IgG absorption by Santa Ines lambs fed Holstein bovine colostrum or Santa Ines ovine colostrum

The objective of this study was to evaluate the immunoglobulin G (IgG) absorption by Santa Ines lambs under two colostrum management systems usually used by producers. Twenty-seven Santa Ines newborn lambs received two meals of 250 ml of bovine colostrum from Holstein cows (BC group) or ovine colostrum from Santa Ines ewes (OC group) at 0 and 6 h of life. Pools of BC and OC were analyzed by radial immunodiffusion to quantify IgG. Results are expressed as least-square means and standard errors of mean (means ± s.e.m.). The concentration of IgG in bovine and ovine pools averaged 115.7 ± 20.5 and 48.1 ± 5.0 mg/ml, respectively, levels of concentration found in similar regular colostrum managements. The efficiency of IgG absorption was evaluated under two aspects, maximum apparent efficiency of absorption and total apparent efficiency of absorption (AEAmax and AEAtotal, respectively). The AEAmax was calculated taking into account the mass of IgG ingested just in the first meal of colostrum at birth and the serum IgG concentration at 6 h while the AEAtotal took into account the serum IgG concentration at 24 h of life that reflects the first colostrum offered at birth and the second meal at 6 h. The IgG and apparent efficiency of absorption results were transformed into the square root and log base 10, respectively, and were presented as geometric least-square means. In BC, lower (P < 0.05) AEAmax and AEAtotal were verified (14.2% and 15.6%, respectively), in relation to OC (23.6% and 24.4%, respectively). Serum IgG concentrations at 24 h were significantly higher (P < 0.05) in BC (31.4 mg/ml, respectively) compared with OC (22.2 mg/ml, respectively). The results in this study confirm that there is a limitation to the process of IgG absorption by the enterocytes of newborn lambs, which determined a nonlinear behavior of passive immunity acquisition. Similar values of AEAmax and AEAtotal for the two sources of colostrum reveal that the process of IgG absorption from the first and second meals during the first 6 h of life did not change and indicates that the ingestion of a second feeding of quality colostrum can enhance the acquisition of immune protection of newborn lambs.     

Suppression of CD4 T-Cells in the spleen of mice infected with Toxoplasma gondii KI-1 tachyzoites

Toxoplasma gondii KI-1, a recent new isolate from Korea, shows similar pathogenicity and infectivity to mice compared to the virulent RH strain. To understand characteristics of host immunity, including immune enhancement or suppression, we investigated proliferative responses and phenotypes of spleen cells. In addition, kinetics of IFN-γ, a Th1 cytokine, was examined in BALB/c mice up to day 6 post-infection (PI). Intraperitoneal injection of mice with 10(3) KI-1 tachyzoites induced significant decreases (P < 0.05) in proliferative responses of spleen cells. This occurred at days 2-6 PI even when concanavalin A (con A) was added and when stimulated with KI-1 antigen, suggesting suppression of the immunity. CD4(+) T-cells decreased markedly at day 2 PI (P < 0.05), whereas CD8(+) T-cells, NK cells, and macrophages did not show significant changes, except a slight, but significant, increase of CD8(+) T-cells at day 6 PI. The capacity of splenocytes to produce IFN-γ by con A stimulation dropped significantly at days 2-6 PI. These results demonstrate that intraperitoneal injection of KI-1 tachyzoites can induce immunosuppression during the early stage of infection, as revealed by the decrease of CD4(+) T-cells and IFN-γ.     

Epidemics with partial immunity to reinfection

We obtain analytical results about epidemics generated by the partial immunity model of Gomes et al. [3], in which infection confers partial immunity to reinfection. When the demographic process is excluded, the behavior switches from epidemic to endemic as the basic reproduction number R₀ crosses the reinfection threshold . We derive formulas for two quantities characterizing the size of the epidemic below the reinfection threshold: the attack rate A, which is the fraction of the population infected at least once, and the final size Z, which is the average number of infections per individual. We also derive a system of differential equations which can be used to obtain more detailed information, such as the fraction of the population infected n times throughout the epidemic, for every n.     

Ultrastructural and functional characterization of circulating hemocytes from Plutella xylostella larva: Cell types and their role in phagocytosis

The hemocytes of different types encountered in the diamondback moth Plutella xylostella larvae of each instar and the development of the differential hemocytes counts were herein presented. Hemocytes classes/populations characterized based on their affinity with fluorescent dye (acridine orange) and ultrastructural differences comprised the prohemcoytes (<10–16%), plasmatocytes (22–65%), granulocytes (25–72%), oenocytoids (<1–9%), and spherulocytes (<1%). Prohemcoytes were the smallest cells with a comparatively tremendous nucleus. Plasmatocytes and granulocytes occupied the main proportion of total cell numbers. Oenocytoids were in a most stable presence, i.e. rotund in a diameter of 10 μm and with a nucleus deviated from the central location; however, sometimes with two nuclei which were adjoining with each other. Spherulocytes were rare and only could be observed occasionally. Ultrastructural investigation revealed that hemocytes in the diamondback moth larvae were of the typical model as in the Lepidoptera insect larvae. It is interesting to find that the cell which could phagocytize bacteria in vitro was granulocyte, not the other types of hemocytes, although plasmatocyte was usually declared to participate in this reaction in various previous studies.     

