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Medical Dictionary


immunity (i-mu′ni-te)
1. The status or quality of being immune (1). 2. Protection against infectious disease. SYN: insusceptibility. [L. immunitas (see immune)] acquired i. resistance resulting from previous exposure of the individual in question to an infectious agent or antigen; it may be active and specific, as a result of naturally acquired (apparent or inapparent) infection or intentional vaccination (artificial active i.); or it may be passive, being acquired from transfer of antibodies from another person or from an animal, either naturally, as from mother to fetus, or by intentional inoculation (artificial passive i.), and, with respect to the particular antibodies transferred, it is specific. Passive, cell-mediated i. produced by the transfer of living lymphoid cells from an immune (allergic or sensitive) animal to a normal one is sometimes referred to as adoptive i.. active i. acquired i.. adoptive i. acquired i.. antiviral i. i. resulting from virus infection, either naturally acquired or produced by intentional vaccination; compared to some bacterial immunities, it is of relatively long duration, but this may be the result of infection-i. rather than being peculiar to virus infection per se, since it occurs also in bacterial i. after infections such as typhoid fever. artificial active i. acquired i.. artificial passive i. acquired i.. bacteriophage i. the state induced in a bacterium by lysogenization, the lysogenic bacterium being insusceptible to further lysogenization or to a lytic cycle by a superinfecting bacteriophage, in contradistinction to bacteriophage resistance. cell-mediated i. (CMI) , cellular i. immune responses that are initiated by an antigen-presenting cell interacting with and mediated by T lymphocytes ( e.g., graft rejection, delayed-type hypersensitivity). SYN: delayed hypersensitivity (1) . concomitant i. SYN: infection i.. general i. i. associated with widely diffused mechanisms that tend to protect the body as a whole, as compared with local i.. group i. SYN: herd i.. herd i. the resistance to invasion and spread of an infectious agent in a group or community, based on the resistance to infection of a high proportion of individual members of the group; resistance is a product of the number susceptible and the probability that susceptibles will come into contact with an infected person. SYN: group i.. humoral i. i. associated with circulating antibodies, in contradistinction to cellular i.. infection i. the paradoxical immune status in which resistance to reinfection coincides with the persistence of the original infection. SYN: concomitant i.. innate i. resistance manifested by a species (or by races, families, and individuals in a species) that has not been immunized (sensitized, allergized) by previous infection or vaccination; much of it results from body mechanisms that are poorly understood, but are different from those responsible for the altered reactivity associated with the specific nature of acquired i.; in general, innate i. is nonspecific and is not stimulated by specific antigens. SEE ALSO: self. SYN: natural i., nonspecific i.. local i. a natural or acquired i. to certain infectious agents, as manifested by an organ or a tissue, as a whole or in part. maternal i. i. acquired by a fetus because of the presence of maternal IgG that passes through the placenta. natural i., nonspecific i. SYN: innate i.. passive i. acquired i.. relative i. a modified, not completely effective resistance that results when there is a sort of “fluctuating equilibrium” between the defense mechanisms of the host and the infective agent. specific i. the immune status in which there is an altered reactivity directed solely against the antigenic determinants (infectious agent or other) that stimulated it. See acquired i.. specific active i. acquired i.. specific passive i. acquired i.. stress i. insusceptibility or resistance to the effects of emotional strain.

immunization (im-mu′ni-za′shun)
Protection of susceptible individuals from communicable diseases by administration of a living modified agent ( e.g., yellow fever vaccine), a suspension of killed organisms ( e.g., pertussis vaccine), or an inactivated toxin ( e.g., tetanus). SEE ALSO: vaccination, allergization. active i. the production of active immunity. passive i. the production of passive immunity.

immunize (im′u-niz)
1. To render immune. 2. To administer immunization.

