Types Of Hemocytes Research Articles

Phagocytic activities of hemocytes from the deep-sea symbiotic mussels Bathymodiolus japonicus, B. platifrons, and B. septemdierum

Deep-sea mytilid mussels harbor symbiotic bacteria in their gill epithelial cells that are horizontally or environmentally transmitted to the next generation of hosts. To understand the immune defense system in deep-sea symbiotic mussels, we examined the hemocyte populations of the symbiotic Bathymodiolus mussel species Bathymodiolus japonicus, Bathymodiolus platifrons, and Bathymodiolus septemdierum, and characterized three types of hemocytes: agranulocytes (AGs), basophilic granulocytes (BGs), and eosinophilic granulocytes (EGs). Of these, the EG cells were the largest (diameter, 8.4–10.0 μm) and had eosinophilic cytoplasm with numerous eosinophilic granules (diameter, 0.8–1.2 μm). Meanwhile, the BGs were of medium size (diameter, 6.7–8.0 μm) and contained small basophilic granules (diameter, 0.3–0.4 μm) in basophilic cytoplasm, and the AGs, the smallest of the hemocytes (diameter, 4.8–6.0 μm), had basophilic cytoplasm lacking granules. A lectin binding assay revealed that concanavalin A bound to all three hemocyte types, while wheat germ agglutinin bound exclusively to EGs and BGs. The total hemocyte population densities within the hemolymph of all three Bathymodiolus mussel species were similar (8.4–13.3 × 105 cells/mL), and the percentages of circulating AGs, BGs, and EGs in the hemolymph of these organisms were 44.7–48.5%, 14.3–17.6%, and 34.3–41.0%, respectively. To analyze the functional differences between these hemocytes, the phagocytic activity and post-phagocytic phagosome–lysosome fusion events were analyzed in each cell type using a fluorescent Alexa Fluor® 488-conjugated Escherichia coli bioparticle and a LysoTracker® lysosomal marker, respectively. While the AGs exhibited no phagocytic activity, both types of granulocytes were phagocytic. Of the three hemocyte types, the EGs exhibited the highest level of phagocytic activity as well as rapid phagosome–lysosome fusion, which occurred within 2 h of incubation. Meanwhile, the BGs showed lower phagocytic activity and lower rates of phagosome–lysosome fusion than the EGs. These findings indicate that the two types of granulocyte play distinct roles in the defense system.

Morphology and Immune-related activities of hemocytes of the mussel Mytilus coruscus (Gould, 1861) from East Sea of Korea

Mytilus coruscus is a cold water mussel commonly occurring on shallow subtidal rocky substrata along the east coast of Korea. Despite its abundance, there have only been a few studies conducted reporting on its biology and ecology. In this study, we investigated the immune-related activities of hemocytes of M. coruscus using light microscopy and flow cytometry. Based on the morphology and cellular activities, 3 types of hemocytes were identified, as granulocytes, hyalinocytes, and blast-like cells. Granulocytes, containing numerous intra-cytoplasmic granules, were intermediate-size (11.8μm) and the most abundant cells (70.2%), while hyalinocytes were the largest cells (16.0μm), with no or few granules in their cytoplasm. The granulocytes exhibited higher lysosomal content, phagocytosis activity and oxidative capacities than the hyalinocytes. In contrast, the blast-like cells were the smallest cells (6.4μm) and displayed a lack of phagocytosis and oxidative capacities. In M. coruscus, the granulocytes appear as the major cell type involved in cellular defense, whereas the blast-like cells may not be directly involved in cell-mediated immune response.

Drosophila sessile hemocyte clusters are true hematopoietic tissues that regulate larval blood cell differentiation.

Virtually all species of coelomate animals contain blood cells that display a division of labor necessary for homeostasis. This functional partition depends upon the balance between proliferation and differentiation mostly accomplished in the hematopoietic organs. In Drosophila melanogaster, the lymph gland produces plasmatocytes and crystal cells that are not released until pupariation. Yet, throughout larval development, both hemocyte types increase in numbers. Mature plasmatocytes can proliferate but it is not known if crystal cell numbers increase by self-renewal or by de novo differentiation. We show that new crystal cells in third instar larvae originate through a Notch-dependent process of plasmatocyte transdifferentiation. This process occurs in the sessile clusters and is contingent upon the integrity of these structures. The existence of this hematopoietic tissue, relying on structure-dependent signaling events to promote blood homeostasis, creates a new paradigm for addressing outstanding questions in Drosophila hematopoiesis and establishing further parallels with vertebrate systems.

