ig
immunoglobulins
introduction
IgA
a type of immunoglobulin that protects against infections of the mucous membranes lining the mouth, airways, and digestive tract
serum IgA levels may be raised due to:
IgE
IgG
composed of two identical heavy (CH) chains and two identical light (L) chains
usually have 2 identical antigen binding sites (on the Fab arms)
the amino acid sequences of the various IgG subclasses are 90 to 95 percent homologous
CH regions are encoded by C gene segments clustered on chromosome 14
four subclasses: IgG1, IgG2, IgG3, and IgG4
functional differences among the subclasses result from structural variation in both the Fc regions and the hinge regions
IgG1 and IgG3 fix C1q most effectively, IgG2 weakly, and IgG4 not at all
the Fc region is important in binding to phagocyte membrane Fc receptors and in initiating phagocytosis following “opsonization” of the target antigen by it being bound to IgG
60-70% of serum IgG is IgG1, 20-30% is IgG2, 5-8% is IgG3 and 1-4% is IgG4
half-lives are ~ 21 days although IgG3 half-life is only ~9 days
serum IgG levels may be raised due to:
IgM
immunoglobulin production diseases or gammopathies
excess production
deficiency or dysgammaglobulinemia
X-linked agammaglobulinemia
complete lack of circulating B cells; 1 in 100,000 male newborns; Dx usually after a history of recurrent infections, mostly in the respiratory tract, through childhood
transient hypogammaglobulinemia of infancy
IgA deficiency
mild illness, mostly asymptomatic but increased risk of infections such as sinusitis, chest infections and UTI
risk of anaphylaxis to blood transfusions or intravenous immunoglobulin due to the presence of IgA in these blood products
higher risk of developing autoimmune diseases in middle age
1 in 300 people;
IgG sub-class deficiencies
isolated primary IgM deficiency
common variable immunodeficiency
immunodeficiency–centromeric instability–facial anomalies syndrome (ICF) syndrome
ig.txt · Last modified: 2020/08/18 17:37 by gary1