Kurloff cells (also known as Foà-Kurloff cells,) were described as mononuclear cells in the peripheral blood and organs of the

guinea pig The guinea pig or domestic guinea pig (''Cavia porcellus''), also known as the cavy or domestic cavy (), is a species of rodent belonging to the genus ''Cavia'' in the family Caviidae. Breeders tend to use the word ''cavy'' to describe the ani ...

capybara The capybaraAlso called capivara (in Brazil), capiguara (in Bolivia), chigüire, chigüiro, or fercho (in Colombia and Venezuela), carpincho (in Argentina, Paraguay and Uruguay) and ronsoco (in Peru). or greater capybara (''Hydrochoerus hydro ...

paca A paca is a member of the genus ''Cuniculus'' of ground-dwelling, herbivorous rodents in South and Central America. It is the only genus in the family Cuniculidae. Pacas are large rodents with dots and stripes on their sides, short ears, and ...

agouti The agouti (, ) or common agouti is any of several rodent species of the genus ''Dasyprocta''. They are native to Middle America, northern and central South America, and the southern Lesser Antilles. Some species have also been introduced else ...

and cavie. The Kurloff cell contains a characteristic proteoglycan-containing inclusion body. In the guinea pig, Kurloff cells are more numerous in the adult female than the adult male. A marked increase in the number of circulating Kurloff cells is present in the peripheral blood during pregnancy and after estrogen treatment in male and female animals. A relatively smaller number of cells take place in immature, non-pregnant, and non-estrogen-treated animals. The exact function of Kurloff cells remains unknown, but it has some of the characteristics of both

monocytes Monocytes are a type of leukocyte or white blood cell. They are the largest type of leukocyte in blood and can differentiate into macrophages and conventional dendritic cells. As a part of the vertebrate innate immune system monocytes also infl ...

and

lymphocytes A lymphocyte is a type of white blood cell (leukocyte) in the immune system of most vertebrates. Lymphocytes include natural killer cells (which function in cell-mediated, cytotoxic innate immunity), T cells (for cell-mediated, cytotoxic adap ...

. In guinea-pigs, it has been proposed that Kurloff cells mainly involve in the function of the immune system, such as acting as a

natural killer cell Natural killer cells, also known as NK cells or large granular lymphocytes (LGL), are a type of cytotoxic lymphocyte critical to the innate immune system that belong to the rapidly expanding family of known innate lymphoid cells (ILC) and repres ...

and preventing damage to the

trophoblast The trophoblast (from Greek : to feed; and : germinator) is the outer layer of cells of the blastocyst. Trophoblasts are present four days after fertilization in humans. They provide nutrients to the embryo and develop into a large part of the pl ...

by maternal defensive cells. Also, Kurloff cells present antibody-dependent cytotoxic activity

in vitro ''In vitro'' (meaning in glass, or ''in the glass'') studies are performed with microorganisms, cells, or biological molecules outside their normal biological context. Colloquially called "test-tube experiments", these studies in biology an ...

Structure

The structure of Kurloff cell was identified using

light microscopy Microscopy is the technical field of using microscopes to view objects and areas of objects that cannot be seen with the naked eye (objects that are not within the resolution range of the normal eye). There are three well-known branches of micr ...

and periodic-acid Schiff staining. The Kurloff cell has an egg shape and the axis of the cell varies from 8 to 12 µm in length, and 10-25 µm in diameter. The inclusion body, which is round in shape and 1-8 µm in diameter, occupies most of the cell's

cytoplasm In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. The ...

. Also, the inclusion body resembles a

lymphocyte A lymphocyte is a type of white blood cell (leukocyte) in the immune system of most vertebrates. Lymphocytes include natural killer cells (which function in cell-mediated, cytotoxic innate immunity), T cells (for cell-mediated, cytotoxic ad ...

