Expression of heat shock protein 70a mRNA in Bombyx mori diapause eggs

In an effort to understand whether heat shock protein 70 (Hsp70) participates in the environmental 5 °C signal reception/transduction toward breaking embryonic diapause of the silkworm Bombyx mori, we isolated a cDNA for Hsp70a and examined the expression of Hsp70a mRNA in B. mori diapause and nondiapause eggs by quantitative real-time PCR. Hsp70a mRNA gradually increased in diapause eggs continuously kept at 25 °C after oviposition to maintain diapause. When diapause eggs were exposed to the diapause-terminating condition of 5 °C beginning at 2 days post-oviposition, Hsp70a mRNA increased beginning at 5 days post-cold treatment. Even in nondiapause eggs, Hsp70a mRNA increased slightly with exposure to 5 °C. These results suggest that Hsp70a is involved in reception/transduction of the diapause-terminating (5 °C) signal via gene activation. The expression patterns of Hsp70a mRNA are discussed in relation to those of the cold-response gene Samui.     

Promoter variants at AP2 box region of Hsp70.1 affect thermal stress response and milk production traits in Frieswal cross bred cattle

Heat shock proteins (Hsp) are known to play major role in protection of cells from thermal stress. Nucleotide polymorphisms within the promoter of Hsp affect degree of expression and inducibility of Hsp mRNA. The present study aimed to investigate the effect of polymorphism within promoter region on the cellular expression of Hsp70.1 mRNA and association of identified polymorphisms with the physiological parameters during summer stress and milk production traits in dairy cattle. Two hundred Frieswal cows were genotyped using double PCR-RFLP to identify deletion of cytosine within the Hsp70.1 promoter AP2 box at base position 895. Homozygous wild type genotypes (CC) were found in lower frequency (39.29, n = 78) than heterozygous cytosine deletion mutant genotypes (C −) (60.71, n = 122). In the observed physiological parameters (rectal temperature, respiration rate and heat tolerance coefficient), cows that were homozygous wild types had better significant (P < 0.05) summer tolerance than the heterozygous deletion genotypes. Cytosine deletion mutation in the promoter region negatively affected (P < 0.01) the expression of Hsp70.1 mRNA in peripheral bovine mononuclear cells (PBMC) subjected to in vitro heat stress. Further association of observed polymorphism with the milk production traits was significant as the heterozygous cytosine deletion cows had lower total milk yield, peak yield, yield at 300 days, protein% (P < 0.01) and fat% (P < 0.05) than the native wild type promoter cows. The results from the present study suggest that the promoter region of bovine hsp70.1 gene is polymorphic and may be useful in selection of dairy cows for relatively better thermotolerance and higher milk production.     

Deficient heat shock protein 70 response to stress in leukocytes at onset of type 1 diabetes

Type 1 diabetes is caused by the immune-mediated destruction of pancreatic beta cells. Animal models of the disease demonstrate an increased susceptibility of beta cells to immunological attacks due to their defective stress-responsiveness. To investigate the stress-responsiveness in human type 1 diabetes we analyzed the heat-inducibility of the dominant stress protein heat shock protein (Hsp)70 in diabetic patients at different disease stages. At diabetes-manifestation heat-induced Hsp70 levels in peripheral blood mononuclear cells (PBMC) reached only about 25% of the levels expressed by heat-treated PBMC from non-diabetic subjects (p < 0.05). Heat-responsiveness improved with disease duration and was re-established at more than eight months after disease-manifestation. Hyperthermia-induced Hsp70 expression was decreased by the T-helper 1-associated cytokine interferon-γ and increased by the T-helper 2-associated transforming growth factor-β. We conclude that impaired cellular stress-responsiveness, aggravated by the inflammatory milieu at the onset of type 1 diabetes, contributes to disease manifestation.     

The expression of peptidoglycan recognition protein-S1 gene in the scallop Chlamys farreri was enhanced after a second challenge by Listonellaanguillarum

A more rapid and powerful response against repeated exposure of same pathogen in vertebrates is usually considered as the reflection of immunological memory, but it is not well understood in invertebrates. In the present study, the temporal expression profiles of Chlamys farreri peptidoglycan recognition protein-S1 (CfPGRP-S1) gene after two challenges of Listonella anguillarum were examined to evaluate priming response in scallops. The up-regulation of CfPGRP-S1 mRNA occurred 3 h earlier, and the expression level was significant higher (P < 0.05), after the second challenge than that after the first challenge. The preliminary results provided new insights into invertebrate immunological memory, and they also would be helpful to develop strategies for disease control.     

