immunoglobulin-M (IgM)

Function: - IgM antibodies play an important role in primary defense mechanisms - role in early recognition of external invaders like bacteria & viruses, cellular waste & modified self, as well as in recognition & elimination of precancerous & cancerous lesions. - the membrane-bound form is found in the majority of normal B cells alongside with IgD - membrane-bound IgM induces the phosphorylation of CD79A & CD79B by the Src family of protein tyrosine kinases - membrane-bound IgM is non-covalently associated with heterodimer of CD79A & CD79B - it may cause death of cells by apoptosis - it is also found in soluble form, representing ~30% of the total serum immunoglobulins where it is found almost exclusively as a homopentamer - after the antigen binds to the B cell receptor, the secreted form is secreted in large amounts - IgM strongly fixes complement (4+) by the classical pathway Laboratory: - IgM in tissue - IgM in blood - IgM in CSF - IgM monoclonal in CSF - IgM in peritoneal fluid - IgM in serum - IgM monoclonal in serum - IgM in urine

Related

complement-fixing antibody IgM Ag in skin IgM in body fluid

General

immunoglobulin oligomerizing protein

Properties

CONFIGURATION: pentamer SUBUNITS: immunoglobulin mu chain (Ig-mu, IGHM) (2) MOTIF: Ig heavy chain variable region NAME: Ig heavy chain variable region heavy chain constant region-1 MOTIF: cysteine residue {CH1.SITE1} MODIFICATION: cysteine residue {CH1.SITE2} cysteine residue {CH1.SITE2} MODIFICATION: cysteine residue {CH1.SITE1} cysteine residue {C-TO-CH1} MODIFICATION: cysteine residue {C-TO-CL} hinge region MOTIF: cysteine residue {HINGE1} MODIFICATION: cysteine residue {HINGE1} cysteine residue {HINGE2} MODIFICATION: cysteine residue {HINGE2} heavy chain constant region-2 MOTIF: cysteine residue {CH2.SITE1} MODIFICATION: cysteine residue {CH2.SITE2} cysteine residue {CH2.SITE2} MODIFICATION: cysteine residue {CH2.SITE1} heavy chain constant region-3 MOTIF: cysteine residue {CH3.SITE1} MODIFICATION: cysteine residue {CH3.SITE2} cysteine residue {CH3.SITE2} MODIFICATION: cysteine residue {CH3.SITE1} heavy chain constant region-4 MOTIF: cysteine residue {CH4.SITE1} MODIFICATION: cysteine residue {CH4.SITE2} cysteine residue {CH4.SITE2} MODIFICATION: cysteine residue {CH4.SITE1} immunoglobulin light chain (2) MOTIF: Ig light chain variable region NAME: Ig light chain variable region light chain constant region MOTIF: cysteine residue {CLSITE1} MODIFICATION: cysteine residue {CL.SITE2} cysteine residue {CL.SITE2} MODIFICATION: cysteine residue {CL.SITE1} cysteine residue {C-TO-CL} MODIFICATION: cysteine residue {C-TO-CH1} SIZE: MW = 900 kD COMPARTMENT: plasma SECRETED-BY: plasma cell MISC-INFO: CONCENTRATION 25-200 MG/DL

Components

immunoglobulin light chain immunoglobulin mu chain (Ig-mu, IGHM)