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chemotactic peptide 165 Chido (Ch) and Rodgers (Rg) antigens
These chemotactic factors are derived from both inflammatory
and noninflammatory cells including neutrophils, macrophages,
smooth muscle cells, fibroblasts, epithelial cells,
and endothelial cells. MCP-1 participates in the recruitment
of monocytes in various pathologic or physiologic conditions.
Neutrophil chemotaxis assays are performed using the
microchamber technique. Chemotactic assays are also useful
to reveal the presence of chemotaxis inhibitors in serum.
chemotactic peptide
A peptide that attracts cell migration, such as formylmethionyl-leucyl-phenylalanine.
chemotactic receptor
Cellular receptor for chemotactic factor. In bacteria, such
receptors are designated sensors and signalers and are
associated with various transport mechanisms. The cellular
receptors for chemotactic factors have not been isolated
and characterized. In leukocytes, the chemotactic receptor
appears to activate a serine proesterase enzyme, which sets in
motion the sequence of events related to cell locomotion. The
receptors appear specific for the chemotactic factors under
consideration, and apparently the same receptors mediate all
types of cellular responses inducible by a given chemotactic
factor. However, these responses can be dissociated from
each other, suggesting that binding to the putative receptor
initiates a series of parallel, interdependent, and coordinated
biochemical events leading to one or another type of
response. Using a synthetic peptide, N-formyl-methionylleucyl-phenylalanine,
about 2000 binding sites have been
demonstrated for each polymorphonuclear neutrophil (PMN)
leukocyte. The binding sites are specific, have a high affinity
for the ligand, and are saturable. Competition for the binding
sites is shown only by the parent or related compounds; the
potency of the latter varies. Positional isomers may inhibit
binding. Full occupancy of the receptors is not required for a
maximal response, and occupancy of only 10 to 20% of them
is sufficient. The presence of spare receptors may enhance
the sensitivity in the presence of small concentrations of
chemotactic factors and may contribute to the detection
of a gradient. There also remains the possibility that some
substances with chemotactic activity do not require specific
binding sites on cell membranes.
Chemotactic factor
f. Met - Leu - Phe
Chemotaxis.
PMN
Leukocytes
Micropore filter
chemotaxis
The process whereby chemical substances direct cell movement
and orientation. The orientation and movement of
cells in the direction of a concentration gradient constitute
positive chemotaxis, whereas movement away from the
concentration gradient is termed negative chemotaxis.
Substances that induce chemotaxis are referred to as
chemotaxins and are often small molecules, such as C5a,
formyl peptides, lymphokines, bacterial products, leukotriene
B 4, etc., that induce positive chemotaxis of polymorphonuclear
neutrophils, eosinophils, and monocytes.
These cells move into inflammatory agents by chemotaxis.
Chemotaxis is measured by using a dual-chamber device
called a Boyden chamber, in which phagocytic cells in culture
are separated from a chemotactic substance by a membrane.
The number of cells on the filter separating the cell
chamber from the chemotaxis chamber reflect the chemotactic
influence of the chemical substance for the cells.
chemotherapy
Treatment of neoplasia with chemical drugs that destroy
tumor cells that grow more rapidly than do normal cells or
have a metabolic disorder.
chickenpox (varicella)
Human herpesvirus type 3 (HHV-3) induced in acute
infection that usually occurs in children below 10 years of
age. There is anorexia, malaise, low fever, and a prodromal
rash following a 2-week incubation period. Erythematous
papules appear in crops and intensify for 3 to 4 days. They
are very pruritic. Complications include viral pneumonia,
secondary bacterial infection, thrombocytopenia, glomerulonephritis,
myocarditis, and other conditions. HHV-3
may become latent when chickenpox resolves. Its DNA may
become integrated into the dorsal route ganglion cells that
may be associated with the development of herpes zoster or
shingles later in life.
Phenotype
C4d Component
Present
Frequency (%)
Whites
Ch(a+), Rg(a+) C4dS, C4df 95
Ch(a–), Rg(a+) C4df 2
Ch(a+), Rg(a–) C4dS 3
Ch(a–), Rg(a–) None Very rare
Chido (Ch) and Rodgers (Rg) Antigens
Chido (Ch) and Rodgers (Rg) antigens
Epitopes of C4d fragments of human complement component
C4. They are not intrinsic to the erythrocyte
membrane. The Chido epitope is found on C4d from C4B,
whereas the Rodgers epitope is found on C4A derived from
C4d. The Rodgers epitope is Val–Asp–Leu–Leu, and the
Chido epitope is Ala–Asp–Leu–Arg. They are situated
at residue positions 1188 and 1191 in the C4d region of
the C4 α chain. Antibodies against Ch and Rg antigenic
determinants agglutinate saline suspensions of red blood
cells coated with C4d. Because C4 is found in human
serum, anti-Ch and anti-Rg are neutralized by sera of most
individuals having the relevant antigens. Ficin and papain
destroy these antigens.
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