Immune, immunity. [L. immunis, immune]

immunoadjuvant (im′u-no-ad′joo-vant)
See adjuvant (2) .

immunoagglutination (im′u-no-a-gloo-ti-na′shun)
Specific agglutination effected by antibody.

immunoassay (im′u-no-as′a, im-u′no)
Detection and assay of substances by serological (immunological) methods; in most applications the substance in question serves as antigen, both in antibody production and in measurement of antibody by the test substance. SEE ALSO: enzyme-linked immunosorbent assay, radioimmunoassay, radioimmunoelectrophoresis, immunologic pregnancy test. SYN: immunochemical assay. double antibody i. SYN: double antibody precipitation. enzyme i. any of several i. methods that use an enzyme covalently linked to an antigen or antibody as a label; the most common types are enzyme-linked immunosorbent assay (ELISA) and enzyme-multiplied i. technique (EMIT). SEE ALSO: enzyme-linked immunosorbent assay, enzyme-multiplied i. technique. enzyme-multiplied i. technique (EMIT) a type of i. in which the ligand is labeled with an enzyme, and the enzyme-ligand-antibody complex is enzymatically inactive, allowing quantitation of unlabeled ligand. SEE ALSO: competitive binding assay, enzyme-linked immunosorbent assay. solid phase i. i. in which the antigen or serum is bound to a solid surface, such as a microplate wall or the sides of a tube, the other reactants being free in solution. thin-layer i. a method for detection of antigen-antibody reactions, applicable to detection of either antigen or antibody, based on the fact that either reactant, when added to a polystyrene surface (such as a well in a polystyrene plate) is adsorbed as a thin layer and acts as an immunosorbent capable of binding with the second reactant.

immunobiology (im′u-no-bi-ol-o-ije, im-oo′no)
The study of the immune factors that affect the growth, development, and health of biological organisms.

immunoblast (im′u-no-blast)
An antigenically stimulated lymphocyte; a large cell with well-defined basophilic cytoplasm, a large nucleus with prominent nuclear membrane, distinct nucleoli, and clumped chromatin. SEE ALSO: lymphoblast, lymphocyte transformation. [immuno- + G. blastos, germ]

immunoblot, immunoblotting (i′mu-no-blot′)
Process by which antigens can be separated by electrophoresis and allowed to adhere onto nitrocellulose sheets where they bind nonspecifically and then are subsequently identified by staining with appropriately labeled antibodies. SEE ALSO: Western blot analysis.

See immunoblot.

immunochemistry (im′u-no-kem′is-tre)
The field of chemistry concerned with chemical aspects of immunologic phenomena, e.g., chemical reactions related to antigen stimulation of tissues, chemical studies of antigens and antibody.

immunocompetence (im′u-no-kom′pe-tens)
The ability to produce a normal immune response.

immunocompetent (im′u-no-kom′pe-tent)
Possessing the ability to mount a normal immune response.

Complexes of antibody and antigen. See immune complex.

immunocompromised (im′u-no-kom′pro-mizd)
Denoting an individual whose immunologic mechanism is deficient either because of an immunodeficiency disorder or because it has been rendered so by immunosuppressive agents.

immunoconglutinin (im′u-no-kon-gloo′ti-nin)
An autoantibody-like immunoglobulin (IgM) formed in animals (or man) against their own complement following injection of complement-containing complexes or sensitized bacteria.

immunocyte (im′u-no-sit, im-oo′no)
An immunologically competent leukocyte capable, actively or potentially, of producing antibodies or reacting in cell-mediated immunity reactions. SEE ALSO: I cell. [immuno- + G. kytos, cell]

immunocytoadherence (im′u-no-si′to-ad-her′ens)
A method for determining cell surface properties, in which immunoglobulin or receptors on the surface of one cell population cause cells with corresponding molecular configurations on their surface to adhere in rosettes around the cells.

immunocytochemistry (im′u-no-si-to-kem′is-tre)
The study of cell constituents by immunologic methods, such as the use of fluorescent antibodies or immunoperoxidase staining..

