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Since the fruits and leaves of the Olive (Olea europea) tree, which grows naturally in Mediterranean countries, are thought to be beneficial for many diseases, it is widely used in folk medicine in these countries. Olive leaf extract has been used in the treatment of many diseases such as malaria, high fever, heart diseases and cancer. The greater wax moth Galleria mellonella (Lepidoptera: Pyralidae) is frequently used in invertebrate immunity studies due to its similarity to the mammalian natural immune system. Melanization occurs when quinone precursors are converted to melanin and inactive profenoloxidase to phenoloxidase enzyme. In this study, the phenoloxidase activity of G. mellonella hemolymph larvae injected with olive leaf extract in different doses was determined by ELISA microplate reader at 492 nm absorbance. The findings obtained from this study showed that olive leaf extract increased phenoloxidase activity at a dose of 0.001 mg mL-1. Lower doses of 0.001 mg mL-1 did not cause changes in phenoloxidase activity compared to the untreated and Dimethyl Sulfoxide (DMSO) groups. The highest olive leaf extract dose of our study is 0.01 mg mL-1 and the larvae did not survive for 24 hours over those doses. The results of our study show that olive leaf supports humoral immune responses when used in low doses.

Endoparasitoid species devoid of symbiotic viruses inject secretions derived from their reproductive glands into their hosts during parasitism in order to avoid various immune responses of their hosts. Pimpla turionellae L. (Hymenoptera: Ichneumonidae) is an endoparasitoid that lacks polydnaviruses, and its venom has previously been shown to paralyze the host Galleria mellonella (Lepidoptera: Pyralidae) and suppress its immune reactions to ensure the egg survival. The present study demonstrates that another female-injected factor calyx fluid extracted from the P. turionellae ovary is also responsible for the suppression of G. mellonella immunity. The total hemocyte counts of G. mellonella decrease after treatment with calyx fluid in a concentration-dependent manner. Significant reductions in cell viability are also observed at all calyx fluid doses both in vivo and in vitro. The analyses of the beads injected into the insects as encapsulation targets revealed that the number of encapsulated beads reduced significantly compared to controls post-calyx fluid injection. The injection of the highest calyx fluid dose (1 female equivalent calyx) is sufficient to completely inhibit the strong encapsulation and melanization reactions of the last instar larvae 24 h post-injection. These results demonstrate that P. turionellae calyx fluid is required to regulate host immunity for successful parasitization.

Immune responses play a key role in the survival of all living things. Intake of inorganic materials is of critical importance in living organisms because of their participation in metabolism and some component of cells. Iron (Fe), magnesium (Mg) and selenium (Se) were selected for this study because of their participation in critical constituents of cells, such as nucleic acids and enzymes in living organisms, and their indirect and direct effects on immunity. Although the separate effects of these inorganic materials are known, there is no study on their combined effects. Galleria mellonella, which is used as a model organism, is frequently used in evaluating of effects of human pathogens due to its various properties. Total hemocyte counts and encapsulation-melanization responses are the most commonly observed parameters when examining the immune responses of this model organism. In our study, the effects of the selected inorganic materials added in the ratio of 0.1%, 0.25%, 0.5% and 1% in the nutrient content of Galleria mellonella on the immune responses of this organism were investigated. As a result of the study, it was found that only 0.25% of the doses increased the hemocyte count and that the other doses significantly decreased compared to the control group. However, it was determined that 0.5% and 1% feeding caused a significant decrease in both hemocyte count and encapsulation-melanization responses. According to our findings, the nutrients which have over a certain dose by inorganic substances have negative effects on immunity.

