正常妊娠大鼠的Th2型免疫反应

采用流式细胞仪,^3H-TdR掺入和酶联免疫打点(enzyme-linked immunospot,ELISPOT)方法研究妊娠免疫学指标的改变。妊娠晚期大鼠脾脏单个核细胞表面分子主要组织相容性抗原Ⅱ(MHCⅡ)明显下调,外周血单个核细胞表达CD11c明显减少,共激活分子B7-1和B7-2未见改变;脾脏和外周血单个核细胞中Th2细胞因子IL-10、IL-4表达增多,TGFD阳性细胞数也明显增加,而Th1细胞因子IFNγ的产生未受抑制。此外,脾脏和外周血中单个核细胞的抗原特异性增殖未见改变,而腹腔淋巴结细胞的增殖明显升高。脾脏单个核细胞在妊娠晚期分泌较少的抗原特异性抗体。提示妊娠期性激素具有免疫调节作用,可能与怀孕时Th1细胞介导的自身免疫性疾病得到缓解有关。     

Gene activity and the development of early parasitic stages of nematodes

Actinomycin-D, 8 × 10^?6m, blocked the action of the stimulus from the host which normally initiates the development of the infective stage of Haemonchus contortus to the first parasitic stage. However, the action of the stimulus in initiating exaheathment was not affected by the antibiotic.The significance of these results in relation to the activity of the gene set of the first parasitic stage and the control of exsheathment of the infective stage is discussed.     

Recent progress in the development of RNA interference for plant parasitic nematodes

RNA interference (RNAi), first described for Caenorhabditis elegans , has emerged as a powerful gene silencing tool for investigating gene function in a range of organisms. Recent studies have described its application to plant parasitic nematodes. Genes expressed in a range of cell types are silenced when preparasitic juvenile nematodes take up double-stranded (ds)RNA that elicits a systemic RNAi response. Important developments over the last year have shown that in planta expression of a dsRNA targeting a nematode gene can successfully induce silencing in parasitizing nematodes. When the targeted gene has an essential function, a resistance effect is observed paving the way for the potential use of RNAi technology to control plant parasitic nematodes.     

Transglutaminase-catalyzed reactions in the growth, maturation and development of parasitic nematodes

Parasitic nematodes cause several debilitating diseases in humans and animals. New drugs that are parasite specific and minimally toxic to the host are needed to counter these infections effectively. The identification and inhibition of enzymes that are vital for the growth and survival of parasites offer new approaches for developing effective chemotherapeutic agents. Several enzymes in nematodes fall into this category. Here, Ramaswamy Chandrashekar and Kapil Mehta examine in detail the role of transglutaminase, a protein-crosslinking enzyme, in the normal growth and development of nematodes, with an emphasis on filarial parasites.     

Diversity of bacteria associated with grassland soil nematodes of different feeding groups

The bacterial diversity associated with soil nematodes and its relationship with their feeding habits are as yet poorly understood. In the present study the diversity and abundance of bacteria from nematodes and their surrounding soil were analysed and compared. The nematodes were collected from a grassland soil and sorted into bacterial, fungal, plant, predatory and omnivore feeding groups and assigned to taxonomic groups. Total DNA was extracted from the nematodes and partial bacterial 16S rRNA genes were PCR amplified, cloned and sequenced. The abundance and composition of bacterial taxa differed between and within feeding groups. The lowest bacterial diversity was found in the predatory nematodes Prionchulus sp., whereas the highest bacterial diversity was associated with the bacterial-feeding nematode Acrobeles sp. The soil had a more diverse bacterial community than the communities found in the nematode groups. The 16S rRNA gene sequences of bacteria associated with nematodes did not overlap with those detected in soil as determined using the cloning screening approach. However, bacterial sequences identified from nematodes could be detected in the soil with targeted PCR. Our data suggest that the nematodes do not feed on the most abundant bacteria present in soil. Furthermore, several nematodes contained suspected bacterial symbionts and parasites.     

New Lactococcus strain with immunomodulatory activity: enhancement of Th1-type immune response

Few studies exist dealing with the probiotic activity of lactococci, which are commonly used as starter bacteria in the manufacture of many kinds of fermented dairy products. Fifteen strains of the genus Lactococcus were examined for their probiotic activities, such as immunomodulatory effects. Six strains induced the production of cytokines (IL-12, IL-6, and TNF-alpha) in macrophage-like cell line J774.1, and the highest induction was observed with Lactococcus lactis subsp. lactis G50. The cytokine induction in the J774.1 cell line was almost entirely sustained after heat-killing of the strain. Spleen cells from BALB/c mice fed G50 culture produced more IL-12 and IFN-gamma and slightly less IL-4 and IL-6 than the control (i.e., without strain G50), indicating that strain G50 can enhance Th1-type immune response in vivo. The effect of the oral administration of strain G50 on antibody response in mice was also investigated. Mice were immunized with ovomucoid (OVM), a potent egg allergen, and the antibody level in the serum was then determined. The total IgE antibody level in the group treated with strain G50 was significantly lower than that of the control. The response of OVM-specific IgG1 and IgE antibodies tended to be low in the group that was administered strain G50, compared with the response of the control group. These results suggest that strain G50 has an ability to suppress the Th2 response. Thus, Lactococcus lactis subsp. lactis G50 is a potential probiotic strain for the suppression of hypersensitive reactions caused by the Th2 response.     