immunodeficiency (im′u-no-de-fish′en-se, im-u′)
A condition resulting from a defective immune mechanism; may be primary (due to a defect in the immune mechanism itself) or secondary (dependent upon another disease process), specific (due to a defect in either the B-lymphocyte or the T-lymphocyte system, or both) or nonspecific (due to a defect in one or another component of the nonspecific immune mechanism: the complement, properdin, or phagocytic system). SYN: immune deficiency, immunity deficiency, immunologic deficiency. cellular i. with abnormal immunoglobulin synthesis an ill-defined group of sporadic disorders of unknown cause, occurring in both males and females and associated with recurrent bacterial, fungal, protozoal, and viral infections; there is thymic hypoplasia with depressed cellular (T-lymphocyte) immunity combined with defective humoral (B-lymphocyte) immunity, although immunoglobulin levels may be normal. SYN: Nezelof syndrome. combined i. i. of both the B-lymphocytes and T-lymphocytes. common variable i. i. of unknown cause, and usually unclassifiable; usual onset after age 15 years but may occur at any age in either sex; the total quantity of immunoglobulin is commonly less than 300 mg/dL; the number of B lymphocytes is often within normal limits but there is a lack of plasma cells in lymphoid tissue; cellular (T-lymphocyte) immunity is usually intact; there is an increased susceptibility to pyogenic infection and often autoimmune disease. SYN: acquired agammaglobulinemia, acquired hypogammaglobulinemia. phagocytic dysfunction i. suppression in number or function of phagocytic cells such as in chronic granulomatous disease. SYN: phagocytic dysfunction disorders i.. phagocytic dysfunction disorders i. SYN: phagocytic dysfunction i.. secondary i. i. in which there is no evident defect in the lymphoid tissues, but rather hypercatabolism or loss of immunoglobulins such as occurs in familial idiopathic hypercatabolic hypoproteinemia or in defects associated with the nephrotic syndrome. SYN: secondary agammaglobulinemia, secondary antibody deficiency, secondary hypogammaglobulinemia. severe combined i. (SCID) [MIM*202500,MIM*300400, and MIM*312863] an i. in which there is absence of both humoral and cellular immunity with lymphopenia (of both B-type and T-type lymphocytes); characterized by thymus atrophy, lack of delayed hypersensitivity, and marked susceptibility to infections by bacteria, viruses, fungi, protozoa, and live vaccines; although bone marrow transplants have been effective, death may occur in the first year of life. Both autosomal recessive and X-linked forms occur; about one-half of those with autosomal recessive SCID have adenosine deaminase deficiency. The X-linked form is caused by mutation in the interleukin-2 receptor gamma gene (IL2RG) on Xq. SYN: Swiss type agammaglobulinemia. i. with elevated IgM i. with reduced IgG- and IgA-bearing cells; there is recurrent pyogenic infection; X-linked in some families. i. with hypoparathyroidism SYN: DiGeorge syndrome.

immunodeficient (im′u-no-de-fish′ent)
Lacking in some essential function of the immune system.

immunodepressant (im′u-no-de-pres′ant)
SYN: immunosuppressant.

immunodepressor (im′u-no-de-pres′or, -or)
SYN: immunosuppressant.

immunodiagnosis (im′u-no-di-ag-no′sis)
The process of determining specified immunologic characteristics of individuals or of cells, serum, or other biologic specimens.

immunodiffusion (im′u-no-di-fu′zhun,, im-u′no-)
A technique to study antigen-antibody reactions by observing precipitates formed by antigen-antibody complexes, which are formed by combination of specific antigen and antibodies which have diffused in a gel in which they have been separately placed. double i. gel diffusion precipitin tests in two dimensions, under test. radial i. (RID) gel diffusion precipitin tests in one dimension, under test. single i. gel diffusion precipitin tests in one dimension, under test, gel diffusion precipitin tests in two dimensions, under test.