Caffeic acid, tyrosol and p-coumaric acid are potent inhibitors of 5-S-cysteinyl-dopamine induced neurotoxicity

Parkinson’s disease is characterized by a progressive and selective loss of dopaminergic neurons in the substantia nigra. Recent investigations have shown that conjugates such as the 5-S-cysteinyl-dopamine, possess strong neurotoxicity and may contribute to the underlying progression of the disease pathology. Although the neuroprotective actions of flavonoids are well reported, that of hydroxycinnamates and other phenolic acids is less established. We show that the hydroxycinnamates caffeic acid and p-coumaric acid, the hydroxyphenethyl alcohol, tyrosol, and a Champagne wine extract rich in these components protect neurons against injury induced by 5-S-cysteinyl-dopamine in vitro. The protection induced by these polyphenols was equal to or greater than that observed for the flavonoids, (+)-catechin, (−)-epicatechin and quercetin. For example, p-coumaric acid evoked significantly more protection at 1 μM (64.0 ± 3.1%) than both (−)-epicatechin (46.0 ± 4.1%, p < 0.05) and (+)-catechin (13.1 ± 3.0%, p < 0.001) at the same concentration. These data indicate that hydroxycinnamates, phenolic acids and phenolic alcohol are also capable of inducing neuroprotective effects to a similar extent to that seen with flavonoids.     

Cryopreservation of collared peccary (Pecari tajacu) semen using different freezing curves,straw sizes,and thawing rates

The objective of this study was to verify the effect of different freezing curves, straw sizes, and thawing rates on the cryopreservation of collared peccary semen. Twelve ejaculates were obtained from captive adult males by electroejaculation, and evaluated for sperm motility, kinetic rating, viability, morphology, and functional membrane integrity. The ejaculates were diluted in a coconut water extender (ACP-116c) with egg yolk and glycerol, packaged into 0.25 mL or 0.50 mL plastic straws and cryopreserved in liquid nitrogen following a slow (−10 °C/min) or a fast (−40 °C/min) freezing curve. After one week, samples were thawed at 37 °C/1 min or 70 °C/8 s and evaluated as reported for fresh semen, and also for kinematic parameters (computerized analysis). A significant decrease in sperm motility and kinetic rating was observed after glycerol addition at 5 °C and also after thawing for all the treatments (P < 0.05). Regarding post-thaw semen variables, no differences were verified between freezing curves when the same straw size and thawing rate were taken as reference (P > 0.05). In general, values for sperm characteristics found after thawing at 37 °C were better preserved than at 70 °C (P < 0.05), both in the use of 0.25 mL or 0.50 mL straws, which were similar for semen packaging (P > 0.05). The evaluation of the kinematic parameters of sperm motility confirmed these results at values varying from 20% to 30% motile sperm for the samples thawed at 37 °C, and values fewer than 12% motile sperm for samples thawed at 70 °C (P < 0.05). In conclusion, we recommend the use of a fast freezing curve that reduces the time spent on the cryopreservation of collared peccary semen, which could be packaged both in 0.25 mL or 0.50 mL straws, but the thawing should be conducted at 37 °C/1 min.     

Dobutamine mediates cytoprotection by induction of heat shock protein 70 in vitro

Aims

Dobutamine is cytoprotective when applied before a subsequent stress. However, the underlying molecular mechanism is unknown. Dobutamine also inhibits nuclear factor (NF)-κB in human T lymphocytes. Other inhibitors of NF-κB induce a so-called heat shock response. We hypothesized that dobutamine mediates protection from apoptotic cell death by the induction of a heat shock response.

Main methods

Jurkat T lymphoma cells were preincubated with dobutamine (0.1, 0.5 mM) before the induction of apoptosis (staurosporine, 2 μM). DNA-binding of heat shock factor (HSF)-1 was analyzed by electrophoretic mobility shift assay, mRNA-expression of heat shock protein (hsp)70 and hsp90 by Northern Blot, activity of caspase-3 by fluorogenic caspase activity assay and cleavage of pro-caspase-3 by Western Blot. Apoptosis was assessed by flow cytometry after annexin V-fluorescein isothiocyanate staining. Hsp70 and hsp90 were inhibited using N-formyl-3,4-methylenedioxy-benzylidene-gamma-butyrolaetam and 17-allylamino-17-demethoxygeldana-mycin, respectively. All data are given as median and 25/75% percentile.