Immune challenges trigger cellular and humoral responses in adults of Pterostichus melas italicus (Coleoptera, Carabidae)

The present study focuses on the ability of Pterostichus melas italicus Dejean to mount cellular and humoral immune responses against invading pathogens. Ultrastructural analyses revealed the presence of five morphologically distinct types of hemocytes: prohemocytes, plasmatocytes, granulocytes, oenocytoids and macrophage-like cells. Differential hemocyte counts showed that plasmatocytes and granulocytes were the most abundant circulating cell types and plasmatocytes exhibited phagocytic activity following the latex bead immune challenge. Macrophage-like cells were recruited after the immune challenge to remove exhausted phagocytizing cells, apoptotic cells and melanotic capsules formed to immobilize the latex beads. Total hemocyte counts showed a significant reduction of hemocytes after latex bead treatment. Phenoloxidase (PO) assays revealed an increase of total PO in hemolymph after immune system activation with lipopolysaccharide (LPS). Moreover, the LPS-stimulated hemocytes showed increased protein expression of inducible nitric oxide synthase, indicating that the cytotoxic action of nitric oxide was engaged in this antimicrobial collaborative response. These results provide a knowledge base for further studies on the sensitivity of the P. melas italicus immune system to the environmental perturbation in order to evaluate the effect of chemicals on non-target species in agroecosystems.

Blood Cells Morphology of the SnailBellamya Bengalensis

Morphological characters of haemocytes and seasonal changes in blood indices were studied in Bellamya bengalensis. Two types of haemocytes were identified: I (Ia and Ib) and II. Spherical type I haemocytes (ca. 93%) are cells capable of spread-ing on the substratum and forming numerous pseu-dopodia. Subtypes Ia and Ib are most probably two different development stages of the same cell type. Type II haemocytes are oval cells of stable shape, rarely forming pseudopodia. A wide individual var-iation and significant seasonal changes were found, involving the number of haemocytes and haemato-logical indices.

Морфофизиологические особенности гемоцитов моллюска-интродуцента Stenomphalia ravergieri

Features of formed elements of the haemolymph of mollusc Stenomphalia ravergieri are shown. Four types of haemocytes have been identified. Spherical haemocytes of the first type are capable of spreading and the formation of multiple pseudopodia that allows them to participate actively in phagocytic reactions. Haemocytes of type 2 are oval cells of the steady form which seldom form pseudopodia, they can adhere alien objects on their surface. Haemocytes of type 3 are amorphous cells of small size, with small pseudopodia. Haemocytes of type 4 differ from the previous type of cells in size only, and, probably, are an intermediate phase of the development of the third type haemocytes. Individual changes in the structure of cellular populations and dynamics of the number of haemocytes are revealed..

Effects of the pyrethroid insecticide deltamethrin on the hemocytes of Galleria mellonella

In the present study, the effects of deltamethrin on cell-mediated immune response and genotoxic damage of Galleria mellonella (Lepidoptera: Pyralidae) were investigated. Different concentrations of deltamethrin (5, 20, 50, 100, and 150 µg) were administered to G. mellonella at 24, 48, 72, and 96 h. Five types of hemocytes were identified in G. mellonella: prohemocytes, plasmatocytes, granulocytes, spherulocytes, and oenocytes. Total hemocyte counts (THCs) were significantly affected by deltamethrin. At 72 h, THCs of the treated group had significantly decreased compared with the control groups at high deltamethrin concentrations (50, 100, and 150 µg); however, at 96 h, THCs had significantly increased at deltamethrin concentrations of 100 and 150 µg. Micronucleus formation was significantly affected by deltamethrin; in particular, high concentrations of deltamethrin (100 and 150 µg) caused an increase in micronucleus formation at all time points. We conclude that deltamethrin affected THCs and caused the induction of micronucleus formation via genotoxic damage in G. mellonella.

