fixation /fix·a·tion/ (fik-sa´shun)
complement fixation,
complement [kom´plĕ-ment]
1. the process of holding, suturing, or fastening in a fixed position.
2. the condition of being held in a fixed position.
3. in psychiatry: (a) arrest of development at a particular stage, or (b) a close suffocating attachment to another person, especially a childhood figure, such as a parent.
4. the use of a fixative to preserve histological or cytological specimens.
5. in chemistry, the process whereby a substance is removed from the gaseous or solution phase and localized.
6. in ophthalmology, direction of the gaze so that the visual image of the object falls on the fovea centralis.
7. in film processing, removal of all undeveloped salts of the film emulsion, leaving only the developed silver to form a permanent image.
complement fixation , fixation of complement addition of another serum containing an antibody and the corresponding antigen to a hemolytic serum, making the complement incapable of producing hemolysis.
| complement fixation n. The binding of active complement to a specific antigen-antibody pair used in diagnostic tests, such as the Wasserman test, to detect the presence of a specific antigen or antibody. |
complement fixation,
an immunologic reaction in which an antigen combines with an antibody and its complement, causing the complement factor to become inactive or fixed. The complement-fixation reaction can be tested in the laboratory by exposing the patient's serum to antigen, complement, and specially sensitized red blood cells. Complement-fixation tests can be used to detect antibodies for infectious diseases, especially syphilis and viral illnesses. They are rarely used in clinical practice today. See also anticomplement, complement, immune system, immunity, Wassermann blood test.
complement [kom´plĕ-ment]
a term originally used to refer to the heat-labile factor in serum that causes immune cytolysis (lysis of antibody-coated cells). It is now used to refer to the entire functionally related system comprising at least 20 distinct serum proteins, their cellular receptors, and related regulatory proteins; this system is the effector not only of immune cytolysis but also of other biologic functions including anaphylaxis, phagocytosis, opsonization, and hemolysis.
Complement activation occurs by two different sequences, the classical pathway and the alternative pathway. All of the “components of complement,” designated C1 through C9 (C1 being composed of three distinct proteins, C1q, C1r, and C1s), participate in the classical pathway; the alternative pathway lacks components C1, C2, and C4 but adds factor b, factor d, and properdin. Regulatory proteins include factor h, factor i, clusterin, C3 nephritic factor, decay accelerating factor, homologous restriction factor, C1 inhibitor, C4 binding protein, membrane cofactor protein, protectin, and vitronectin.
The classical pathway is primarily activated by the binding of C1 to antigen-antibody complexes containing the immunoglobulins IgM or IgG. The alternative pathway can be activated by IgA immune complexes and also by nonimmunologic materials including bacterial endotoxins, microbial polysaccharides, and cell walls. Activation of the classical pathway triggers an enzymatic cascade involving C1, C4, C2, and C3; activation of the alternative pathway triggers a cascade involving C3 and factors B and D and properdin. Both pathways result in cleavage of C5 and formation of the membrane attack complex, which in its final state creates a pore in the cell wall and causes cell lysis. Complement activation also results in the formation of many biologically active complement fragments that act as anaphylatoxins, opsonins, or chemotactic factors. Fragments resulting from proteolytic cleavage of complement proteins are designated with lower-case-letter suffixes, e.g., C3a.
Complement activation occurs by two different sequences, the classical pathway and the alternative pathway. All of the “components of complement,” designated C1 through C9 (C1 being composed of three distinct proteins, C1q, C1r, and C1s), participate in the classical pathway; the alternative pathway lacks components C1, C2, and C4 but adds factor b, factor d, and properdin. Regulatory proteins include factor h, factor i, clusterin, C3 nephritic factor, decay accelerating factor, homologous restriction factor, C1 inhibitor, C4 binding protein, membrane cofactor protein, protectin, and vitronectin.