Key findings

Pre-incubation with dobutamine inhibited staurosporine-induced annexin V-fluorescence (28 [20–32] % vs. 12 [9–15] % for dobutamine 0.1 mM and 7 [5–12] % for dobutamine 0.5 mM, p < 0.001), cleavage of pro-caspase-3 as well as caspase-3-like activity (0.46 [0.40–0.48] vs. 0.32 [0.27–0.39] for Dobutamine 0.1 mM and 0.20 [0.19–0.23] for Dobutamine 0.5 mM, p < 0.01). Dobutamine induced DNA-binding of HSF-1 and mRNA-expression of hsp70 and hsp90. While inhibition of Hsp90 had no effect, inhibition of Hsp70 increased the number of annexin V-positive cells (33 [32–36] % vs. 18 [16–24] %) and caspase-3-like activity (0.21 [0.19–0.23] vs. 0.16 [0.13–0.17], p < 0.05).

Significance

Dobutamine protects from apoptotic cell death via the induction of Hsp70.     

Growth and IGF-I response of juvenile Nile tilapia (Oreochromis niloticus) to changes in water temperature and dietary protein level

Water temperature and dietary protein level play an important role in influencing the growth and insulin-like growth factor I (IGF-I) in Nile tilapia juveniles. The combined effect of temperature (20–34 °C) and dietary protein level (25–50%) on the specific growth rate (SGR), feed efficiency (FE), serum IGF-I level and hepatic IGF-I mRNA level was examined under laboratory conditions by employing central composite design and response surface method. Results showed that the linear effects of temperature and dietary protein level on the SGR, FE, serum IGF-I and hepatic IGF-I mRNA level were significant (P<0.05); the quadratic effects of temperature and dietary protein level on the FE and serum IGF-I were significant (P<0.05). The interaction of temperature and dietary protein level on the FE, serum IGF-I and hepatic IGF-I mRNA level all proved significant (P<0.05). The optimal temperature/dietary protein level combination was determined, i.e., 29.9 °C/40.3%, at which the greatest SGR (2.748%/d) and FE (0.775) were simultaneously arrived. Both SGR and FE were linearly correlated with serum IGF-I or hepatic IGF-I mRNA level. These results suggested that optimum combination of temperature and dietary protein level would enhance tilapia growth efficiency and IGF-I would regulate growth and FE.     

Distinct chemical contaminants induce the synthesis of Hsp70 proteins in green microalgae Desmodesmus subspicatus: Heat pretreatment increases cadmium resistance

Using western-blotting techniques, we examined the effect of differently acting contaminants, such as anthracene (PAH), cadmium (heavy metal) and chloridazone (herbicide), as well as heat shock on the production of two Hsp70 proteins (cytoplasmic and stromal) in planktonic algae Desmodesmus subspicatus. All contaminants applied stimulated production of both Hsp70s in a concentration-dependent manner, but heat shock treatment turned out to be the most effective. Heat shock pretreatment (for 1 h at 40 °C) induced tolerance to cadmium in algal cells (measured by changes in growth rate), but not to anthracene or chloridazone. Two Hsp70s from D. subspicatus cells representing cytoplasmic and stromal proteins were purified by ATP-affinity chromatography.     

Thermotolerance and HSP70 expression in the Mediterranean fruit fly Ceratitis capitata

The relationship between Hsp70 expression and thermotolerance has been well documented in Drosophila melanogaster. However, there is limited information on this relationship in other insect species. In this report we describe the Hsp70-thermotolerance relationship in one of the major fruit fly pests, Ceratitis capitata (medfly). Hsp70 expression and thermotolerance were assayed at a range of temperatures in several stages of medfly development. The most thermotolerant stage was found to be the late larval stage (100% survival at 41 °C) followed by adult flies and late embryos (100% survival at 39 °C). These three stages showed a positive relationship between Hsp70 expression and thermotolerance. Mid-larval and mid-embryonic stages were found less thermotolerant and the Hsp70-thermotolerance relationship was not evident. Early embryos did not express Hsp70 at any temperature and exhibited the lowest thermotolerance. The relationship between Hsp70 and inducible thermotolerance was also studied in late larvae. A pretreatment at 37-39 °C increased thermotolerance at higher temperatures by approximately 1 °C. In parallel, the pretreatment increased Hsp70 expression suggesting a close link between Hsp70 expression and inducible thermotolerance. The increased Hsp70 levels after pretreatment were found to be due to the increased levels of the hsp70 RNA.     

