Drosophila melanogaster, the fruit fly, is a model organism widely used in biomedical research thanks to its versatility. Some advantages over other models are its low cost, easy manipulation, short life-cycle and large range of easily performed genetic modifications.

During its approximately 10 days of life cycle, the flies go through an egg embryonic development followed by three instar larvae stages that culminate in pupariating. While at the pupal stage, a metamorphosis takes place and adult flies are formed and ready to gate-crash in your kitchen on a peaceful and warm summer day!

DROSOPHILA MELANOGASTER BLOOD CELLS

One of the fields of application of Drosophila melanogaster is the study of its role in innate immunity.

During embryonic larva-stage, Drosophila blood cells (haemocytes) belong to three lineages: plasmatocytes, crystal cells and lamellocytes. This number of lymphoid lineages is impressive for an insect lacking adaptive immunity!

While lamellocytes are specialised in parasite encapsulation, crystal cells are in charge of melanin production that, together with encapsulation, seem to play a role in killing pathogens. Plasmatocytes are responsible for phagocytosis of invading microbes, repairing damaged tissues and removal of post-apoptotic debris.

PLASMATOCYTES AND CELLULAR IMMUNITY

Analogously to monocytes and macrophages in humans, plasmatocytes undergo phagocytic activity. In systematically infected larvae containing as many as 3000 non-pathogenic bacteria, plasmatocytes have been proved to eliminate up to 95% of the bacterial load in just 30 minutes (Lemaitre, B., et al. 1996)!

Phagocytosis is a necessary and thus evolutionary conserved process that guarantees removal of both apoptotic bodies and invading pathogens. Undeniably, plasmatocytes seem to be effective in ingesting, engulfing and destroying!

There are two pathways of phagocytosis initiation in plasmatocytes: the direct pathway involves specific cell-surface receptors while the indirect pathway encompasses opsonins, which are molecules that mark antigens like microbes in order to make them target of immune response (in this case, phagocytic receptors).

This sample of genetic modification in Drosophila melanogaster represents a good example of its suitability as a model in infection and immunity in biomedical research, but Drosophila is also giving promising results in tumorigenesis and metastasis in cancer research, and in a wide range of research fields, which will certainly contribute to our scientific knowledge.

Bibliography:

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