variable region

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im·mu·no·glob·u·lin (Ig),

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 by disulfide bonds. On the basis of the structural and antigenic properties of the H chains, immunoglobulins 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 immunoglobulin, 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 immunoglobulins, and all immunoglobulins probably function as antibodies. However, immunoglobulin refers not only to the usual antibodies, but also to a great number of pathologic proteins classified as myeloma proteins, which appear in multiple myeloma along with Bence Jones proteins, myeloma globulins, and immunoglobulin 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, although 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.
Farlex Partner Medical Dictionary © Farlex 2012

variable region

The portion of the amino terminal of an immunoglobulin's heavy and light chains having a variable amino acid sequence.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

variable region

The part of an antibody at the tip of each arm (N-terminal region) that varies considerably in its amino acid sequence from one antibody to another. The remaining parts of the structure of antibodies are fixed and almost identical. This region is coded for by the V gene.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005

variable (V) region

an area of an IMMUNOGLOBIN molecule that is specific to that particular molecule. Compare CONSTANT REGION.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005
References in periodicals archive ?
Only hyper variable region of 18-S rDNA gene was selected to target for amplification with common pair of oligos not only to diagnose dermatophytosis but also to differentiate between two common genera of dermatophytes based upon amplicon sizes, hence reducing the assay labour and complexity.
The variable regions make the plasmids different in size and genomic structure.
CD38 expression and immunoglobulin variable region mutations are independent prognostic variables in chronic lymphocytic leukemia, but CD38 expression may vary during the course of the disease.
The selection criteria established were as follows: the peptide had an [IC.sub.50] below 500 nM [43] and was not present in the variable region of a control IgM anti-ganglioside antibody, which is not immunogenic in the syngeneic model.
When we analyzed the sequence of our aptamer (M7-14) against one of the predominant aptamers (C3) selected by this group, we observed that the variable region of C3 and part of M7-14's variable region were 64% identical (Figure 4(a)).
The integrons variable region analysis identified the172 isolates and 8 kinds of sequence were found by PCR and sequencing them.
Monitoring M-proteins in patients with multiple myeloma using heavy-chain variable region clonotypic peptides and LC-MS/MS.
Different degrees of genetic polymorphisms were observed in the amplified variable regions of L.
I munoglobulin heavy chain variable region gene usage and mutational status of the leukemic B cells in Iranian patients with chronic lymphocytic leukemia.
A related G&D invention is described in WO2010022952A1, where the variable region switches from transparent to coloured.
This variable region, we now realize, is the part of the antibody that binds antigen, and the source of this variableness is what Lennox and Cohn were speculating about in their review.

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