Effect of water temperature,salinity, and their interaction on growth,plasma osmolality,and gill Na,K-ATPase activity in juvenile GIFT tilapia Oreochromis niloticus (L.)

We used a central composite rotatable experimental design and response surface methodology to evaluate the effects of temperature (18–37 °C), salinity (0–20‰), and their interaction on specific growth rate (SGR), feed efficiency (FE), plasma osmolality, and gill Na⁺, K⁺-ATPase activity in GIFT tilapia juveniles. The linear and quadratic effects of temperature and salinity on SGR, plasma osmolality, and gill Na⁺, K⁺-ATPase activity were statistically significant (P<0.05). The interactive effects of temperature and salinity on plasma osmolality were significant (P<0.05). In contrast, the interaction term was not significant for SGR, FE, and gill Na⁺, K⁺-ATPase activity ⁽P>0.05). The regression equations for SGR, FE, plasma osmolality, and gill Na⁺, K⁺-ATPase activity against the two factors of interest had coefficients of determination of 0.944, 0.984, 0.966, and 0.960, respectively (P<0.01). The optimal temperature/salinity combination was 28.9 °C/7.8‰ at which SGR (2.26% d¹) and FE (0.82) were highest. These values correspond to the optimal temperature/salinity combination (29.1 °C/7.5‰) and the lowest plasma osmolality (348.38 mOsmol kg⁻¹) and gill Na⁺, K⁺-ATPase activity (1.31 µmol Pi. h⁻¹ g⁻¹ protein), and resulted in an energy-saving effect on osmoregulation, which promoted growth.     

Long-term changes in macrophyte vegetation after reduction of fish stock in a shallow lake

Starting in the middle of the 1970s, submerged macrophytes began to disappear from shallow Lake Warniak due to feeding pressure by grass carp (Ctenopharyngodon idella). In the middle of the 1980s, the lake was stocked with seston-feeding silver carp (Hypophthalmichthys molitrix) and bighead carp (Aristichthys nobilis). By 1993, the biomass of silverhead carp and bighead carp had declined. This allowed charophytes to recolonize the bottom of the lake. The main charophyte species at this time were Chara globularis and Chara rudis. Since then, five other stonewort species have been found: Chara contraria, C. filiformis, C. tomentosa, C. aspera and Nitellopsis obtusa. Seventeen species of aquatic angiosperms have also been found. There were distinct changes in the relative abundance and spatial distribution of particular species. C. rudis developed most intensely in the shallow parts of the lake near the southern and western shores. C. globularis gradually took over the deeper central part of the lake. In 2001, C. rudis began to retreat again. The relative abundance and spatial distribution of charophytes was correlated to water clarity (r = 0.87, p < 0.05), total phosphorus level (r = −0.78; p < 0.05), and chlorophyll a content (r = −0.79; p < 0.05).     

Leaf press juice from Bryophyllum pinnatum (Lamarck) Oken induces myometrial relaxation

Aims

The use of preparations from Bryophyllum pinnatum (Lamarck) Oken (Kalanchoe pinnata (Lamarck) Persoon) in tocolysis is supported by clinical evidence. We studied here the effect of B. pinnatum leaf press juice and its chemical fractions on the response of human myometrial strips. No data are available if the influence on myometrial strips of the juice differs from that of its components in the chemical fractions, in order to increase the pharmacological effect.

Methodology

In vitro study to test the effect of repeated addition of B. pinnatum leaf press juice (BPJ) and its chemical components in several dilutions (undiluted, 1-10%) on myometrium strips hang up in a myograph chamber. Chemical analysis is including HPLC, MPLC with Sephadex LH-20 and TLC.