The classical pathway is primarily activated by the binding of C1 to antigen-antibody complexes containing the immunoglobulins IgM or IgG. The alternative pathway can be activated by IgA immune complexes and also by nonimmunologic materials including bacterial endotoxins, microbial polysaccharides, and cell walls. Activation of the classical pathway triggers an enzymatic cascade involving C1, C4, C2, and C3; activation of the alternative pathway triggers a cascade involving C3 and factors B and D and properdin. Both pathways result in cleavage of C5 and formation of the membrane attack complex, which in its final state creates a pore in the cell wall and causes cell lysis. Complement activation also results in the formation of many biologically active complement fragments that act as anaphylatoxins, opsonins, or chemotactic factors. Fragments resulting from proteolytic cleavage of complement proteins are designated with lower-case-letter suffixes, e.g., C3a.
Complement activation. Activation of the classical and alternative pathways leads to a common terminal pathway from C5 to C9. These complement components form the final membrane attack complex (MAC). Other intermediate complexes and fragments are also biologically active: opsonins facilitate phagocytosis, anaphylatoxins act on mast cells and mediate a release of histamine which acts on blood vessels, and chemotactic fragments and intermediate complexes attract leukocytes to the site of inflammation. Redrawn from Damjanov, 2000.
complement fixation the combining of complement with the antigen-antibody complex, rendering the complement inactive, or fixed. Its presence or absence as free, active complement can be shown by adding sensitized blood cells to the mixture. If free complement is present, hemolysis occurs; if not, no hemolysis is observed. This reaction is the basis of many serologic tests for infection, including the wassermann test for syphilis, and reactions for gonococcus infection, glanders, typhoid fever, tuberculosis, and amebiasis. Called also Bordet-Gengou phenomenon. See also immunity.
complement fixation tests tests that use antigen-antibody reaction and result in hemolysis to determine the presence of various organisms in the blood; see also complement fixation.
fixation [fik-sa´shun]
1. the act or operation of holding, suturing, or fastening in a fixed position.
2. the condition of being held in a fixed position.
3. in psychiatry, a term with two related but distinct meanings: (a) arrest of development at a particular stage (if this is temporary it is a normal reaction to difficulties, but if continued it is a cause of emotional problems); and (b) a close and suffocating attachment to some person, especially a childhood figure such as a parent.
4. in microscopy, the treatment of material so that its structure can be examined in greater detail with minimal alteration of the normal state, and also to provide information concerning the chemical properties (as of cell constituents) by interpretation of fixation reactions.
5. in chemistry, the process whereby a substance is removed from the gaseous or solution phase and localized, as in carbon dioxide or nitrogen fixation.
6. in ophthalmology, direction of the gaze so that the visual image of the object falls on the fovea centralis.
7. in film processing, the chemical removal of all unexposed and undeveloped silver compounds of the film emulsion, as on x-ray films.
complement fixation see complement fixation.
intermaxillary fixation (IMF) a technique used to stabilize a fractured jaw; the teeth are wired or banded together. Extreme caution must be exercised to insure that oral secretions and vomitus are not aspirated as the patient is unable to expectorate any fluids. Antiemetics are often administered to prevent vomiting. Wire cutters should be kept with the patient at all times.
Teeth wired in intermaxillary fixation. From Ignatavicius et al., 1995.
complement fixation,
n an immune reaction in which an antigen-antibody complex inactivates or fixes the complement of the antibody. Complement fixation tests are used to determine antibodies for infectious diseases, such as syphilis and certain viral infections.
)
Complement fixation.
complement (kom´pl
ment),n one of 11 complex, enzymatic serum proteins. In an antigen-antibody reaction, complement causes lysis. Complement is also involved in anaphylaxis and phagocytosis.
complement fixation,
n an immunologic reaction in which an antigen combines with an antibody and its complement, causing the complement factor to become inactive, or “fixed.”
complement-fixation test (C-F test),
n a serologic test in which complement fixation is detected, indicating the presence of a particular antigen. The Wassermann test for syphilis is a C-F test, used to detect amebiasis, Rocky Mountain spotted fever, try-panosomiasis, and typhus.
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