A hemocyte is a
cell
Cell most often refers to:
* Cell (biology), the functional basic unit of life
Cell may also refer to:
Locations
* Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery ...
that plays a role in the
immune system
The immune system is a network of biological processes that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as cancer cells and objects such as wood splinte ...
of
invertebrates
Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordat ...
. It is found within the
hemolymph
Hemolymph, or haemolymph, is a fluid, analogous to the blood in vertebrates, that circulates in the interior of the arthropod (invertebrate) body, remaining in direct contact with the animal's tissues. It is composed of a fluid plasma in which ...
.
Hemocytes are
phagocyte
Phagocytes are cells that protect the body by ingesting harmful foreign particles, bacteria, and dead or dying cells. Their name comes from the Greek ', "to eat" or "devour", and "-cyte", the suffix in biology denoting "cell", from the Greek ...
s of invertebrates.
Hemocytes in ''
Drosophila melanogaster
''Drosophila melanogaster'' is a species of fly (the taxonomic order Diptera) in the family Drosophilidae. The species is often referred to as the fruit fly or lesser fruit fly, or less commonly the " vinegar fly" or "pomace fly". Starting with ...
'' can be divided into two categories: embryonic and larval. Embryonic hemocytes are derived from head
mesoderm
The mesoderm is the middle layer of the three germ layers that develops during gastrulation in the very early development of the embryo of most animals. The outer layer is the ectoderm, and the inner layer is the endoderm.Langman's Medical Emb ...
and enter the hemolymph as circulating cells. Larval hemocytes, on the other hand, are responsible for tissue remodeling during development. Specifically, they are released during the pupa stage in order to prepare the fly for the transition into an adult and the massive associated tissue reorganization that must occur.
There are four basic types of hemocytes found in fruit flies: secretory, plasmatocytes, crystal cells, and lamellocytes. Secretory cells are never released into the hemolymph and instead send out signalling molecules responsible for cell differentiation. Plasmatocytes are the hemocytes responsible for cell ingestion (phagocytosis) and represent about 95% of circulating hemocytes. Crystal cells are only found in the larval stage of Drosophila, and they are involved in melanization, a process by which microbes/pathogens are engulfed in a hardened gel and destroyed via anti-microbial peptides and other proteins involved in the humoral response. They constitute about 5% of circulating hemocytes. Lamellocytes are flat cells that are never found in adult cells, and instead are only present in larval cells for their ability to encapsulate invading pathogens. They specifically act on parasitic wasp eggs that bind to the surfaces of cells, and are incapable of being phagocytosed by host cells.
In
mosquito
Mosquitoes (or mosquitos) are members of a group of almost 3,600 species of small flies within the family Culicidae (from the Latin ''culex'' meaning " gnat"). The word "mosquito" (formed by ''mosca'' and diminutive ''-ito'') is Spanish for "li ...
es, hemocytes are functionally divided into three populations: granulocytes, oenocytoids and prohemocytes.
Granulocytes are the most abundant cell type. They rapidly attach to foreign surfaces and readily engage in
phagocytosis
Phagocytosis () is the process by which a cell uses its plasma membrane to engulf a large particle (≥ 0.5 μm), giving rise to an internal compartment called the phagosome. It is one type of endocytosis. A cell that performs phagocytosis is ...
. Oenocytoids do not readily spread on foreign surfaces and are the major producers of phenoloxidase, which is the major enzyme of the melanization immune pathway. Prohemocytes are small cells of unknown function, which may result from the asymmetric mitosis of granulocytes.
References
External links
*
Immunology
Blood cells
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