Results

All test solutions are inhibiting contractility by reducing the amplitude and the area under the curve (AUC) of the contractions. Undiluted BPJ and its undiluted chemical fraction 4 are reducing most effective these two parameters: the amplitude was at 78% of the baseline (95% CI (77-89); p < 0.05) at the second addition of the BPJ and at 70% (95% CI (50-90); p < 0.05) of the first addition of fraction 4; the AUC was at 82% (95% CI (69-95); p < 0.05) of the baseline at the first addition of the press juice and at 51% (95% CI (27-74); p < 0.05) at the first addition of fraction 4. The BPJ decreased amplitude and AUC significantly faster and increased frequency significantly faster than the control. Fractions could be tentatively assigned to bufadienolids, flavonoids and cinnamic acids. Fraction 4, accounted for flavonoids, increased the frequency of the contractions most effectively: 557% of the baseline (95% CI (316-797); p < 0.05) at the first addition.

Conclusion

Leaf juice of B. pinnatum and its flavonoid fraction are most effective in relaxing myometrial strips by inducing frequency.     

Anti-fatigue activity of polysaccharides extract from Radix Rehmanniae Preparata

The anti-fatigue effects of the Radix Rehmanniae Preparata polysaccharides (RRPP) were studied in mice. The RRPP were orally administered at doses of 50, 100 and 200 mg/kg for 4 weeks and the anti-fatigue activity was evaluated using a weight-loaded swimming test, along with the determination of serum urea nitrogen (SUN), hepatic glycogen and blood lactic acid (BLA) contents. The results showed that there was no significant difference in the body weight of mice in the three RRPP groups compared with the negative control group during initial, intermediate and terminal stages in the experiment (p > 0.05). The ratio of exhausting swimming time was obviously increased 31.48% (p < 0.05) and 61.51% (p < 0.01) in the middle-dose group and the high-dose RRPP group, respectively. The BLA and SUN levels were decreased in middle-dose and high-dose RRPP groups (p < 0.01). Hepatic glycogen level was increased in three RRPP treated groups (p < 0.01). Therefore, RRPP may be responsible for the pharmacological effect of anti-fatigue of Radix Rehmanniae Preparata. The mechanism was related to the increase of the storage of hepatic glycogen and the decrease of the accumulation of SUN and BLA.     

Partial protective responses induced by a recombinant cysteine proteinase from Leishmania (Leishmania) amazonensis in a murine model of cutaneous leishmaniasis

A 500 bp fragment encoding an isoform of cysteine proteinase from Leishmania (Leishmania) amazonensis was subcloned and expressed in the pHis vector, resulting in a recombinant protein of 24 kDa, rLacys24. In Western blots of L. (L.) amazonensis extracts, antibodies directed to rLacys24 recognized a cysteine proteinase isoform of 30 kDa. Analysis by fluorescence-activated cell sorter showed a significantly higher expression of CD8⁺ lymphocytes in animals immunized with rLacys24 plus CFA, whereas a low expression of CD4⁺ lymphocytes was observed in these animals. The cytotoxicity of lymphocytes isolated from mice immunized with rLacys24 plus CFA on L. (L.) amazonensis-infected macrophages was significantly higher than that observed in the presence of lymphocytes from control animals. Immunization of BALB/c mice with rLacys24 plus CFA resulted in a low but significant decrease of foot lesions after challenge with L. (L.) amazonensis compared to those exhibited by control mice.     

Protective effects of alkaloid extract from Leonurus heterophyllus on cerebral ischemia reperfusion injury by middle cerebral ischemic injury (MCAO) in rats

The neuronal damage following cerebral ischemia is a serious risk to stroke patients. The aim of this study was to investigate the neuroprotective effects of alkaloid extract from Leonurus heterophyllus (LHAE) on cerebral ischemic injury. After 24 h of reperfusion following ischemia for 2 h induced by middle cerebral artery occlusion (MCAO), some rats were intraperitoneally administered different doses of LHAE (3.6, 7.2, 14.4 mg/kg, respectively). Neurological examination was measured in all animals. Infarct volume, myeloperoxidase (MPO) activity, levels of nitrate/nitrite metabolite (NO) and apoptosis ratio of nerve fiber in brain were determined. The results showed that LHAE at 7.2 mg/kg or 14.4 mg/kg exerted significantly decreasing neurological deficit scores and reducing the infarct volume on rats with focal cerebral ischemic injury (p < 0.05). At those dose, the MPO content were significantly decreased in ischemic brain as compared with model group (p < 0.05). LHAE at 14.4 mg/kg significantly decreased the NO level compared with the model group (p < 0.05). In addition, LHAE significantly decreased the apoptosis ratio of nerve fiber compared with the model group (p < 0.05). This study suggests that LHAE may be used for treatment of ischemic stroke as a neuroprotective agent. Further studies are warranted to assess the efficacy and safety of LHAE in patients.     

