MHC

MHC major histocompatibility complex.

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MHC

abbr.

major histocompatibility complex

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MHC,

abbreviation for major histocompatibility complex. See HLA complex.

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complex [kom´pleks]

1. the sum, combination, or collection of various things or related factors, like or unlike; e.g., a complex of symptoms (see syndrome).

2. a group of interrelated ideas, mainly unconscious, that have a common emotional tone and strongly influence a person's attitudes and behavior.

3. that portion of an electrocardiographic tracing which represents the systole of an atrium or ventricle.

AIDS-related complex (ARC) a complex of signs and symptoms occurring in HIV infection including fever, weight loss, prolonged diarrhea, minor opportunistic infections, lymphadenopathy, and changes in cells of the immune system.

antigen-antibody complex here the complex formed by the noncovalent binding of an antibody and antigen. Complexes of antibodies belonging to certain immunoglobulin classes may activate complement. Called also immune complex.

anti-inhibitor coagulant complex (AICC) a concentrated fraction from pooled human plasma, which includes various coagulation factors. It is administered intravenously as an antihemorrhagic in hemophilic patients with inhibitors to coagulation factor VIII.

atrial complex the P wave of the electrocardiogram, representing electrical activity of the atria. See also ventricular complex.

castration complex in psychoanalytic theory, unconscious thoughts and motives stemming from fear of loss of the genitals as punishment for forbidden sexual desires.

Electra complex libidinous fixation of a daughter toward her father. This term is rarely used, since oedipus complex is generally applied to both sexes.

factor IX complex a sterile, freeze-dried powder consisting of partially purified coagulation factor IX fraction, as well as concentrated factor II, VII, and X fractions, of venous plasma from healthy human donors. It is used in the prophylaxis and treatment of bleeding in patients with hemophilia B, replacement of factor VII in patients deficient in that factor, and treatment of anticoagulant-induced hemorrhage. Administered intravenously.

Ghon complex primary complex (def. 1).

Golgi complex golgi apparatus.

HLA complex the human major histocompatibility complex, which contains the hla antigens.

immune complex antigen-antibody complex.

inclusion complex one in which molecules of one type are enclosed within cavities in the crystalline lattice of another substance.

inferiority complex unconscious feelings of inadequacy, producing shyness or timidity or, as a compensation, exaggerated agressiveness and expression of superiority; based on Alfred Adler's concept that everyone is born with a feeling of inferiority stemming from real or imagined physical or psychological deficiency, with the manner in which the inferiority is handled determining behavior.

interpolated premature ventricular complex a premature ventricular complex that does not interfere with the conduction of the next sinus beat, i.e., it lacks the usual following compensatory pause.

major histocompatibility complex (MHC) the chromosomal region containing genes that control the histocompatibility antigens; in humans it controls the hla antigens.

membrane attack complex (MAC) C5b,6,7,8,9, the five-molecule complex that is the cytolytic agent of the complement system.

Oedipus complex see oedipus complex.

primary complex

1. the combination of a parenchymal pulmonary lesion (Ghon focus) and a corresponding lymph node focus, occurring in primary tuberculosis, usually in children. Similar lesions may also be associated with other mycobacterial infections and with fungal infections.

2. the primary cutaneous lesion at the site of infection in the skin, e.g., chancre in syphilis and tuberculous chancre.

QRS complex a group of waves seen on an electrocardiogram, representing ventricular depolarization. Called also QRS wave. It actually consists of three distinct waves created by the passage of the cardiac electrical impulse through the ventricles and occurs at the beginning of each ventricular contraction. In a normal surface electrocardiogram the R wave is the upward deflection; the first downward deflection represents a Q wave and the final downward deflection is the S wave. The Q and S waves may be extremely weak and sometimes are absent.

One abnormality of the QRS complex is increased voltage resulting from enlargement of heart muscle, which produces increased quantities of electric current. A low-voltage QRS complex may result from toxic conditions of the heart, most commonly from fluid in the pericardium. Pleural effusion and emphysema also can cause a decrease in the voltage of the QRS complex.

VATER complex an association of congenital anomalies consisting of vertebral defects, imperforate anus, tracheoesophageal fistula, and radial and renal dysplasia.

ventricular complex the Q, R, S, and T waves of the electrocardiogram, representing ventricular electrical activity. See also atrial complex.

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MHC

major histocompatibility complex.

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MHC

Major histocompatibility complex A small region of the genome that is highly conserved in vertebrate evolution, which encodes 3 classes of polymorphic molecules known as the immune recognition unit; the MHC is located on the short arm of chromosome 6 in humans; the products of the MHC gene complex are membrane-bound receptors for antigens and peptides which, when bound, are displayed to T cells; if the bound peptides are recognized by the T cells, an immune response against those peptidesis initiated