A first insight into haemocytes of the smooth venus clam Callista chione

The smooth venus clam Callista chione is a commercially exploited bivalve species that lives on the sandy bottom of the Italian coast of the Northern Adriatic Sea. Currently, no information is available in the literature about the haemocytes of this bivalve species. In this study, we performed a morpho-functional characterisation of the haemocytes of C. chione. In freshly collected haemocytes, the total haemocyte count (THC) (measured by a Coulter Counter) varied markedly among individuals, and the mean number of haemocytes was 1.2 (×106) cells mL haemolymph−1. The mean values for the haemocyte diameter and volume were 4.2 μm and 77.8 fL, respectively. In some cases, higher THC values were related to a smaller haemocyte size, but no correlation was detected between the THC and haemocyte diameter or between THC and cell volume. Conversely, a positive correlation was observed between cell diameter and volume. Two haemocyte types were distinguished by light microscopy: granulocytes (76%), with evident cytoplasmic granules, and hyalinocytes (24%), with a few or no granules. After adhesion to slides and fixation, the cell diameter was approximately 10 μm for granulocytes and 7 μm for hyalinocytes. The granules of the granulocytes were stained in vivo with Neutral Red, indicating that they were lysosomes. The granulocytes and hyalinocytes were further distinguished as basophils and acidophils. Both the granulocytes and the hyalinocytes were able to phagocytise yeast cells. Of 2643 cells that were counted, 2007 (76%) showed phagocytic activity. The granulocytes and hyalinocytes were both positive for some hydrolytic enzymes, whereas they were not positive for peroxidase or phenoloxidase. The two types of haemocytes also produced superoxide anion. Overall, this preliminary study indicates that both the granulocytes and hyalinocytes of C. chione are immune effector cells.

ROLE OF POLLEN AND/OR BEE BREAD AVAILABILITY IN BROOD REARING AND CELLULAR IMMUNE SYSTEM OF HONEYBEES

The role of pollen and/or bee bread availability was evaluated on brood rearing, protein content and haemolymph of 6-days-old larvae worker honeybees. The highest area of stored pollen and/or bee bread and worker unsealed brood was recorded during August with an average 157.7±24.701 and 347.7±51.348 (sq. inch / Colony), respectively. Highly significant positive correlation was detected between stored pollen and/or bee bread and worker unsealed brood (r = 0.902**). Physiological studies on larvae and their haemolymph indicated that the, lowest protein content of both larvae and their haemolymph 22.03±6.325 % and 4.04±0.48 (µg/µl), respectively was found during April. Significant positive correlation was noticed between stored pollen and/or bee bread from one side and both larval protein content and haemolymph protein content on the other hand, (r = 0.393* and 0.345*), respectively. The highest of both total soluble solids (TSS %) and total haemocyte count (THC) was found during May and January. On the other hand, the lowest average of both (TSS %) and (THC) was noticed during April. Differential haemocytes counts (DHC) were counted in smears of their haemolymph. There were significant differences in different haemocyte types among various months. So, it turns out previously, it can be recommended for special attention protein nutrition artificially by providing nutrition supplements or pollen substitutes for bee colonies and that in periods of scarcity or lack of pollen as well as in the periods of disease spreads. In this process the chances of incidence of disease can be reduced and improve the immune system of bees. This is in addition to reducing the loss incident in bee colonies as a result of starvation.

Effect of an entomopathogenic nematode, Steinernema carpocapsae on haemocyte profile and phenoloxidase activity of the Colorado potato beetle, Leptinotarsa decemlineata

The Colorado potato beetle (CPB), Leptinotarsa decemlineata Say is the most destructive insect pest of potato in many areas of the world. Little is known about the haemocyte types of the CPB and its plasma phenoloxidase (PO). In this regard, we investigated the haemocyte profile and PO of CPB and its immune response to the entomopathogenic nematode, Steinernema carpocapsae. Five types of haemocytes, the plasmatocytes (~67.4%), granulocytes (~23.5%), oenocytoids (~2.4%), spherulocytes (~0.25%) and prohaemocytes (~6.5%) were identified in fourth instar CPB larvae. Total haemocyte counts (THCs) were significantly reduced in nematode-injected insects compared with control groups (P < 0.05). Nematode cellular encapsulation observed in haemolymph of nematode-injected insects may partially explain decreased THCs. Plasma PO assay showed increased PO activity in nematode-injected insects compared with control groups (P < 0.05). Plasma PO assay on native polyacrylamide gel electrophoresis (PAGE) assay with L-3, 4-dihydroxyphenylalanine as substrate showed five bands (with molecular weights of approximately 200, 118, 68.5, 62.5 and 58.75 kDa).