immunoelectrophoresis (im′u-no-e-lek′tro-fo-re′sis)
A kind of precipitin test in which the components of one group of immunological reactants (usually a mixture of antigens) are first separated on the basis of electrophoretic mobility in agar or other medium, the separated components then being identified, by means of the technique of double diffusion, on the basis of precipitates formed by reaction with components of the other group of reactants (antibodies). crossed i. SYN: two-dimensional i.. rocket i. a quantitative method for serum proteins that involves electrophoresis of antigen into a gel containing antibody; the technique is restricted to detection of antigens that move to the positive pole on electrophoresis. See electroimmunodiffusion. two-dimensional i. a combination of conventional electrophoretic separation and electroimmunodiffusion; electrophoresis is first carried out, then the electrophoretic strip is placed on a second slide and an antibody-containing agarose solution is allowed to solidify adjacent to it; electrophoresis is then performed at right angles to the original separation. SYN: crossed i..

immunoenhancement (im′u-no-en-hans′ment)
Increasing the immune response; aside from antibody, nonspecific substances may also act to enhance immune response. SYN: immunologic enhancement.

immunoenhancer (im′u-no-en-hans′er)
Any specific or nonspecific substance that increases the degree of the immune response.

immunoferritin (im′u-no-fer′i-tin)
Antibody-ferritin conjugate used to identify specific antigen by electron microscopy.

immunofluorescence (im′u-no-flor-es′ens, i-mu′no-)
An immunohistochemical technique using labeling of antibodies by a fluorescent dye to identify antigenic material specific for the labeled antibody; the specific binding of antibody can be determined microscopically through the production of a characteristic visible light by the application of ultraviolet rays to the preparation. SEE ALSO: fluorescent antibody technique. direct i. fluorescence microscopy of tissue from lesions after application of labeled antibodies. SEE ALSO: fluorescent antibody technique. indirect i. fluorescence microscopy of normal tissue after application of the patient's serum, to detect antibodies to normal tissue components (autoantibodies). SEE ALSO: fluorescent antibody technique.

immunogen (i-mu′no-jen)
SYN: antigen.

immunogenetics (im′u-no-je-net′iks, im-u′no-)
The study of the genetics of transplantation and tissue rejection, histochemical loci, immunologic response, immunoglobulin structure, and immunosuppression.

immunogenic (im′u-no-jen′ik)
SYN: antigenic.

immunogenicity (im′u-no-je-nis′i-te)
SYN: antigenicity.

