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Phagocytosis Information and Courses from MediaLab, Inc.

These are the MediaLab courses that cover Phagocytosis and links to relevant pages within the course.

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Laboratories Individuals

CLIA Hematology / Hemostasis Review
Phagocytosis is a function of which of the following types of cells:View Page

CLIA Microbiology / Serology Review
Which of the following substances produced by Group A Streptococci is responsible for producing type specific immunity:View Page

Current Topics in Clinical Microbiology
Review 2

Cunningham MW.: Pathogenesis of group A streptococcal infections. Clinical Microbiology Reviews. 13):470-511, 2000Group A streptococci are model extracellular gram-positive pathogens responsible for pharyngitis, impetigo, rheumatic fever, and acute glomerulonephritis. A resurgence of invasive streptococcal diseases and rheumatic fever has appeared in outbreaks over the past 10 years, with a predominant M1 serotype as well as others identified with the outbreaks.Emm (M protein) gene sequencing has changed serotyping, and new virulence genes and new virulence regulatory networks have been defined. The emm gene superfamily has expanded to include antiphagocytic molecules and immunoglobulin-binding proteins with common structural features.At least nine superantigens have been characterized, all of which may contribute to toxic streptococcal syndrome. An emerging theme is the dichotomy between skin and throat strains in their epidemiology and genetic makeup. Eleven adhesions have been reported, and surface plasmin-binding proteins have been defined.The strong resistance of the group A streptococcus to phagocytosis is related to factor H and fibrinogen binding by M protein and to disarming complement component C5a by the C5a peptidase. Molecular mimicry appears to play a role in autoimmune mechanisms involved in rheumatic fever, while nephritis strain-associated proteins may lead to immune-mediated acute glomerulonephritis. Vaccine strategies have focused on recombinant M protein and C5a peptidase vaccines, and mucosal vaccine delivery systems are under investigation.

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Factors related to the strong resistance of certain strains of group A streptococci to phagocytosis include:View Page

Mycology: Yeasts and Dimorphic Pathogens
Each of the following is considered to be a virulence factor in Cryptococcus neoformans except:View Page

Normal Peripheral Blood Cells
Match the characteristics with the cells.View Page
Glossary of Terms N through Z.

N:C Ratio - Nuclear: cytoplasmic Ratio - The ratio of nuclear volume to cytoplasmic volume within any one cell.Neoplasm - Any new and abnormal growth, such as a tumor.Neutrophilic Granules - Specific granules present in the cytoplasm of neutrophils. These granules resemble pencil stippling and stain a lilac color due to their affinity for both basic and acid dyes.Phagocyte - Any cell that ingests microorganisms or other cells and foreign particles.Phagocytosis - The ingestion and destruction of microorganisms or other foreign particles.Plasma - The fluid portion of blood in which the various blood cells are suspended.PF3 (platelet Factor 3) - A lipoprotein component of the platelet membrane; functions as a surface catalyst during blood coagulation.Pseudopod - A temporary protrusion of the cytoplasm of a cell.Refractile - Capable of refracting or changing the direction of light.Senescence - The process or condition of growing old.Serotonin - A constituent of blood platelets and other cells and organs; induces constriction of the blood vessels.Specific Granules - Granules found in cells of the more mature stages of the granulocytic series. They have distinct staining reactions which differ with each type of granulocyte.T-cell - Thymus derived lymphocyte which mediates cellular immunity.Thrombocyte (Platelet) - A circular or oval disk found in the blood; concerned with hemostasis.Thymus - A ductless gland-like body situated in the anterior mediastinal cavity; reaches its maximum development during the early years of childhood.Vacuole - Any small space or cavity formed in the cytotoplasm of a cell.

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During phagocytosis the neutrophilic granules release digestive enzymes into the vacuole to kill or destroy the phagocytized particle.View Page
Primary Function of Neutrophils

The primary function of neutrophils is phagocytosis, the ingestion and destruction of microorganisms or other foreign particles. For this reason, neutrophils are classified as phagocytes.

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Phagocytosis in a Neutrophil

When a neutrophil is faced with a microorganism or foreign particle, phagocytosis begins. The neutrophil extends pseudopods around the foreign material and engulfs it. Digestive enzymes present in the neutrophilic granules are released into the vacuole containing the foreign particle, and the particle is destroyed. In most cases a mild infection enhances the function of neutrophils while a severe infection impairs their function.

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The Process of Phagocytosis

Neutrophils have a relatively short life span.They are produced in the bone marrow, and when they reach the band or segmented stages are released into the peripheral blood.They remain there for approximately ten hours before randomly entering body tissues.Neutrophils in the blood stream can be divided into circulating granulocyte pool(CGP) and marginating granulocytic pool (MGP).The white blood cell count reflects the cells in the circulating pool.The cells in the marginating pool move quickly into the circulating pool when needed.During an infection the neutrophil concentration of the peripheral blood can increase almost immediately due to the shift of these cells from the marginating pool and release from the bone marrow storage pool, if needed.Neutrophils then migrate to areas of tissue damage or infection.Neutrophils do not reenter the blood stream from the tissues, thus end their life in the tissues either as a result of phagocytosis or senescence.

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Life Span and function of Eosinophils

Eosinophils have a circulating half-life of approximately 18 hours and a tissue life span of at least 6 days.They are capable of locomotion and phagocytosis and can enter inflammatory sites, but do so less readily than neutrophils.In tissues the primary location for eosinophils is in the epithelial barriers to the outside world such as, lungs, skin and GI tract.They are capable of returning to the circulating blood and bone marrow after they enter the tissues.

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Basophils' primary role involves:View Page

Variations in White Cell Morphology - Granulocytes
Hypersegmentation

A normal mature neutrophil is 9-13 microns in diameter and contains 3-5 lobes or segments.When the number of segments is increased to six or more the cell is hypersegmented. Some hypersegmented cells will be larger than in 15 microns. Hypersegmentation is seen most frequently in neutrophils but can also occur in eosinophils and basophils. The nuclear segments are composed of deoxyribonucleic acid (DNA). A defect in the production of DNA causes the maturation process to be slower than normal which in turn causes the nucleus to hypersegment. The cytoplasm will be normal in appearance and function, indicating that these cells are capable of phagocytosis.These cells are considered pathological

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Pelger-Huet Anomaly Does Not Affect Phagocytosis.

The main function of neutrophils is phagocytosis. This function is not affected in either the acquired or the inherited anomaly. Since inherited Pelger Huet Anomaly is associated with functionally normal neutrophils, they are considered a nonpathological variant.

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White Cell and Platelet Disorders: Peripheral Blood Clues to Nonneoplastic Conditions
Toxic granulation noted in the neutrophils' cytoplasm reflects an increase in activity of the: (more than one answer may be correct)View Page