A comparative study of haemocytes in three cyclorrhaphous dipteran flies

The larval haemolymph of three cyclorrhaphous dipteran flies, Sarcophaga ruficornis Fab., Musca domestica L. and Chrysomya megacephala Fab., possesses five different types of haemocytes: prohaemocytes; plasmatocytes; granulocytes; spherulocytes; oenocytoids. In addition, vermicytes are found in the haemolymph of S. ruficornis and adipohaemocytes in the haemolymph of M. domestica. The total haemocyte counts in the three dipteran flies show an increasing trend throughout the larval stage, attaining a peak value in the freshly formed white puparium stage and declining thereafter. The differential haemocyte count shows a decline in the number of prohaemocytes with an increase in the number of plasmatocytes, granulocytes and spherulocytes.

Characterization of the hemocytes in Larvae of Protaetia brevitarsis seulensis: involvement of granulocyte-mediated phagocytosis.

Hemocytes are key players in the immune response against pathogens in insects. However, the hemocyte types and their functions in the white-spotted flower chafers, Protaetia brevitarsis seulensis (Kolbe), are not known. In this study, we used various microscopes, molecular probes, and flow cytometric analyses to characterize the hemocytes in P. brevitarsis seulensis. The circulating hemocytes were classified based on their size, morphology, and dye-staining properties into six types, including granulocytes, plasmatocytes, oenocytoids, spherulocytes, prohemocytes, and adipohemocytes. The percentages of circulating hemocyte types were as follows: 13% granulocytes, 20% plasmatocytes, 1% oenocytoids, 5% spherulocytes, 17% prohemocytes, and 44% adipohemocytes. Next, we identified the professional phagocytes, granulocytes, which mediate encapsulation and phagocytosis of pathogens. The granulocytes were immunologically or morphologically activated and phagocytosed potentially hazardous substances in vivo. In addition, we showed that the phagocytosis by granulocytes is associated with autophagy, and that the activation of autophagy could be an efficient way to eliminate pathogens in this system. We also observed a high accumulation of autophagic vacuoles in activated granulocytes, which altered their shape and led to autophagic cell death. Finally, the granulocytes underwent mitotic division thus maintaining their number in vivo.

Classification and phagocytosis of circulating haemocytes in Chinese mitten crab (Eriocheir sinensis) and the effect of extrinsic stimulation on circulating haemocytes in vivo

Eriocheir sinensis (Henri Milne Edwards 1854) is one of the most important aquaculture species in China. In this investigation, we characterised the different types of haemocytes of E. sinensis using light and electron microscopy combined with cytochemical analysis and determined the in vivo phagocytic ability of different haemocyte types by injecting polystyrene beads. The haemocytes of E. sinensis were divided into three types: hyalinocytes, semigranulocytes and granulocytes. The hyalinocytes had no or few cytoplasmic granules; the semigranulocytes contained abundant small granules and a few large refractile cytoplasmic granules; and the granulocytes contained numerous large refractile cytoplasmic granules. The hyalinocytes were demonstrated to be the most abundant circulating haemocytes and the most avid phagocytic haemocytes, accounting for approximately 88.7% of the total phagocytes. The haemocyte-containing granules displayed limited phagocytic ability, with approximately 5.0% of granulocytes and 6.3% of semigranulocytes displaying positive phagocytic ability against the invading polystyrene beads in vivo. After injection with Aeromonas hydrophila, Bacillus subtilis and different concentrations of lipopolysaccharide for 0.25, 0.5, 1, 2, 4, 6 and 8 h, all three types of haemocytes experienced dramatic decline and then rapid recovery to their initial levels. A high concentration of lipopolysaccharide and A. hydrophila were extremely toxic to the crabs, as they induced a more serious loss of haemocytes compared with a low concentration of lipopolysaccharide and B. subtilis. Overall, the results obtained in this study indicate that a small proportion of the haemocytes of E. sinensis contributed to the phagocytic process, and the migration of haemocytes and haemocyte lysis were most likely a prominent pathway for pathogen elimination.