A thioredoxin response to the WSSV challenge on the Chinese white shrimp, Fenneropenaeus chinensis

Thioredoxin (TRX) is involved in cell redox homeostasis. In addition, it is responsible for maintaining proteins in their reduced state. In our study, a Fenneropenaeus chinensis thioredoxin (FcTRX) gene was identified from the Chinese white shrimp. The full length of FcTRX was 777 bp, including a 60 bp 5′ untranslated region (UTR), a 318 bp open reading frame (ORF) encoding a 105 amino acids protein, and a 399 bp 3′ UTR. FcTRX contained a TRX domain with a conserved motif of Cys-Gly-Pro-Cys (CGPC). No signal peptide was predicted by SMART analysis. The molecular mass and pI of FcTRX were 12 kDa and 4.62, respectively. FcTRX is a widely distributed gene, and its mRNA is detected in hemocytes, hearts, hepatopancreas, gills, stomach, and intestine from an unchallenged shrimp. The expression level of FcTRX was the highest in hepatopancreas, where it was down-regulated to the lowest level at 12 h white spot syndrome virus (WSSV) challenge. In the gills, it went up to the highest level at 6 h. Western blot showed that FcTRX protein in hepatopancreas challenged with WSSV was down-regulated from 2 h to 12 h and then restored to the level similar to that of unchallenged shrimp at 24 h. In the gills challenged with WSSV, the FcTRX protein was up-regulated from 6 h to 24 h. Our research indicated its possible role in the anti-WSSV innate immunity of shrimps.     

Metabolic stress suppresses humoral immune function in long-day,but not short-day,Siberian hamsters (<Emphasis Type="Italic">Phodopus sungorus</Emphasis>)

Individuals of many species experience marked seasonal variation in environmental conditions and must adapt to potentially large fluctuations in energy availability and expenditure. Seasonal changes in immunity have likely evolved as an adaptive mechanism to cope with seasonal stressors. In addition, these changes may be constrained by seasonal fluctuations in energy availability. The goal of this study was to assess the role of energetic trade-offs associated with seasonal variation in immunity. In addition to body fat stores, metabolic fuels (e.g., glucose) may affect immune function in seasonally breeding rodents. In this study we experimentally reduced energy availability via injections of the metabolic inhibitor 2-deoxy-d-glucose (2-DG) in long- and short-day housed Siberian hamsters (Phodopus sungorus) and then examined antigen-specific antibody production. Metabolic stress decreased antibody response compared with control animals in long days. In contrast, no difference was observed between treatment groups in short days. These data suggest that reductions in energy availability suppress immunity and short days buffer organisms against glucoprivation-induced immunosuppression.     

Identification of squalamine in the plasma membrane of white blood cells in the sea lamprey, Petromyzon marinus

It is well established that innate mechanisms play an important role in the immunity of fish. Antimicrobial peptides have been isolated and characterized from several species of teleosts. Here, we report the isolation of an antimicrobial compound from the blood of bacterially challenged sea lamprey, Petromyzon marinus. An acetic acid extract from the blood cells of challenged fish was subjected to solid-phase extraction, cation-exchange chromatography, gel-filtration chromatography, and reverse-phase high-performance liquid chromatography, with the purified fractions assayed for antimicrobial activity. Surprisingly, antimicrobial activity in these fractions originated from squalamine, an aminosterol previously identified in the dogfish shark, Squalus acanthias. Further chromatographic and mass spectrometric analyses confirmed the identity of squalamine, an antimicrobial and antiangiogenic agent, in the active fraction from the sea lamprey blood cells. Immunocytochemical analysis localized squalamine to the plasma membrane of white blood cells. Therefore, we postulate that squalamine has an important role in the innate immunity that defends the lamprey against microbial invasion. The full biochemical and immunological roles of squalamine in the white blood cell membrane remain to be investigated.     

Patterns of nucleotide sequence variation in <Emphasis Type="Italic">ICAM1</Emphasis> and <Emphasis Type="Italic">TNF</Emphasis> genes in twelve ethnic groups of India: roles of demographic history and natural selection

We have studied DNA sequence variation in and around the genes ICAM1 and TNF, which play functional and correlated roles in inflammatory processes and immune cell responses, in 12 diverse ethnic groups of India, with a view to investigating the relative roles of demographic history and natural selection in shaping the observed patterns of variation. The total numbers of single nucleotide polymorphisms (SNPs) detected at the ICAM1 and TNF loci were 29 and 12, respectively. Haplotype and allele frequencies differed significantly across populations. The site frequency spectra at these loci were significantly different from those expected under neutrality, and showed an excess of intermediate-frequency variants consistent with balancing selection. However, as expected under balancing selection, there was no significant reduction of F _ST values compared to neutral autosomal loci. Mismatch distributions were consistent with population expansion for both loci. On the other hand, the phylogenetic network among haplotypes for the TNF locus was similar to expectations under population expansion, while that for the ICAM1 was as expected under balancing selection. Nucleotide diversity at the ICAM1 locus was an order of magnitude lower in the promoter region, compared to the introns or exons, but no such difference was noted for the TNF gene. Thus, we conclude that the pattern of nucleotide variation in these genes has been modulated by both demographic history and selection. This is not surprising in view of the known allelic associations of several polymorphisms in these genes with various diseases, both infectious and noninfectious.