Helichrysum arenarium (L.) (Asterales:Asteraceae) Moench is a therapeutic plant which contains etheric oil, flavones and flavon glycosides, sterins, bitter substances and tannins having various coumarins. This plant is thought to have important characteristics such as diuretic effect, dropping stones and sand from the kidney, regulating digestive disorders, strengthening the immune system, and having antibiotic and antioxidant effects. Additionally, this plant is traditionally used in liver and biliary tract diseases and also shows anti-inflammatory and detoxifying properties. Model organism Galleria mellonella L. (Lepidoptera:Pyralidae) is an invertebrate species that is frequently used to study the effects of human pathogens and various pesticides, hormones, etc. on immune system. In our study, we examined the effect of various doses of H. arenarium on the hemocyte count and behavior of G. mellonella larvae. According to the findings obtained at the end of our study, H. arenarium caused an increase in hemocyte count with the injection of 0.25% and 0.5% doses compared to the untreated and DMSO groups. At the same time, the 0.25% and 0.5% doses showed a strong encapsulation-melanization response and an increase in phenoloxidase enzyme activity over 24 h compared to the other injected groups. Based on these results, H. arenarium extract has an anti-mitotic activity at high doses (above 0.5%). This effect may be due to the fact that the plant extract supports mitosis at a certain dose, while being toxic when exceeding it.

Pyrethrum is a natural neurotoxic insecticide which is obtained from the flowers of Chrysanthemum cinerariaefolium plant. Pyrethrum extract causes DNA damage, genotoxic effect, induction of autophagy and apoptosis, mitochondrial dysfunction, oxidative stress, inhibition of biochemical processes. The greater wax moth Galleria mellonella L. (Lepidoptera: Pyralidae) is gaining increasing attention in immunity studies as an invertebrate model organism. Melanization, which is the most important response of invertebrate humoral immunity, occurs when inactive prophenoloxidase turns into phenoloxidase enzyme. Changes in phenoloxidase enzyme activity are an important marker for humoral immunity. In our study, the phenoloxidase enzyme activity of hemolymph collected from G. mellonella larvae treated with different doses of pyrethrum extract was determined by reading against a certain absorbance in an ELISA microplate reader. The findings obtained from this study showed that 0.6 mg/ml pyrethrum extract increased phenoloxidase enzyme activity. Doses above and below this dose did not cause a significant change in phenoloxidase activity compared to control groups. In the evaluation made in terms of the change of enzyme activity over time, while the enzyme activity increased rapidly in the first 15 minutes, the enzyme activity rate decreased after the 20th minute. The effect of pyrethrum extract on phenoloxidase enzyme activity in G. mellonella larval hemolymph at a certain dose is consistent with the literature. The reason for this effect of the extract is closely related to its genotoxic and cytotoxic effects.

The dietary effects of the well-known auxin member plant growth regulator, indole-3-acetic acid (IAA), on hemocyte counts and behavior of the model insect Galleria mellonella L. (Lepidoptera: Pyralidae) and its parasitoid Pimpla turionellae L. (Hymenoptera: Ichneumonidae) were examined. In vivo and in vitro experiments involved five treatments applied to larvae with doses of 50, 500, 1000, 5000, and 10000 ppm IAA and the controls. Total hemocyte counts increased at all applied IAA doses in G. mellonella whereas no effect was observed in P. turionellae. According to acridine orange-ethidium bromide double staining, none of the IAA doses affected the ratio of apoptotic and mitotic cells in vivo however a decrease in the number of late apoptotic cells at 1000 and 5000 ppm was observed at in vitro experiments in G. mellonella. An increase in the percentage of early apoptotic hemocytes at 1000 ppm and late apoptotic hemocytes at 500 ppm were determined in P. turionellae larvae. IAA also increased the ratio of mitotic hemocytes in the circulation of P. turionellae larvae at 50, 1000, and 10000 ppm. Changes in the encapsulation rate of Sephadex A-25 beads were not significant however the increase at 5000 ppm at 4th hour in non-melanized hemocytes was recorded as compared to the control. A strong decrease in melanization at 50 ppm and an increase at 50 and 1000 ppm in non-melanized bead count at 24 h were also observed. It can be concluded that IAA is inappropriate to use in combination with microbial control agents in IPM programs due to elevated hemocyte counts of the pest.