Carbonic acid as the host signal for the development of parasitic stages of nematodes

Petronijevic T., Rogers W. P. and Sommerville R. I. 1985. Carbonic acid as the host signal for the development of parasitic stages of nematodes. International Journal for Parasitology15: 661–667. This paper gives results on which may be based an identification of the component of the system CO₂ + H₂O ai H₂CO₃ ai H⁺ HCO₃^? which acts as the stimulus from the animal host for some nematodes. Using infective juveniles of Nematospiroides dubius and Haemonchus contortus, the effects on exsheathment of (1) low pCO₂ values, (2) the presence of carbonic anhydrase in the stimulating medium, and (3) the inhibition of carbonic anhydrase within the juveniles have been examined. The results lead to the suggestion that it is the “readily available” undissociated H₂CO₃, or H₂CO₃ + HCO₃^? which is the critical factor in the stimulus for development. The wide range of [H⁺]s over which “readily available” H₂CO₃ is present in physiological environments suggests that this host signal may be important for infection with many species.     

Undissociated bases as the stimulus for the development of early parasitic stages of nematodes

Petronijevic T. and Rogers W. P. 1987. Undissociated bases as the stimulus for the development of early parasitic stages of nematodes. International Journal for Parasitology 17 :911–915. The effects of NH₄Cl and NH₂CH₃ on infective stages of Haemonchus contortus, Nematospiroides dubius and Ascaris suum have been compared with the action of H₂CO₃. Detailed experiments were carried out with H. contortus. NH₄Cl at pH 8 under air was less toxic to infective stages than it was to free-living juveniles of Panagrellus redivivus. The induction of exsheathment or hatching by bases was slow (20–30 h) though the time of development of 4th stage H. contortus was not proportionally increased. Activity at pH 6 was less than that at pH 8. In contrast to the action of H₂CO₃ as the stimulus, NH₄Cl was not Ca²⁺-dependent. Prolonged exposure to anoxia at pH 8 was toxic, but in the presence of NH₄Cl or H₂CO₃ toxicity was decreased. The inhibition of exsheathment due to Dnp at pH 7 was greater when NH₄Cl was the stimulus.The process whereby host signals induce development of parasitic stages is discussed.     

Plant parasitic nematodes associated with the roots of wind toppled trees at the Royal Botanic Gardens, Kew

Root and soil samples from 21 trees blown down in Kew Gardens during the gales of October 1987 yielded 29 species of plant parasitic nematodes. Pratylenchus crenatus, P. thornei and P. penetrans were the only endoparasitic nematodes found. The common occurrence of P. crenatus and the root ectoparasitic nematodes, such as Merlinius microdorus, Paratrichodorus pachydermus and Rotylenchus robustus reflected the predominantly sandy nature of most of the soil samples. Species rarely recorded in Britain included Hemicriconemoides pseudobrachyurum, Paralongidorus maximus and Xiphinema pseudocoxi, all of which may be introductions.     

Effects of plumbagin on development of the parasitic nematodes Haemonchus contortus and Ascaris suum

1. Plumbagin (5-hydroxy,2-methyl-l,4-napthoquinone) inhibited the motility and survival of Haemonchus contonus first-stage larvae (L1) with an ed₅₀ of 1 μg/ml, but was less effective in preventing the development of H. contortus to infective third-stage larvae in a faecal slurry assay.2. Of the structural analogs tested, plumbagin was the most potent in preventing development of L1 followed in decreasing order of potency by 1,4-napthoquinone, 5-hydroxy-1,4-napthoquinone (juglone) and 1,2-napthoquinone.3. Plumbagin had a biphasic effect on development of the fourth-stage Ascaris suum larvae that caused an increase in growth at low concentrations but was lethal at higher doses.4. Plumbagin and 1,2-napthoquinone partially inhibited embryonation of A. suum eggs.     

Plant parasitic nematodes associated with ornamental plant Pseuderanthemum atropurpureum in Aligarh district of western Uttar Pradesh

A survey was conducted to determine the nematodes associated with the soil, substratum and roots of the ornamental plant, Pseuderanthemum atropurpureum, grown in the Aligarh district of western Uttar Pradesh, India. Ten genera of plant parasitic nematodes, viz. Meloidogyne spp., Helicotylenchus sp., Hemicriconemoides sp., Hoplolaimus sp., Xiphinema sp., Pratylenchus sp., Trichodorus sp., Tylenchorhynchus sp., Aphelenchoides sp. and Rotylenchus sp., were isolated from 345 soil samples collected from 15 different localities. Our study indicates that among the 10 genera of the plant parasitic nematodes, Meloidogyne spp. was widely spread in all the examined localities of Aligarh district, except at Khair. It was observed that the population density and diversity of nematodes in all the soil samples was not uniform. Meloidogyne spp. showed the highest absolute frequency and relative frequency followed by Helicotylenchus sp., Hemicriconemoides sp., Xiphinema sp., Hoplolaimus sp., Pratylenchus sp., Trichodorus sp., Tylenchorhynchus sp., Aphelenchoides sp. and Rotylenchus sp. Since no records are available in the literature related to the association of root-knot nematode in P. atropurpureum, it is worthy to note that this study may be considered as a new hope towards further study of the interaction between the root-knot nematode and ornamental plant P. atropurpureum if any.     

