IgG Antibody

Immunoglobulin gamma (IgG) is the most common class of antibody in blood and extracellular fluid. Approximately 75% of serum antibodies in humans are IgG. There are four immunoglobulin gamma subclasses: one, two, three and four. IgG1 is the most common, with 68% of all gamma class antibodies being G1, and G4 is the least common at 4%. Gamma class antibodies are found primarily in the secondary immune response, class switching from IgM and IgD. They are the only class of antibody that can cross the placenta, and along with IgA secreted in breast milk, provide the neonate with humoral immunity before immune system development occurs.This antibody recognizes a protein of 75kDa identified as the gamma heavy chain of human immunoglobulins. It does not cross-react with alpha, mu, epsilon, or delta heavy chains, T-cells, monocytes, granulocytes, or erythrocytes. The IgG antibody is useful in the identification of leukemias, plasmacytomas, and certain non-Hodgkin's lymphomas. The most common feature of these malignancies is the restricted expression of a single heavy chain class. Demonstration of clonality in lymphoid infiltrates indicates that the infiltrate is clonal and therefore malignant.