals genes induced following secondary parasite challenge in lactating mammals, not previously associated with parasite expulsion. This work is a first step towards defining disease predisposition, identifying markers for nutritional imbalance and developing sustainable measures for parasite control in domestic mammals.

Contribution of 5-HT2A receptor in nematode infection-induced murine intestinal smooth muscle hypercontractility

BACKGROUND & AIMS

Enteric nematode infection induces a smooth muscle hypercontractility that depends on interleukin (IL)-4 and IL-13 activation of the signal transducer and activator of transcription (STAT) 6. Serotonin (5-HT) is involved in the physiologic regulation of gut function. The present study investigated the contribution of 5-HT and its receptors in nematode-induced intestinal smooth muscle hypercontractility.

METHODS

Mice were infected with Nippostrongylus brasiliensis (N brasiliensis) or Heligmosomoides polygyrus (H polygyrus) or injected intravenously with IL-13. Segments of jejunum were suspended in organ baths, and smooth muscle responses to 5-HT were determined in the presence or absence of specific 5-HT antagonists. IL-4, IL-13, and 5-HT receptor messenger RNA expressions were determined by real-time quantitative polymerase chain reaction.

RESULTS

5-HT evoked a modest contraction of smooth muscle in wild-type (WT) mice that was unaltered by the 5-HT2A antagonist ketanserin. N brasiliensis infection induced a smooth muscle hypercontractility to 5-HT that was abolished by 5-HT(2A) antagonists but not by other 5-HT antagonists. Infection-induced up-regulation of 5-HT2A expression was correlated with the smooth muscle hypercontractility to 5-HT. The infection-induced up-regulation of 5-HT2A in WT mice was observed also in IL-4(-/-) mice but was not seen in IL-13(-/-) or STAT6(-/-) mice. In addition, smooth muscle responses to 5-HT and 5-HT2A expression in WT mice were also enhanced by IL-13 or H polygyrus infection.

CONCLUSIONS

These data show that 5-HT2A is one of the molecules downstream from STAT6 activation that mediates changes in smooth muscle function. 5-HT2A represents a novel therapeutic target for modulating immune-mediated effects on intestinal motility.

Strongyloides ratti infection in the large intestine of wild rats, Rattus norvegicus

The large intestine of a rat has been neglected almost completely as a site of Strongyloides sp. infection. We reported that adult Strongyloides ratti remained in the large intestine for more than 80 days, producing more number of infective larvae than small intestine adults, and therefore hypothesized that parasitism in this site could be a survival strategy. In wild rats, however, no study has focused on large intestine infections of Strongyloides. The present study revealed that 32.4% of 68 wild rats, Rattus norvegicus, had the infection of S. ratti in the large intestine, with an average of 4.7 worms. These worms harbored normal eggs in the uterus. In a laboratory experiment with S. ratti and Wister rats, daily output of infective larvae by 4.7 females in the large intestine was estimated to be 4,638.4, suggesting that a few parasites could play a role in the parasite transmission. Five species of nematode found in the wild rats showed seasonality in infection intensity, with highest intensities in March-May. The number of S. ratti in the large intestine was also highest in these months.

Lactic dehydrogenase virus infection reduces the expulsion of the nematode Nippostrongylus brasiliensis

The interleukin (IL)-13-mediated goblet cell response is the major host effector system involved in the expulsion of Nippostrongylus brasiliensis. Lactic dehydrogenase virus (LDV) induced higher levels of N. brasiliensis egg production compared with controls, but the effect of LDV infection on worm expulsion of, and goblet cell and IL-13 responses to, N. brasiliensis have not been studied. In this study, the effects of LDV infection on these host responses against N. brasiliensis were examined. Mice with chronic LDV infection showed significantly lower worm expulsion rates than non-LDV-infected mice after N. brasiliensis infection, and there were no significant differences in the ratio of female versus male adult worms between control and LDV-infected mice. The number of goblet cells in LDV-infected mice was significantly lower than that in controls. In addition, the levels of IL-13 gene expression in lymph nodes were significantly lower in LDV-infected mice compared with controls. These results suggest that LDV infection reduces the protective immune responses against N. brasiliensis infection by the suppression of IL-13 production.