. The nucleus of Kurloff cell is sickle-shaped and is pushed toward the periphery of the cell by the inclusion body. In

thymus The thymus is a specialized primary lymphoid organ of the immune system. Within the thymus, thymus cell lymphocytes or ''T cells'' mature. T cells are critical to the adaptive immune system, where the body adapts to specific foreign invaders. ...

and

spleen The spleen is an organ found in almost all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter. The word spleen comes .

, Kurloff cells are categorized depending on the size and the number of

inclusion bodies Inclusion bodies are aggregates of specific types of protein found in neurons, a number of tissue cells including red blood cells, bacteria, viruses, and plants. Inclusion bodies of aggregations of multiple proteins are also found in muscle cells ...

within cells. The cells with small and medium-sized inclusions are present when the density of

thymocytes A Thymocyte is an immune cell present in the thymus, before it undergoes transformation into a T cell. Thymocytes are produced as stem cells in the bone marrow and reach the thymus via the blood. Thymopoiesis describes the process which turns thymo ...

is low. On the other hand, cells with large inclusion bodies were first observed among low-density cells. Over time, they are found where the density of

is high.

Tissue distribution

In pregnant and estrogen-treated male and female guinea pigs, clumps of Kurloff cells containing inclusion bodies of different sizes are present in large numbers in stromal tissue of the

and bone marrows, and the pulp cords of the

spleen The spleen is an organ found in almost all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter. The word spleen comes .

. In the thymus, clumps of Kurloff cells are occasionally seen at the cortico-medullary junction, scattered single cells are seen in the cortex, and numerous Kurloff cells are spotted in

lymphatics The lymphatic vessels (or lymph vessels or lymphatics) are thin-walled vessels (tubes), structured like blood vessels, that carry lymph. As part of the lymphatic system, lymph vessels are complementary to the cardiovascular system. Lymph vessel ...

and

venules A venule is a very small blood vessel in the microcirculation that allows blood to return from the capillary beds to drain into the larger blood vessels, the veins. Venules range from 7μm to 1mm in diameter. Veins contain approximately 70% of t ...

. In the spleen, Kurloff cells are absent in the lymphoid tissue of the white pulp, whereas there are large numbers in the red pulp. In the vertebral

bone marrow Bone marrow is a semi-solid tissue found within the spongy (also known as cancellous) portions of bones. In birds and mammals, bone marrow is the primary site of new blood cell production (or haematopoiesis). It is composed of hematopoietic ce ...

, Kurloff cells are seen scattered as single cells and in clumps in random pattern among the

hematopoietic cells Haematopoiesis (, from Greek , 'blood' and 'to make'; also hematopoiesis in American English; sometimes also h(a)emopoiesis) is the formation of blood cellular components. All cellular blood components are derived from haematopoietic stem cells. ...

in the stroma. Besides, the

veins Veins are blood vessels in humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated b ...

and

lymphatic vessels The lymphatic vessels (or lymph vessels or lymphatics) are thin-walled vessels (tubes), structured like blood vessels, that carry lymph. As part of the lymphatic system, lymph vessels are complementary to the cardiovascular system. Lymph vessel ...

of these tissues contain a significantly large number of Kurloff cells relative to the numbers in the

arterial An artery (plural arteries) () is a blood vessel in humans and most animals that takes blood away from the heart to one or more parts of the body (tissues, lungs, brain etc.). Most arteries carry oxygenated blood; the two exceptions are the pul ...

blood supply. It has been suggested that Kurloff cells might be produced at these sites. A small amount of Kurloff cells are observed within

lymph nodes A lymph node, or lymph gland, is a kidney-shaped organ of the lymphatic system and the adaptive immune system. A large number of lymph nodes are linked throughout the body by the lymphatic vessels. They are major sites of lymphocytes that includ ...

, and those which are present are in sinuses and

blood vessels The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away f ...