immunoglobulin (Ig) (im′u-no-glob′u-lin)
One of a class of structurally related proteins, each consisting of two pairs of polypeptide chains, one pair of light (L) [low molecular weight] chains (κ or λ), and one pair of heavy (H) chains (γ, α, μ, δ, and ε), usually all four linked together by disulfide bonds. On the basis of the structural and antigenic properties of the H chains, Ig's are classified (in order of relative amounts present in normal human serum) as IgG (7S in size, 80%), IgA (10–15%), IgM (19S, a pentamer of the basic unit, 5–10%), IgD (less than 0.1%), and IgE (less than 0.01%). All of these classes are homogeneous and susceptible to amino acid sequence analysis. Each class of H chain can associate with either κ or λ L chains. Subclasses of Ig's, based on differences in the H chains, are referred to as IgG1, etc. When split by papain, IgG yields three pieces: the Fc piece, consisting of the C-terminal portion of the H chains, with no antibody activity but capable of fixing complement, and crystallizable; and two identical Fab pieces, carrying the antigen-binding sites and each consisting of an L chain bound to the remainder of an H chain. Antibodies are Ig's, and all Ig's probably function as antibodies. However, Ig refers not only to the usual antibodies, but also to a great number of pathological proteins classified as myeloma proteins, which appear in multiple myeloma along with Bence Jones proteins, myeloma globulins, and Ig fragments. From the amino acid sequences of Bence Jones proteins, it is known that all L chains are divided into a region of variable sequence (VL) and one of constant sequence (CL), each comprising about half the length of the L chain. The constant regions of all human L chains of the same type (κ or λ) are identical except for a single amino acid substitution, under genetic controls. H chains are similarly divided, although the VH region, while similar in length to the VL region, is only one-third or one-fourth the length of the CH region. Binding sites are a combination of VL and VH protein regions. The large number of possible combinations of L and H chains make up the “libraries” of antibodies of each individual. anti-D i. SYN: RHo(D) immune globulin. chickenpox i. SYN: chickenpox immune globulin (human). i. domains structural units of i. heavy or light chains that are composed of approximately 110 amino acids. Light chains of an i. are composed of one constant domain and one variable domain. Heavy chains are composed of either three or four constant domains and one variable domain. i. G subclass deficiency a rare inherited disorder in which there are reduced levels of one or more IgG subclasses resulting from defective heavy chain genes or an abnormality in the regulation of i. isotype switching. human normal i. SYN: human gamma globulin. measles i. SYN: measles immune globulin (human). monoclonal i. a homogeneous i. resulting from the proliferation of a single clone of plasma cells and which, during electrophoresis of serum, appears as a narrow band or “spike”; it is characterized by heavy chains of a single class and subclass, and light chains of a single type. SYN: M protein (2) , monoclonal protein, paraprotein (2) . pertussis i. SYN: pertussis immune globulin. poliomyelitis i. SYN: poliomyelitis immune globulin (human). rabies i. SYN: rabies immune globulin (human). Rho(D) i. SYN: RHo(D) immune globulin. secretory i. usually IgA but may be IgM linked to a secretory component and found in mucous secretions. secretory i. A a subclass of IgA that is found primarily in secretions such as tears and colostrum. This form of IgA is protected from proteolytic degradation by the presence of a secretory component. selective i. A deficiency an inherited disorder in which there is a markedly reduced or absent IgA, resulting in immature IgA-bearing B cells. tetanus i. SYN: tetanus immune globulin. thyroid-stimulating immunoglobulins (TSI) in Graves disease, the antibodies to TSH receptors in the thyroid gland. These antibodies are produced by B-lymphocytes and stimulate the receptors, causing hyperthyroidism. Formerly known as LATS (long-acting thyroid stimulator).

immunohematology (im′u-no-he-ma-tol′o-je, im-u′no-)
That division of hematology concerned with immune, or antigen-antibody reactions and with related changes in the blood.

immunohistochemistry (im′u-no-his′to-kem′is-tre)
Demonstration of specific antigens in tissues by the use of markers that are either fluorescent dyes or enzymes such as horseradish peroxidase.

immunolocalization (im′u-no-lo′cal-i-za-shun)
Refers to use of immunologic techniques, including specific antibody, to identify the location of molecules or structures within cells or tissues.

immunologist (im-u-nol′o-jist)
A specialist in the science of immunology.

immunology (im′u-nol′o-je)
1. The science concerned with the various phenomena of immunity, induced sensitivity, and allergy. 2. Study of the structure and function of the immune system. [immuno- + G. logos, study]

immunomodulatory (im′u-no-mod′u-la-to-re)
1. Capable of modifying or regulating one or more immune functions. 2. An immunological adjustment, regulation, or potentiation.

immunopathology (im′u-no-pa-thol′o-je, i-moo′no-)
The study of diseases or conditions resulting from immune reactions.

immunophilins (im′u-no-fil′inz)
High-affinity receptor proteins in the cytoplasm that combine with immunosuppressant drugs leading to rotamase inhibition and, in T cells, thus to interruption of cell activation. [immune + G. philos, fond, + in]

immunopotentiation (im′u-no-po-ten-she-a′shun)
Enhancement of the immune response by increasing its rate or prolonging its duration.

immunopotentiator (im′u-no-po-ten′she-a-tor)
Any of a wide variety of specific or nonspecific substances which on inoculation enhances or augments an immune response.

immunoprecipitation (im′u-no-pre-sip-i-ta′shun)
The phenomenon of aggregation of sensitized antigen upon addition of specific antibody (precipitin) to antigen in solution. SYN: immune precipitation.

