Immunoglobulin subclasses

Table 4.8. Binding affinities of immunoglobulin subclasses from different species to immobilized Protein A, Protein G, Protein L, and thiophilic chromatography supports...

Willison, H.J., Veitch, J. Immunoglobulin subclass distribution and binding characteristics of anti-GQm antibodies in Miller Fisher syndrome. J Neuroimmunol 50 (1994) 159-165. 

Isotype Iso (Gr. equal) isotype usually refers to the immunoglobulin subclasses as... 

HAMMARSTROM, L. SMITH, C.I.E. (1987) Immunoglobulin subclass distribution of specific antibodies in allergic patients. Allergy, 42, 529-536. 

Although mAbs share high sequence similarity within an immunoglobulin subclass, they can have dramatically different physical and chemical stability properties unique to a specific mAb. Hence, individual formulation strategies are needed to address different types of physical and chemical instabilities observed for different mAbs formulated in various dosage forms [45]. Stabilization strategies... 

Kuwabara K, Shudo K, Hori Y (1996) Novel synthetic retinoic acid inhibits rat collagen arthritis and differentially affects serum immunoglobulin subclass levels. FEBS Lett 378 153-156... 

Fc function (portion of fully functional immunoglobulin molecule) prekailikrein activator, <35 lU/mL HBsAs antibody, >1 lU/g normal subclass distribution osmolality, <280 mosmol 4 to 7.4 pH. Ref. 221. 

H, Devey ME Immunoglobulin class and subclass distribution of dextran-reactive antibodies in human reactors and non-reactors to clinical dex-tran. Allergy 1982 37 481-489. 

It is present at serum levels between 0.5 and 3mgmH but higher concentrations are found in secretions. There are two subclasses of this immunoglobulin. 

Kett K, Baklien K, Bakken A, Krai JG, Fausa O, Brandtzaeg P Intestinal B-cell isotype response in relation to local bacterial load Evidence for immunoglobulin A subclass adaptation. Gastroenterology 1995 109 819-825. 

Protein A and protein G are bacterial proteins (constituents bacterial cell wall) that bind with high affinity to the Fc portion of various classes and subclasses of immunoglobulins from a variety of species. The use of protein A and protein G in immunohistochemistry is based on the same principle as that using secondary anti-IgG antibodies in indirect two-step approach. 

IgA has a short half-life in serum (6 days) and comprises about 12-20% of the total serum immunoglobulins. However, because of its presence in bodily fluids, it is the most abundant immunoglobulin present in the body. It comprises three constant domains, and neutrophils, monocytes and some other immune cells possess receptors for IgA (FcaR). Neither of the two IgA subclasses, IgAi and IgA2, can fix complement via the classical pathway. Instead, these antibodies neutralise antigens at mucosal surfaces, in the absence of complement fixation (which would be pro-inflammatory), and the neutralised antigens are cleared. 

IgG The major immunoglobulin in human serum. There are four subclasses of IgG IgGl, IgG2, IgG3 and IgG4, but this number varies in different species. All are able to cross the placenta, and the first three subclasses fix complement by the classical pathway. The molecular mass of human IgG is 150 kDa and the normal serum concentration in man is 16 mg ml-1. 

Figure 14.1. Schematic diagram of the structure of an immunoglobulin G (IgG) molecule. The location and extent of intra- and interchain disulfide bonds varies with the host species and antibody subclass.

There are different classes and subclasses of immunoglobulins which are determined by the amino acid sequence of the light and heavy chains. 

Serum immunoglobulins, total IgG, and subclasses IgM, IgG, IgE (Luminex assay, ELISA)... 

The CSF/serum ratio of IgG eliminates the individual variation of serum IgG. The quotient of IgG (CSF/serum) to albumin (CSF/serum) eliminates the variation of the IgG quotient by the individual blood-CSF barrier function. Intrathecal IgG is total CSF IgG minus transudative IgG. The first formulas were based on a linear relationship between Q ib and Qigo (Cl, K3, LI, S4). More recent formulas make use of a hyperbolic or exponential function. The application of the latter two formulas reduces the number of false-positive results in the cases of blood-brain barrier disturbances, while sensitivity is maintained. Soeverijn compared Reiber s hyperbolic formula to five other formulas and showed that Reiber s formula produced the best agreement with the lEF gold standard (LI). For the latest modification of the IgG, IgA, and IgM subclasses of immunoglobulins, see Section 3.2.3. 

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