Concurrent infections with Trypanosoma brucei and Nippostrongylus brasiliensis in mice deficient in inducible nitric oxide

Concurrent infection with Trypanosoma brucei (Tb) delays the normal protective responses of mice to the gastrointestinal parasite Nippostrongylus brasiliensis (Nb). The course of such infections was followed in mice genetically deficient in inducible nitric oxide synthase (INOS) to assess the role of nitric oxide (NO) in this effect. The time course of trypanosome infection in INOS deficient (INOS-/-) mice was similar to that in wild type (WT) and heterozygote (INOS+/-) mice but did not result in NO production. Although concurrent infection with Tb increased initial susceptibility to Nb in INOS-/- mice, the immune-mediated loss of N. brasiliensis and the associated decline in faecal egg output occurred more rapidly then in WT and INOS+/- littermates. Concurrent infection with trypanosomes markedly suppressed Concanavalin A (ConA)-induced in vitro proliferation of splenic lymphocytes in all groups, but had little effect on the responses of mesenteric node lymphocytes. Trypanosome infection was also associated with increased early release of interferon-gamma and reduced IL-5 from lymphocytes stimulated in vitro with ConA, but did not affect later release of IL-5. The overall similarity of proliferative and cytokine responses in WT, INOS+/- and INOS-/- mice suggest that the suppressive effects of T. brucei on N. brasiliensis infection do not simply reflect depressed lymphocyte responsiveness or altered cytokine profiles. NO appears to be involved in suppression only of the later phases of the host responses to Nb.

Immune-mediated damage is not essential for the expulsion of Nippostrongylus brasiliensis adult worms from the small intestine of mice

Nippostrongylus brasiliensis adult worms are expelled from the rat small intestine during a primary infection by two steps. First, host immune responses cause damage to the worms, and then a nonspecific inflammatory response initiates expulsion. We have tested the two-step expulsion hypothesis in mice infected with N. brasiliensis. After a primary infection in C57BL/6 mice, adult worms started to lay eggs on day 5 postinfection (p.i.) and were expelled around day 9-10 p.i. According to the rat system, 5 day- and 8-day-old worms were assumed to be 'normal' and 'damaged', respectively. When 5 day- and 8 day-old worms obtained from C57BL/6 mice were transferred surgically into the small intestine of naive C57BL/6 mice, both 5 day- and 8 day-old worms were almost simultaneously expelled by day 6 postworm implantation (p.w.i.). In contrast, when 5 day- and 8 day-old worms of mouse origin were implanted into naive Wistar rats, 8 day-old worms were expelled by day 5 p.w.i., while 5 day-old worms were expelled by day 8 p.w.i. Similar results were obtained when BALB/c mice were used. Therefore, mice can expel N. brasiliensis adult worms as rapidly as rats expel 'damaged' worms, regardless of the status of the worms ('normal' or 'damaged'). Stat6-deficient mice were unable to expel implanted 5 day-old worms up to day 10 p.w.i., suggesting that cellular mechanisms depending on Stat6-signalling system are necessary for the expulsion. When N. brasiliensis adult worms obtained from Stat6-deficient mice 5 and 15 days after a primary infection were implanted into Wistar rats, the former established in the recipient rats for approximately 1 week and were then expelled by day 10 p.w.i., whereas the latter were expelled by day 4 p.w.i. These results suggest that immune-mediated damage of N. brasiliensis adult worms (first step) is not a prerequisite for expulsion from the small intestine of mice, although adult worms are actually damaged by Stat6-independent immune mechanisms.

Intestinal distribution of worms and host ingesta in Nippostrongylus brasiliensis

The gastrointestinal nematode Nippostrongylus brasiliensis is thought to feed on host ingesta, and it is generally thought that the presence of ingesta determines the distribution of this parasite within the host intestine. However, these assertions have not been supported by direct evidence. The purpose of this study was to test the hypothesis that N. brasiliensis worms are preferentially found in regions of the host small intestine containing ingesta. The relationship between worm and ingesta distribution was investigated using mice infected with N. brasiliensis and killed on day 8 postinfection at 0130, 0730, 1330, or 1930 hr. There was an inverse relationship between worm and ingesta distributions, and the worms were distributed significantly more anteriad in the intestine than host ingesta, at all times during the 24 hr. To determine what the worms fed on, host ingesta, tissue, and blood were differentially labeled with the fluorescent dyes rhodamine B and Fluoresbrite. The results of this study suggest that N. brasiliensis feeds on the host's intestinal wall, and that habitat distribution of this parasite within the small intestine is not directly related to the presence of luminal ingesta.