. During pregnancy and after treatment, a large number of Kurloff cells circulated in the blood. At the placenta of a pregnant guinea pig, Kurloff cells are more concentrated at the vascular channels of the labyrinth than the

plasmodial A plasmodium is a living structure of cytoplasm that contains many nuclei, rather than being divided into individual cells each with a single nucleus. Plasmodia are best known from slime molds, but are also found in parasitic Myxosporea, and so ...

spongy zone

Characteristics

In guinea pig, the Kurloff cells have some characteristics of

and

. The first characteristic that Kurloff cells share with monocytes is the presence in the blood and organ but absence from the

spleen The spleen is an organ found in almost all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter. The word spleen comes .

white pulp, thymus parenchyma, and lymph node follicles. The second shared characteristic is that the Kurloff cell has a receptor for cytophilic

immunoglobin An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...

. On the other hand, Kurloff cells have many lymphocytic features such as it does not contain

lysosomes A lysosome () is a membrane-bound organelle found in many animal cells. They are spherical vesicles that contain hydrolytic enzymes that can break down many kinds of biomolecules. A lysosome has a specific composition, of both its membrane prote ...

phagosomes In cell biology, a phagosome is a Vesicle (biology), vesicle formed around a particle engulfed by a phagocyte via phagocytosis. Professional phagocytes include macrophages, neutrophils, and dendritic cells (DCs). A phagosome is formed by the fus ...

, lack of nonspecific

esterase An esterase is a hydrolase enzyme that splits esters into an acid and an alcohol in a chemical reaction with water called hydrolysis. A wide range of different esterases exist that differ in their substrate specificity, their protein structure, ...

activity, and

phagocytic 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 ...

capacity, and last, the Kurloff cell with the early inclusion body possesses a lymphocyte

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...

. The results of antibody-dependent cellular cytotoxicity assay on guineas-pig Kurloff cells strongly indicate an immunological role of the cells as the

. The data also suggest that the Kurloff cell is probably the predominant cytotoxic line in guinea pig

composition, and different level of killer cell activities depends mostly on varying degrees of Kurloff cell contamination. The Kurloff cells were suggested to have an impact on the immunological status of the guinea-pig placenta. The fate of cells in pregnant guineas pig has been studied by

immunofluorescent Immunofluorescence is a technique used for light microscopy with a fluorescence microscope and is used primarily on microbiological samples. This technique uses the specificity of antibodies to their antigen to target fluorescent dyes to specifi ...

methods, including an antiserum against the isolated

mucoprotein A mucoprotein is a glycoprotein composed primarily of mucopolysaccharides. Mucoproteins can be found throughout the body, including the gastrointestinal tract, reproductive organs, airways, and the synovial fluid of the knees. They are called mucopr ...

of the inclusion body. The satisfactory staining of the inclusion particle was extracted from the

spleen The spleen is an organ found in almost all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter. The word spleen comes .

and

Immunofluorescence Immunofluorescence is a technique used for light microscopy with a fluorescence microscope and is used primarily on microbiological samples. This technique uses the specificity of antibodies to their antigen to target fluorescent dyes to specif ...

results showed that during pregnancy circulating Kurloff cells release their inclusion particles inside the

. In the placenta, the Kurloff cell was occasionally surrounded by a cloud of tiny droplets of material, which gives a similar staining result as the inclusion particles. That material was frequently observed displaying on the luminal surface of the inner placenta compartment. It was obvious that the Kurloff cell must have a role during pregnancy in the guinea-pig because of a significant increase in the number of these cells in the blood and tissues. The inclusion material has been proved to prevent immunological damage to target cells when purified. Studies were done on the effect of extracted inclusion body material in purified form, on inflammatory cells in vitro. The results showed marked toxic effects on macrophages with first clumping follow by cell death. The evidence suggests that Kurloff cells may play a part in preventing immunological damage to the trophoblast by maternal defensive cells.

References

{{Reflist, 30em Blood cells Cavies

Structure

Tissue distribution

Characteristics

See also

References