Simultaneous detection of Giardia lamblia and Cryptosporidium parvum (oo)cysts in soil using immunomagnetic separation and direct fluorescent antibody staining

An improved approach for simultaneous detection of Cryptosporidium parvum and Giardia lamblia (oo)cysts in soil is described. Recoveries > 70% were obtained for concentrations > 55 and 21 (oo)cysts g ⁻¹ for C. parvum and G. lamblia, respectively. The limits of detection were determined to be < 5 (oo)cysts g ⁻¹ soil.     

Population genetics studies of half-smooth tongue sole Cynoglossus semilaevis using ISSR markers

Inter-simple sequence repeat (ISSR) analysis was performed in order to evaluate the genetic diversity of wild and hatchery samples of half-smooth tongue sole Cynoglossus semilaevis. A group of 200 genotypes belonging to four wild samples, Laizhou (LZ), Weihai (WH), Qingdao (QD), Rizhao (RZ) and one hatchery sample, Mingbo (MB) were screened using 15 different ISSR primers. A total of 137 loci were produced in the five studied samples. 41.80%, 45.26%, 44.27%, 42.86% and 41.59% of these loci were polymorphic over all the genotypes tested in LZ, WH, QD, RZ and MB samples, respectively. The number of polymorphic loci detected by single primer combination ranged from 2 to 7. The average heterozygosity of LZ, WH, QD, RZ and MB samples were 0.0710, 0.0814, 0.0793, 0.0727 and 0.0696, respectively. The WH sample showed a higher genetic diversity including total number of ISSR bands (P < 0.05), total number of polymorphic bands (P < 0.05), average heterozygosity (P < 0.05) and total number of genotypes (P < 0.05) than all the other samples. Among the five studied samples, the hatchery sample (MB) showed the lowest genetic viability.     

Effects of Echinaforce treatment on ex vivo-stimulated blood cells

The herb Echinacea purpurea, also called purple coneflower, is regarded as an immune modulator. This study examined changes in cytokine production in blood samples from 30 volunteers before and during 8-day oral administration with an ethanolic extract of fresh Echinacea purpurea (Echinaforce^®). Daily blood samples were ex vivo stimulated by LPS/SEB or Zymosan and analysed for a series of cytokines and haematological and metabolic parameters. Treatment reduced the proinflammatory mediators TNF-α and IL-1β by up to 24% (p < 0.05) and increased anti-inflammatory IL-10 levels by 13% (p < 0.05) in comparison to baseline. This demonstrated a substantial overall anti-inflammatory effect of Echinaforce^® for the whole group (n = 28). Chemokines MCP-1 and IL-8 were upregulated by 15% in samples from subjects treated with Echinaforce^® (p < 0.05). An analysis of a subgroup of volunteers who showed low pre-treatment levels of the cytokines MCP-1, IL-8, IL-10 or IFN-γ (n = 8) showed significant stimulation of these factors upon Echinaforce^® treatment (30-49% increases; p < 0.05), whereas the levels in subjects with higher pre-treatment levels remained unaffected. We chose the term “adapted immune-modulation” to describe this observation. Volunteers who reported high stress levels (n = 7) and more than 2 colds per year experienced a significant transient increase in IFN-γ upon Echinaforce^® treatment (>50%). Subjects with low cortisol levels (n = 11) showed significant down-regulation of the acute-phase proteins IL1-β, IL-6, IL-12 and TNF-α by Echinaforce^® (range, 13-25%), while subjects with higher cortisol levels showed no such down-regulation. This is the first ex vivo study to demonstrate adapted immune-modulation by an Echinacea preparation. While Echinaforce^® did not affect leukocyte counts, we speculate that the underlying therapeutic mechanism is based on differential multi-level modulation of the responses of the different types of leukocytes. Echinaforce^® thus regulates the production of chemokines and cytokines according to current immune status, such as responsiveness to exogenous stimuli, susceptibility to viral infection and exposure to stress.