Immunoglobulins properties

Factor VIII, immunoglobulin, and albumin are all held as protein precipitates, the first as cryoprecipitate and the others as the Cohn fractions FI + II + III (or FII + III) and FIV + V (or FV), respectively (Table 7, Fig. 2). Similarly, Fractions FIVj + FIV can provide an intermediate product for the preparation of antithrombin III and a-1-proteinase inhibitor. This abiUty to reduce plasma to a number of compact, stable, intermediate products, together with the bacteriacidal properties of cold-ethanol, are the principal reasons these methods are stiU used industrially. 

Table 10. Properties of Normal Immunoglobulin and Intravenous Immunoglobulin...

The basic structure of all immunoglobulin (Ig) molecules comprises two identical light chains and two identical heavy chains linked together by disulfide bonds (Figure IS.2a). There are two different classes, or isotypes, of light chains, X and k, but there is no known functional distinction between them. Heavy chains, by contrast, have five different isotypes that divide the immunoglobulins into different functional classes IgG, IgM, IgA, IgD, and IgE, each with different effector properties in the elimination of antigen... 

The 3 subunits ((31 -(34) are membrane proteins with a single transmembrane domain and an extracellular immunoglobulin-like motif, and perform the regulatory roles of the sodium channel. The (31 subunit accelerates the activation and inactivation kinetics. The (32 subunit is covalently linked to the a subunit, and is necessary for the efficient assembly of the channel. The more recently identified (33 subunit is homologous to (31, but differs in its distribution within the brain and in a weaker accelerating property. The (34 subunit is similar to (32 and is covalently linked to the a subunit. 

The fundamental role of blood in the maintenance of homeostasis and the ease with which blood can be obtained have meant that the study of its constituents has been of central importance in the development of biochemistry and clinical biochemistry. The basic properties of a number of plasma proteins, including the immunoglobulins (antibodies), are described in this chapter. Changes in the amounts of various plasma proteins and immunoglobulins occur in many diseases and can be monitored by electrophoresis or other suitable procedures. As indicated in an earlier chapter, alterations of the activities of certain enzymes found in plasma are of diagnostic use in a number of pathologic conditions. 

Antibody classes In mammals, there are five classes of antibodies (also known as immunoglobulins IgG, IgA, IgM, IgE and IgD). Each immunoglobulin class differs in their heavy chain constant domains (see Fig. 1.2) and consequently in its biological properties. For immunoassays, two immuno-glubulin classes are of importance - IgG and IgM. 

Immunoglobulins in the form of monoclonal antibodies are manufactured commercially for therapeutic and diagnostic uses. Major areas of consideration in these applications are quality control and bioactivity. Separation of immunoglobulins has proven to be a challenge even for well-established techniques such as HPLC. Difficulties arise due to the large size of antibodies and their surface properties, which increase their tendency to interact with proteins and matrix. 

Soluble antigen receptors, which are formed by activated B cells (plasma cells see p. 294) and released into the blood, are known as antibodies. They are also members of the immunoglobulin family (Ig see p. 296). Antibodies are an important part of the humoral immune defense system. They have no antimicrobial properties themselves, but support the cellular immune system in various ways ... 

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