immunoreaction (im′u-no-re-ak′shun)
An immunologic reaction, especially in vitro between antigen and antibody.

immunoreactive (im′u-no-re-ak′tiv)
Denoting or exhibiting immunoreaction.

immunoselection (im′u-no-se-lek′shun)
1. Selective death or survival of fetuses of different genotypes depending on immunologic incompatibility with the mother. 2. The survival of certain cells depending on their surface antigenicity.

immunosorbent (im′u-no-sor′bent)
An antibody (or antigen) used to remove specific antigen (or antibody) from solution or suspension; commonly used with reference to antibody bound to a particulate substance such as a dextran polymer used to remove soluble antigen ( e.g., insulin) from solution.

immunosuppressant (im′u-no-su-pres′ant)
An agent that induces immunosuppression ( e.g., cyclosporine, corticosteroids). SYN: immunodepressant, immunodepressor, immunosuppressive (2) .

immunosuppression (im′u-no-su-presh′un)
Prevention or interference with the development of immunologic response; may reflect natural immunologic unresponsiveness (tolerance), may be artificially induced by chemical, biological, or physical agents, or may be caused by disease.

immunosuppressive (im′u-no-su-pres′iv)
1. Denoting or inducing immunosuppression. 2. SYN: immunosuppressant.

immunosurveillance (im′u-no-ser-va′lance)
Theory that holds that the immune system eliminates aberrant or tumor cells that arise spontaneously.

immunosympathectomy (im′u-no-sim′pa-thek′to-me)
Inhibition of development of sympathetic ganglia induced in newborn animals by injection of antiserum specific for the protein which selectively enhances growth of sympathetic neurons.

immunotherapy (im′u-no-thar′a-pe)
Originally, therapeutic administration of serum or immune globulin containing preformed antibodies produced by another individual; currently, i. includes nonspecific systemic stimulation, adjuvants, active specific i., and adoptive i.. New forms of i. include the use of monoclonal antibodies. SYN: biologic i..This method has been widely adopted in oncology, particularly in cases that fail to respond to other treatment. I. seeks to boost immune system function, as with the administration of interferons and interleukin-2, or to attack cancerous cells directly, as with the injection of monoclonal antibodies. Various immunotherapeutic techniques have also been used in the treatment of AIDS. In addition, a number of alternative medical practices are claimed to enhance immune function, and various over-the-counter substances have gained popularity for this supposed property. adoptive i. passive transfer of immunity from an immune donor through inoculation of sensitized lymphocytes, or antibodies in serum or gamma globulin. Vaccination with plasmid DNA is currently under investigation. biologic i. SYN: i..

immunotolerance (im′u-no-tol′er-ans)
SYN: immunologic tolerance.

immunotransfusion (im′u-no-trans-fu′zhun, i-moo′no-)
An indirect transfusion in which the donor is first immunized by means of injections of an antigen prepared from microorganisms isolated from the recipient; later, the donor's blood is collected, defibrinated, and then administered to the patient; the latter is then presumably passively immunized by means of antibody formed in the donor, e.g., antibody that reacts with the microorganisms in the patient.

Abbreviation for inosine 5′-monophosphate.

1. (im′pakt)The forcible striking of one body against another. 2. (im-pakt′)To press two bodies, parts, or fragments closely together so that the two parts move as a single unit. [L. impingo, pp. -pactus, to strike at (in + pango), fasten, drive in]

impacted (im-pak′ted)
Wedged or pressed closely so as to move as a single unit.

impaction (im-pak′shun)
The process or condition of being impacted. dental i. confinement of a tooth in the alveolus and prevention of its eruption into normal position. SEE ALSO: impacted tooth. fecal i. an immovable collection of compressed or hardened feces in the colon or rectum. food i. the forcible wedging of food between adjacent teeth during mastication, producing gingival recession and pocket formation. mucus i. filling of the proximal bronchi, and also the bronchioles, with mucus.


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