Hemócitos de Bradybaena similaris e Megalobulimus abbreviatus (Gastropoda, Stylommatophora)

Os hemócitos atuam no sistema de defesa contra organismos invasores e partículas estranhas, auxiliando o reconhecimento do que é próprio do corpo dos grastrópodes e o que não é. São escassas as informações e estudos sobre os hemócitos em espécies de moluscos saudáveis (sem infecções), principalmente em Bradybaena similaris (Fèrussac, 1821) and Megalobulimus abbreviatus (Bequaert, 1948). Portanto, este trabalho tem como objetivos a caracterização e quantificação dos hemócitos presentes na hemolinfa destas duas espécies. Neste trabalho, foram identificados três tipos celulares na hemolinfa de ambas espécies: as células redondas, hialinócitos e granulócitos. Os três tipos de hemócitos foram medidos e foi calculada a média do diâmetro total e do núcleo para cada um deles. Para B. similaris, o diâmetro médio das células redondas foi de 10,7 µm, dos hialinócitos foi de 20 µm e dos granulócitos de 25,4 µm. Para M. abbreviatus, o diâmetro médio foi de 11,7 µm para as células redondas, de 21,5 µm para os hialinócitos e de 30,5 µm para os granulócitos. Embora os hialinócitos possuam médias parecidas entre B. similaris e M. abbreviatus, foram detectadas diferenças significativas do diâmetro celular total e diâmetro do núcleo (p&lt;0,0001) dessas células entre as espécies estudadas. A densidade média de células por ml, sem distinção de tipo celular foi de 197.813 células/ml para M. abbreviatus, e de 416.333 células/ml para B. similaris. Diferentemente de outros gastrópodes, os hemócitos mais frequentes em M. abbreviatus e em B. similaris foram os hialinócitos.

Quantitative and ultrastructural changes in the haemocytes of Spodoptera littoralis (Boisd.) treated individually or in combination with Spodoptera littoralis multicapsid nucleopolyhedrovirus (SpliMNPV) and azadirachtin

The total haemocyte count (THC) and the possible ultrastructural alterations induced in the haemocytes of the fourth larval instars of the Egyptian cotton leafworm, Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae), 96h post-feeding on a semi-synthetic diet, treated with the LC50 of Spodoptera littoralis multicapsid nucleopolyhedrovirus (SpliMNPV) and the LC50 of azadirachtin alone, and the LC25 of SpliMNPV combined with the LC25 of azadirachtin were studied and compared to the control. Single treatment with the virus and azadirachtin or combined treatment significantly decreased the THC compared to the control. There are five types of haemocytes in S. littoralis: prohaemocytes, plasmatocytes, granulocytes, spherulocytes and oenocytoids. The most common symptoms in granulocytes and plasmatocytes, the main affected cell types, due to viral infection were the presence of virogenic stroma, peripheral dispersion of the chromatin and disappearance of the nucleoli. However, the most common symptoms in these two types of haemocytes due to treatment with azadirachtin were the presence of rough endoplasmic reticulum filled with fibrous materials, due to probably apoptosis, in their cisternae and disorganization of mitochondria (looped, vacuolated and swollen). In addition, the cytoplasm of granulocytes was vacuolated with the appearance of autophagic lysosomes, while plasmatocytes showed ruptured cell membrane and folded nuclear envelope. Combined treatment with the NPV and azadirachtin induced the same pathological changes which were recorded from individual treatment with the virus or azadirachtin to the same haemocytes. It can be concluded that the change in the THC and ultrastructure of granulocytes and plasmatocytes may affect the cellular-mediated immune response in S. littoralis. Moreover, it seems likely that mitochondria were the target site of azadirachtin, as they were affected in both granulocytes and plasmatocytes treated with azadirachtin alone or in combination with SpliMNPV.

PmVRP15, a novel viral responsive protein from the black tiger shrimp, Penaeus monodon, promoted white spot syndrome virus replication.

Suppression subtractive hybridization of Penaeus monodon hemocytes challenged with white spot syndrome virus (WSSV) has identified the viral responsive gene, PmVRP15, as the highest up-regulated gene ever reported in shrimps. Expression analysis by quantitative real time RT-PCR revealed 9410–fold up-regulated level at 48 h post WSSV injection. Tissue distribution analysis showed that PmVRP15 transcript was mainly expressed in the hemocytes of shrimp. The full-length cDNA of PmVRP15 transcript was obtained and showed no significant similarity to any known gene in the GenBank database. The predicted open reading frame of PmVRP15 encodes for a deduced 137 amino acid protein containing a putative transmembrane helix. Immunofluorescent localization of the PmVRP15 protein revealed it accumulated around the nuclear membrane in all three types of shrimp hemocytes and that the protein was highly up-regulated in WSSV-infected shrimps. Double-stranded RNA interference-mediated gene silencing of PmVRP15 in P. monodon significantly decreased WSSV propagation compared to the control shrimps (injected with GFP dsRNA). The significant decrease in cumulative mortality rate of WSSV-infected shrimp following PmVRP15 knockdown was observed. These results suggest that PmVRP15 is likely to be a nuclear membrane protein and that it acts as a part of WSSV propagation pathway.