Experimental autoimmune myasthenia gravis may occur in the context of a polarized Th1- or Th2-type immune response in rats.

Experimental autoimmune myasthenia gravis (EAMG) is a T cell-dependent, Ab-mediated autoimmune disease induced in rats by a single immunization with acetylcholine receptor (AChR). Although polarized Th1 responses have been shown to be crucial for the development of mouse EAMG, the role of Th cell subsets in rat EAMG is not well established. In the present work we show that while the incidence and severity of EAMG are similar in Lewis (LEW) and Brown-Norway (BN) rats, strong differences are revealed in the immune response generated. Ag-specific lymph node cells from LEW rats produced higher amounts of IL-2 and IFN-gamma than BN lymph node cells, but expressed less IL-4 mRNA. IgG1 and IgG2b anti-AChR isotype predominated in BN and LEW rats, respectively, confirming the dichotomy of the immune response observed between the two strains. Furthermore, although IL-12 administration or IFN-gamma neutralization strongly influenced the Th1/Th2 balance in BN rats, it did not affect the disease outcome. These data demonstrate that a Th1-dominated immune response is not necessarily associated with disease severity in EAMG, not only in rats with disparate MHC haplotype but also in the same rat strain, and suggest that in a situation where complement-fixing Ab can be generated as a consequence of either Th1- or Th2-mediated T cell help, deviation of the immune response will not be an adequate strategy to prevent this Ab-mediated autoimmune disease.     

Effects of plumbagin on development of the parasitic nematodes Haemonchus contortus and Ascaris suum.

1. Plumbagin (5-hydroxy,2-methyl-1,4-napthoquinone) inhibited the motility and survival of Haemonchus contortus first-stage larvae (L1) with an ED50 of 1 microgram/ml, but was less effective in preventing the development of H. contortus to infective third-stage larvae in a faecal slurry assay. 2. Of the structural analogs tested, plumbagin was the most potent in preventing development of L1 followed in decreasing order of potency by 1,4-naphthoquinone, 5-hydroxy-1,4-napthoquinone (juglone) and 1,2-napthoquinone. 3. Plumbagin had a biphasic effect on development of the fourth-stage Ascaris suum larvae that caused an increase in growth at low concentrations but was lethal at higher doses. 4. Plumbagin and 1,2-napthoquinone partially inhibited embryonation of A. suum eggs.     

The physiology of infection with nematodes: the role of intracellular pH in the development of the early parasitic stage

1. H2CO3, the host's signal which induced (less than 25 min) the Ca2+-dependent development of the first parasitic stage of Haemonchus contortus, produced a diphasic change in the pHi (less than 30 min), measured with 5,5-dimethyl-2,4-oxazolidinedione, in the infective stage. The intensity of the diphasic change was related to the [H2CO3] and so to the efficiency of the stimulus for development. 2. MES and HEPES buffers induced a rapid rise in pHi of infective stages in step with pHo. Ortho-and pyrophosphate induced greater changes in pHi. Such buffers did not initiate development. 3. These and other results suggest that the stimulus for development, H2CO3, induced an energy-dependent Ca2+/H+ exchange mediated by mitochondria of the infective stage, which initiated development of the parasitic stage.     

Th1-type immune response to a Coccidioides immitis antigen delivered by an attenuated strain of the non-invasive enteropathogen Vibrio cholerae

The antigen-2 or proline rich antigen (Ag2/PRA) from Coccidioides immitis, known to protect mice against experimental Coccidioidomycosis, was expressed in the genetically attenuated cholera vaccine candidate Vibrio cholerae 638 and its thymine auxotrophic derivative 638T. Intranasal immunization of mice with strains producing Ag2/PRA induced serum vibriocidal antibody and Ag2/PRA-specific total IgG responses in outbred Swiss Webster and inbred BALB/c mice. Analysis of IgG subclasses showed a predominance of IgG2a subclass antibodies. Lymphocytes from immunized mice stimulated with pure Ag2/PRA showed a significant proliferative response with production of interferon-gamma. Positive selection for plasmid maintenance in vivo did not enhance immune response to Ag2/PRA. These results demonstrate that genetically attenuated strains of the non-invasive pathogen V. cholerae can be used to express and deliver foreign antigens to stimulate a Th1 type of immune response.