Trapping and immobilization of Nippostrongylus brasiliensis larvae at the site of inoculation in primary infections of interleukin-5 transgenic mice

Interleukin-5 (IL-5) transgenic mice are highly resistant to primary infections with the intestinal nematode Nippostrongylus brasiliensis; few parasites are found in the intestines of infected animals, and egg production is minimal. While adult worms may be damaged in the intestine, larval migration, development, and viability may also be impaired in other tissues. This study addresses the migration of N. brasiliensis larvae through the skin and lungs and associated cellular responses in primary infections of IL-5 transgenic mice. Although some larvae may have been trapped and killed in the lungs of IL-5 transgenic mice, most apparently failed to reach this site. Two or more hours after infection of IL-5 transgenic mice, eosinophils were a major component of the cellular infiltrate at the subcutaneous site of injection, and localized eosinophil degranulation was extensive. Seventy-five to ninety-five percent of the larvae injected into subcutaneous air pouches in IL-5 transgenic mice were retained there for at least 24 h. In contrast, in nontransgenic mice, less than 20% of larvae could be recovered from the skin 2 or more h postinjection, and eosinophil activity was modest at all times. The data strongly suggest that eosinophils can restrict the movement of N. brasiliensis larvae in the first few hours of a primary infection and that this has profound effects on later stages of parasite development. Preexisting eosinophilia, due either to allergy or to infection with tissue-invasive helminth species, may therefore confer some degree of immediate and nonspecific resistance in primary infections with parasitic worms.

Purification and properties of monomeric (G1) forms of acetylcholinesterase secreted by Nippostrongylus brasiliensis

Acetylcholinesterase (AChE) activity secreted by Nippostrongylus brasiliensis was resolved by sucrose density centrifugation and gel permeation chromatography in single peaks estimated at 4.3 S and 60-85 kDa, respectively. Sedimentation was unaffected by the inclusion of detergent. AChE was purified by affinity chromatography on 9-[Nbeta-(epsilon-aminocaproyl)-beta-aminopropylamino]-acridinium bromide hydrobromide-coupled sepharose 4B. Three forms of the enzyme (A, B and C) were distinguished by non-denaturating polyacrylamide gel electrophoresis, and displayed apparent masses of 74, 69 and 71 kDa respectively when resolved by SDS-PAGE. All three isoforms showed a preference for acetylthiocholine (ASCh) as substrate. They were highly sensitive to inhibition by the AChE-specific inhibitor bis(4-allyldimethylammoniumphenyl)pentan-3-one dibromide, with inhibitor concentration reducing initial activity by 50% (IC50) between 0.1 and 0.8 microM, but activity was unaffected by tetramonoisopropylpyrophosphortetramide (iso-OMPA) at concentrations up to 10 mM. We conclude that the secreted enzymes are authentic AChEs of hydrophilic monomeric (G1) form and broadly similar properties, but which can be distinguished by molecular mass, inhibitor sensitivities and the degree of excess substrate inhibition.

Worm kinetics and serum IgE in hooded lister rats infected with the acanthocephalan Moniliformis moniliformis and the nematode Nippostrongylus brasiliensis

After infection with the intestinal helminths Moniliformis moniliformis or Nippostrongylus brasiliensis, worm-specific IgE first appeared in the serum rats between days 10 and 24 p.i., varying with host age, worm species and worm dose used. The rate of increase in specific IgE was comparable regardless of the worm species, infection dose or host age and a peak response was observed about 1 month after the sera turned positive. In the M. moniliformis infections, these events took place long before the beginning of worm expulsion on day 63 in high-dose (50 worms) infections, and potentiation of heterologous IgE was not observed. In contrast, IgE stimulation by N. brasiliensis infections was detected as potentiation of anti-ovalbumin IgE, anti-M. moniliformis IgE and total IgE. Most of the total IgE in the serum of M. moniliformis-infected rats was likely to be the worm-specific IgE. Anthelminthic removal of M. moniliformis revealed that the presence of residual worms was necessary to maintain worm-specific IgE production.

Dissociation of early and late protective immunity to the nematode Nippostrongylus brasiliensis in Brown Norway and Fischer-344 rats

Worm expulsion of, and IgE and interferon (IFN)-gamma responses to, Nippostrongylus brasiliensis were studied in 2 rat strains, Brown Norway (BN) and Fischer (F)-344. BN rats expelled the majority of worms by day 14 post-infection (p.i.) with approximately 6% of worms surviving for at least 3 weeks. In F-344 rats, worm expulsion was delayed by 2 days relative to that in BN, while the numbers of residual worms were significantly fewer than in BN, suggesting that different immune mechanisms are involved in early and late phases of immunity. Total serum IgE, as well as in vitro IgE production by mesenteric lymph node (MLN) cells, was increased 2 weeks p.i., the levels being markedly higher in BN than in F-344 rats. Serum rat mast cell protease II was also increased more significantly in BN than in F-344 rats. In contrast, production of IgG2a and IFN-gamma by MLN and spleen cells was found to be higher in F-344 than in BN rats. These results indicate that the early worm expulsion is correlated with the host IgE and mast cell responsiveness, whereas the persistence of infection in the late period may be controlled by different immune mechanisms.