Apis mellifera hemocytes generate increased amounts of nitric oxide in response to wounding/encapsulation

Apis mellifera populations are being threatened by several pathogens and parasitosis. Several authors have proposed that honey bee colonies may suffer from a compromised immune system leading to colony loss. This is why the study of A. mellifera immune system has become a topic of pressing concern. Nitric oxide (NO) is a signaling and immune effector molecule that has been proposed as a key molecule in invertebrate immunity, and that plays a part in A. mellifera cellular defenses. This paper deals with NO participation in the response to wounding/encapsulation challenge in A. mellifera fifth instar (L5) larvae. Challenging A. mellifera L5 larvae with nylon implants enhanced NO production and spreading in granulocyte-like hemocytes and increased the number of this NO-producing hemocyte type. However, AmNOS expression levels were not influenced by the insult. These results reveal that NO participates in the wound healing/encapsulation response as a signal molecule, possibly by the activation of a constitutively expressed AmNOS in honey bees.

Cellular reactions of the white grub larvae, Polyphylla adspersa, against entomopathogenic nematodes

The haemocyte reactions of the white grub larvaePolyphylla adspersato entomopathogenic nematodes (EPN), together with the host haemocyte types, have been studied. Six types of identified haemocytes included the prohaemocytes, granulocytes, plasmatocytes, oenocytoids, coagulocytes and spherulocytes. The granulocytes were the dominant (65.2%) haemocyte type followed by the plasmatocytes (22.1%). Both haemocyte types encapsulate EPN. White grub larvae and last larval stage ofGalleria mellonellawere individually infected with monoxenicHeterorhabditis bacteriophoraorSteinernema glaseri. The maximum total haemocyte counts (THC) level of the white grub larvae against the nematodeS. glaserioccurred at 12 h post-injection. In addition, by 8 h post-injection, the granulocyte and plasmatocyte levels decreased. The cell reactions of the grubs againstH. bacteriophorain terms of THC and differential haemocyte counts and the encapsulation rate started earlier and were more pronounced than those againstS. glaseri. The maximum percentage of the encapsulation observed in the white grub larvae againstS. glaseri(27.3 ± 0.7%) andH. bacteriophora(36.5 ± 3.5%) occurred at 12 and 8 h post-injection, respectively. EPN-triggered encapsulation inP. adspersalarvae was more extensive than inG. mellonellalarvae.

Ultrastructure changes in the haemocytes of Galleria mellonella larvae treated with gamma irradiated Steinernema carpocapsae BA2

The ultrastructure studies on the haemolymph of 5th larval instar of Galleria mellonella showed five types of haemocytes; Prohaemocytes, Plasmatocytes, Granulocytes, Oenocytoids and Spherulocytes. After treatment with Steinernema carpocapsae BA2, the haemocytes underwent considerable structural changes. More destructive effects were observed in the haemocytes of G. mellonella treated with gamma irradiated S. carpocapsae.

Drosophila as a model to study the role of blood cells in inflammation, innate immunity and cancer

Drosophila has a primitive yet effective blood system with three types of haemocytes which function throughout different developmental stages and environmental stimuli. Haemocytes play essential roles in tissue modeling during embryogenesis and morphogenesis, and also in innate immunity. The open circulatory system of Drosophila makes haemocytes ideal signal mediators to cells and tissues in response to events such as infection and wounding. The application of recently developed and sophisticated genetic tools to the relatively simple genome of Drosophila has made the fly a popular system for modeling human tumorigensis and metastasis. Drosophila is now used for screening and investigation of genes implicated in human leukemia and also in modeling development of solid tumors. This second line of research offers promising opportunities to determine the seemingly conflicting roles of blood cells in tumor progression and invasion. This review provides an overview of the signaling pathways conserved in Drosophila during haematopoiesis, haemostasis, innate immunity, wound healing and inflammation. We also review the most recent progress in the use of Drosophila as a cancer research model with an emphasis on the roles haemocytes can play in various cancer models and in the links between inflammation and cancer.