Activation of the immune system either by administration of a vaccine that contains a modified antigen or exposure to the antigen (e.g., disease)
The primary type of hemoglobin found in red blood cells of animals beginning a couple of weeks to a couple of months after birth.
Precipitation or clumping of antigen-antibody complexes; one of the methods by which the immune system neutralizes antigens.
Decreased oxygen-carrying capacity of the blood caused by insufficient numbers of red blood cells, decreased hemoglobin concentration, or a combination of these conditions.
Proteins produced by plasma cells (transformed B lymphocytes) in response to the presence of an antigen; a specific serum antibody is produced for a specific antigen.
Cells or organisms that are "not self". Can also be a structure on a cell membrane that the body recognizes as foreign. Initiates an immune response in a healthy animal.
An abnormal condition in which the body starts recognizing some of its own cells as "non self" and initiates an immune response to destroy them.
The type of lymphocyte that is responsible for humoral immunity through its transformation into a plasma cell and production of antibodies.
One of the granulocytic white blood cells characterized by the presence of numerous, dark blue staining granules in its cytoplasm.
Through this process, B lymphocytes become plasma cells that produce antibodies.
The portion of the immune system that produces "killer" cells that directly attack foreign invaders.
The movement of white blood cells into an area of inflammation in response to chemical mediators released at the site by injured tissue or other white blood cells.
Microscopic particles of fat found in chyle and blood; their numbers are highest after a meal.
Circulating Pool of Neutrophils
Neutrophils found in the peripheral blood flowing through the center of the blood vessel.
The initial secretion of the mammary gland before milk is produced; rich in nutrients, has a laxative effect in the newborn, and contains antibodies to diseases the dam has been exposed to or vaccinated against. If consumed within a few hours of birth, the intact antibodies are absorbed through the intestine to confer passive immunity to the animal.
A large group of inactive enzymes (proteins) found in plasma that can be activated to rupture the cell membrane of a foreign cell. Can also act as an opsonin.
Cytotoxic T Cells
Also known as killer cells or killer T lymphocytes; they attach to antigenic cells and destroy them, but they are not themselves damaged.
The process by which white blood cells leave the blood vessel and enter tissue by squeezing through the tiny spaces between the cells lining the blood vessel walls.
An abnormal accumulation of fluid, either local or generalized, within the tissues or cavities of the body.
An increase in the total number of of eosinophils in peripheral blood; frequently associated with allergic conditions or parasites.
The granulocytic white blood cell characterized by the presence of numerous red-staining, acidic granules in the cytoplasm.
Also called red blood cells, these cells are anucleated (in mammals) and biconcave in shape; they are responsible for carrying oxygen from the lungs to tissue. These cells are formed in the red bone marrow of adults and in the liver, spleen, and marrow of the fetus.
Hormone produced by the kidney that stimulates the red bone marrow to increase its production of red blood cells in response to hypoxia.
The predominant hemoglobin in red blood cells during the later part of gestation; it is gradually replaced by adult hemoglobin during the first few weeks to months after birth.
A protein created when thrombin acts on fibrinogen; essential to the coagulation of blood. It forms a lattice of interwoven fibers around blood cells and platelets that solidify to form a blood clot.
A protein formed in the liver and released into the bloodstream, especially in the presence of inflammatory processes. Fibrinogen, when acted on by thrombin, forms fibrin, which creates the meshwork of a blood clot.
Destruction of the fibrin strands that make up the matrix of a clot; part of the process of the breakdown of a clot.
White blood cells that are characterized by the presence of granules in their cytoplasm; includes neutrophils, eosinophils, and basophils.
Gut Associated Lymphoid Tissue
Lymphoid tissue scattered throughout the lining of the intestine; it is often compared with the bursa of Fabricius in birds, where B lymphocytes are processed. Abbreviated GALT.
A transport plasma protein that carries free hemoglobin from intravascular hemolysis to the macrophages of the mononuclear phagocyte system in the liver for further breakdown.
Helper T Cells
The most numerous of the T lymphocytes; they help the immune response by secreting substances known as lymphokines into the surrounding tissue, which increases the activation of B lymphocytes and cytotoxic T cells.
The percentage of a total blood sample volume made up of red blood cells; also known as the packed cell volume.
A condition resulting from a loss of plasma from blood into tissue; the cells become more concentrated in the plasma, increasing the PCV. This is seen in dehydrated animals.
A condition resulting from excess fluid entering blood from tissue or from intravenous injection of fluids; the cells become more diluted in plasma, decreasing the PCV. This condition can result from overhydration with IV or SQ fluids.
The protein molecules found inside red blood cells that are responsible for carrying oxygen molecules.
Hemoglobin in the plasma; the RBC membrane has ruptured, resulting in the release of hemoglobin. Results from intravascular hemolysis.
Free hemoglobin found in the urine; the degree of intravascular hemolysis was great enough to release large amounts of hemoglobin. Excess hemoglobin not handled by haptoglobin is eliminated in the urine.
A type of defense immune response regulated by B lymphocytes; when B lymphocytes are activated by the presence of an antigen, they transform into plasma cells that produce antibodies against the antigen.
A neutrophil that has more than five nuclear lobes when seen in peripheral blood.
The yellowish color given to tissues, membranes, and secretions by the presence of bile pigments; may indicate elevated levels of bilirubin, possibly resulting from liver failure. Also known as jaundice.
Immunoglobulin A; it can leave the blood and enter tissue, where it plays an important role in preventing diseases caused by antigens that enter the body through mucosal surfaces.
Immunoglobulin G; it is produced during the first exposure to an antigen and is also made by a newborn animal.
Immunoglobulin M; it is produced after an animal has been exposed to an antigen for an extended time or when an animal is exposed to an antigen for the second time.