Role of T lymphocytes in secretory response to an enteric nematode parasite. Studies in athymic rats

Athymic (nude) rats have been used to assess the role of thymus-dependent T cells in the control of the intestinal response following infection with the enteric parasite, Nippostrongylus brasiliensis. Tissues from infected rats were excised on days 4, 7, 10, and 21 postinfection (p-i) for physiological and morphological studies; uninfected (day 0) rats served as controls. In response to the worm burden, jejunal tissues displayed a secretory response, indicated by an elevated baseline short-circuit current (Isc) on days 7 and 10 p-i, and were more responsive to histamine than control tissues. Despite this enhanced secretory response, approximately 35% of the worm burden was still present on day 21 p-i (compared with expulsion of > 95% by day 14 p-i in normal rats). Mast cell activation and hyperplasia, increased goblet cell (implying increased mucus synthesis) and intraepithelial leukocyte numbers, and abnormalities in Isc responses after electrical stimulation of enteric nerves were identified following infection. These events in nude rats were attenuated or delayed in onset as compared with conventional immunocompetent rats. Our results support the postulate that thymus-dependent T cells regulate the timing and/or nature of the mucosal response to enteric parasitic infections. However, ion secretion was not altered in the absence of T cells and, therefore, is more likely to be a consequence of mast cell activation.

IFN inhibits inflammatory responses and protective immunity in mice infected with the nematode parasite, Nippostrongylus brasiliensis

Mice infected with the gastrointestinal nematode parasite Nippostrongylus brasiliensis (Nb) develop responses associated with enhanced production of IL-4 (increased serum IgE levels and intestinal mucosal mastocytosis) and IL-5 (tissue and peripheral blood eosinophilia). The antagonistic effects of IFN on IL-4-mediated responses prompted an examination of the effects of IFN on the host response to Nb. Treatment with rIFN-alpha and rIFN-gamma induced a marked increase in parasite egg production (fecundity) in BALB/c mice infected with Nb and delayed intestinal expulsion of adult worms. Treatment with rIFN-alpha or rIFN-gamma also inhibited the rise in peripheral blood eosinophilia that follows inoculation with Nb, and the intensity of pulmonary perivascular tissue eosinophilia. However, Nb-induced increases in serum IgG levels and intestinal mastocytosis were only temporarily delayed by IFN. Induction of endogenous IFN production by injection of fixed Brucella abortus into mice infected with Nb also resulted in an increased worm fecundity and delayed adult worm expulsion. These effects were ablated when mice given Brucella abortus also received injections of neutralizing anti-IFN antibodies. Thus, IFN inhibit host protective immunity to Nb, perhaps by interfering with the production and effects of Th2 cytokines.

Dissociation of specific and total IgE antibody responses following repeated low-level infections with Nippostrongylus brasiliensis in rats

IgE, IgG and mast cell responses were studied in rats infected weekly with 10 larvae of Nippostrongylus brasiliensis (NB). Worm recovery at 8 weeks of repeated infections was six-fold greater than that of a single infection with 10 larvae, suggesting the accumulation of worms during the repeated infections. Total serum IgE was increased after 2 weeks of infection, and further increased after repeated infections: at 6 weeks of infection the level was four to six times higher than that after a single infection. Anti-NB IgG1 levels were also significantly higher after repeated infections than after a single infection. On the other hand, there was no significant difference in the level of anti-NB IgE between single and repeated infections, as determined by ELISA, as well as by passive cutaneous anaphylaxis (PCA) reaction. Mastocytosis was induced in the small intestine after both single and repeated infections, but the levels did not differ between the two. These results indicate that total IgE and specific IgG1 production are augmented by repeated helminth infections, but specific IgE and mast cell responses are not. This pattern of response may minimize the development of IgE-dependent hypersensitivity reactions with repeated helminth infections.

