Membrane immunoglobulin

A B-lymphocyte can simultaneously express membrane immunoglobulin as IgM (monomeric) or IgD with the same variable region (i.e., antigen-binding site). The B-lymphocyte then can secrete different isotypes [e.g., IgM... 

Each immunoglobulin class exists in two forms - as secreted and membrane-bound antibody. Membrane exons code for the transmembrane and cytoplasmic portion of membrane immunoglobulin and replace the secretory termini the transmembrane portion itself consists of a stretch of hydrophobic amino acids [107, 108,109,110,111,112,113],... 

Glomerulonephritis induced by by sensitization to heterologous immunoglobulin prior to administration of heterologous anti-glomerular basement membrane immunoglobulin (BALB/c). 

Affinity chromatography of surface glycoproteins and immunoglobulin E receptors from rat basophilic leukaemia cells Affinity chromatography of membrane immunoglobulin M and murine lymphocyte immunoglobulin study of their affinities for the lectin... 

Several hypotheses have been suggested to explain the occurrence of IgM and IgD as both secreted (aqueous-soluble) and membrane-bound proteins. Any explanation must account for the fact that membrane immunoglobulins which have been extracted with detergent are insoluble in physiological buffers in the absence of detergents (or some other dena-turant) i.e., membrane IgM and IgD are to a degree hydrophobic (Melcher et aL, 1975) while the secreted form is not. Possible explanations which have been suggested are that (1) the two forms differ in sequence, (2) a separate insertional piece is added to the membrane form, or (3) the conformation of the membrane-associated position of the molecule differs from that of its soluble counterpart. The membrane-favored conformation would have to be maintained in a polar medium to... 

Whatever the mode of attachment of SIg to cell membranes, the major portion of the Fc part of the molecule is not embedded in the phospholipid bilayer. This is also supported by the fact that CD spectra of all membrane proteins (not lymphocytes specifically) show little conformation, which, as previously mentioned, is the conformation of immunoglobulin domains. Experiments with reconstituted lymphocyte plasma membranes (Chavin and Holliman, 1975) and model membrane systems (Weissman et al., 1974) have not, in general, been very revealing. With reconstituted membranes, very little of the original membrane immunoglobulin becomes reincorporated. Liposome models were tested by... 

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