Created by B lymphocytes, also called antibodies; these protein-based molecules are produced by exposure to an infectious agent's antigen. In future encounters with the same antigen, these molecules will identify and fight it.
A substance produced by a cell after a virus has invaded it; prevents further development or spread of the virus.
"White blood"; a cancer or malignancy of one type of white blood cells. Production of that type of cell is abnormal and uncontrolled.
Also called white blood cells; includes neutrophils, eosinophils, basophils, monocytes, and lymphocytes. Their main function is body defense.
Nongranulocytic white blood cells that are involved in the immune response; the two types are T lymphocytes (cell-mediated immunity) and B lymphocytes (humoral immunity). Predominant leukocytes in pigs and ruminants.
Proteins that develop on the surface of helper T lymphocytes; they activate killer T lymphocytes, which are responsible for cell-mediated immunity.
Phagocytic cells that can engulf relatively large cells or bits of debris; may be fixed in place or travel around in the tissues. Mature cells become more mobile during times of infection and inflammation.
Marginal Pool of Neutrophils
Neutrophils found lining the walls of small blood vessels, mainly in the spleen, lungs, and abdominal organs; these neutrophils are not circulating, but are moving slowly along the walls of the vessels.
A transient cell of connective tissue containing heparin and histamine used in the inflammatory response; recognize foreign invaders and release granules of histamine and heparin to increase blood flow. They resemble basophils, but they do not circulate in the blood.
Large, multinucleated cells in red bone marrow that are the parent cells of platelets; platelets are formed when chunks of cytoplasm break off a megakaryocyte and enter circulation.
After an initial immune response, lymphocytes that are programmed to remember the antigen that caused the immune response and to produce a more rapid immune response to that antigen the second time the body is exposed to it.
A large phagocytic white blood cell; it is the largest white blood cell found in peripheral blood. It is an agranulocyte.
Mononuclear Phagocyte System
A collective term for monocytes and tissue macrophages found throughout the body.
Natural Killer Cells
Lymphocytes that are neither T lymphocytes or B lymphocytes but have the ability to kill some types of tumor cells and cells infected with various viruses.
A granulocytic white blood cell with a segmented nucleus and clear-staining or neutral granules; phagocytes and known as the first line of defense against invading microorganisms because of their fast response time. Predominant leukocyte in dogs, cats, and horses.
Processes that protect an animal against anything the body recognizes as foreign; it involves inflammation, phagocytosis, and the protective barrier of the skin and mucous membranes, which prevent antigens from entering the body. The immune system is not activated during this response.
Plasma protein, usually an immunoglobulin, that coats an antigen, usually a microorganism, making it more attractive to phagocytes.
The process by which opsonins coat an antigen to make it more susceptible to phagocytosis.
The transmission of intact, preformed antibodies from one animal to another; the antibody molecules can help protect the recipient animal from disease-causing agents. An important source of passive immunity is colostrum ingestion in the newborn.
Blood outside of bone marrow that is flowing to and from the heart and lungs in blood vessels.
A small hemorrhage found on the skin, mucous membranes, and serosal surfaces anywhere in the body.
Ingestion of microorganisms by phagocytic cells (neutrophils, monocytes, and macrophages).
The liquid matrix of blood, which contains proteins and suspended cells; also contains diffused gasses, electrolytes, and a variety of biochemicals.
Also known as thrombocytes; small pieces of cytoplasm that break off megakaryocytes in the bone marrow and enter peripheral blood. They are involved in hemostasis by helping plug leaks in blood vessels and initiating the blood-clotting process.
Various shapes; used to describe a monocyte nucleus that can take on many shapes without dividing into distinct segments.
Pluripotent Stem Cell
Primitive cell type found in red bone marrow; it is the cell type from which all blood cells are formed. Different stimuli act on the PPSC to send it down a particular cell-line pathway; once it starts down a particular path, it is committed to that cell line.
"Many colors"; term used to describe immature red blood cell cytoplasm when it is still metabolically active and has started producing hemoglobin. Results in both red and blue stain being taken up by the cytoplasm, giving it a lavender color.
A condition of cloudy plasma that results from small fat particles found in blood soon after eating.
The term used to describe a nucleus that has died; the chromatin becomes densely compacted, so no pattern is visible.
The fluid portion of blood that has had the clotting factors removed; produced by letting a blood sample clot before the fluid is removed.
Suppressor T Cells
Lymphocytes that inhibit helper T cells and cytotoxic T cells by negative feedback; they also prevent B lymphocytes from transforming into plasma cells. These cells provide the means by which the immune response can be shut down.
A large lymph vessel found in the thorax; it empties its contents of lymph into large blood vessels in the thorax.
Also known as platelets; small pieces of cytoplasm that break off megakaryocytes in the bone marrow and enter peripheral blood. They play a role in hemostasis and the blood clotting process.
An organ that is important in the development of a young animal's immune system; it produces hormone-like substances, such as thymopoietin and thymosin.
The type of lymphocyte that is responsible for cell-mediated immunity; there are three types: helper T cells, cytotoxic T cells, and suppressor T cells.
A clear space in the cytoplasm of a cell; it is surrounded by cell membrane. Phagocytized microorganisms are found in vacuoles.
Yellow Bone Marrow
The most common type of bone marrow found in adult animals; consists mainly of adipose tissue, but can revert to red bone marrow if the body needs greater than normal blood cell production.
Erythrocytes (RBCs) rely on this simple sugar found in the plasma for energy; after hemoglobin production is complete, the mitochondria shut down and are no longer available for energy production.
Vaccine that contains killed virus particles to create an active immune response. Ex: rabies vaccine.
Process where infectious microorganisms are altered so they can no longer produce disease; usually performed for inclusion in "modified live" vaccines, such as the distemper vaccination.