Role of T lymphocytes in intestinal mucosal injury. Inflammatory changes in athymic nude rats

To determine the role of T cells versus mast cells in mucosal injury, we documented structural and functional changes in the intestine of congenitally athymic nude rats during infection with the enteric parasite, Nippostrongylus brasiliensis. Studies were conducted at days 4, 7, 10, and 21 postinfection; controls were uninfected. Villus damage was indicated by morphological abnormalities at days 7, 10, and 21 and reduced activities of disaccharidase enzymes at days 10 and 21. The activity of the proliferative enzyme, thymidine kinase, was increased only at day 21, at which time the crypts were elongated. Epithelial permeability increased significantly: 5-hr recovery (in urine and blood) of the probe molecule, [51Cr]EDTA, following injection into ligated jejunal segments, was elevated at days 7 and 10. Uptake of a protein antigen, ovalbumin, from lumen to blood followed a similar pattern. No evidence of functional T cells was demonstrated. However, mucosal mast-cell activation was indicated by elevated serum levels of rat mast-cell protease II at days 7 and 10. We conclude that the absence of thymus-derived T cells does not preclude mucosal damage involving impaired barrier and digestive function. Mucosal mast cells may be involved in causing the injury in this model.

Bromodeoxyuridine labeling studies on the proliferation of intestinal mucosal mast cells in normal and athymic rats

The proliferation of mucosal-type mast cells (MMC) in rat small intestine was studied using a bromodeoxyuridine (BrdU)-labeling method. After 24-h cumulative injections of BrdU into adult SD rats, 3.5% of MMC were labeled, while only 0.3% and 0.1% of mast cells were labeled in back skin and ear respectively. From the results, it was concluded that MMC division occurred more than 10 times as frequently as the division of skin mast cells. Similar results were obtained in athymic adult rats (F344/N Jcl-rnu) in which the number of MMC was similar to that in heterologous animals. Thus, thymic factor(s) or T cells may not have an important role in MMC division in normal states. When SD rats were infected with Nippostrongylus brasiliensis, vigorous proliferation of MMC was brought about 13 to 15 days after infection. At that period, 40% of MMC were labeled by a single injection of BrdU, and 85% of MMC were labeled by 9-h cumulative injections of BrdU, with the result that most MMC rapidly proliferated in the intestinal mucosa during this period. Mitotic figures of MMC were sometimes observed. On the contrary, hyperplasia of MMC was not observed in athymic rats infected with nematodes. Therefore, MMC hyperplasia after nematode infection is dependent on thymic factor or T cells, and its mechanism is different from that of MMC division in normal states, in which thymic factor(s) or T cells are not essential.

Suppression of phytohemagglutinin induced splenocyte proliferation during concurrent infection with Eimeria nieschulzi and Nippostrongylus brasiliensis

Results suggest that infection with Eimeria nieschulzi (Protozoa) interferes with splenocyte proliferation induced by infection with Nippostrongylus brasiliensis (Nematoda).

Hypoalbuminemia in energy-malnourished rats infected with Nippostrongylus brasiliensis (Nematoda)

Rats fed a restricted amount (60% of ad libitum intake) of a well-balanced diet (protein energy:total energy ratio of 0.20) had a reduced growth rate but maintained near-normal plasma albumin concentrations. However, when such animals were infected with Nippostrongylus brasiliensis (a hookwormlike intestinal parasite), plasma albumin values fell precipitously, from a preinfection value of 34.7 g/L to 21.3 g/L on d 10 postinfection (p.i.). The hypoalbuminemia developed rapidly, without changes in body weight and despite an adequate amount of dietary protein. Similarly infected well-nourished animals showed a much less severe effect, plasma albumin values falling from 34.8 to only 31.3 g/L by d 10 p.i. Two measurements of gastrointestinal integrity, [51Cr]albumin leakage from the plasma and intestinal permeability to mono- and disaccharide sugars, suggested that the alterations in plasma albumin values could be explained on the basis of protein leakage into the gastrointestinal tract through parasite-induced lesions. Much greater changes in the indices of mucosal integrity were observed in the undernourished animals and overall it was clear that the energy-restricted animals had been far more severely affected by the parasite than their well-fed counterparts. The results are discussed with reference to the etiology of kwashiorkor in humans.

Origins of serum IgE and of the homocytotropic antibody-secreting cells in the thoracic duct lymph of rats infested with Nippostrongylus brasiliensis

Mesenteric lymphadenectomy caused a marked reduction in the amounts of both parasite-specific and total IgE in the serum of Nippostrongylus brasiliensis infested rats. This was accompanied by reduced quantities of IgE in the thoracic duct lymph, showing that the mesenteric lymph node is of great importance in the generation of the elevated IgE levels which accompany this infestation. Conversely, the intestinal lamina propria and the Peyer's patches did not appear to be significant contributors to either thoracic duct lymph or serum IgE levels. Homocytotropic antibody-secreting cells specific for parasite antigens were detected in the thoracic duct lymph of lymphadenectomized rats and are believed to arise directly from the gut mucosa and possibly from Peyer's patches.