Question

Which of the following immunoglobulins is found as pentamer?
A. IgG
B. IgM
C. IgA
D. IgE

Answer 1

Hint: Immunoglobulin (Ig) or antibody is a broad, Y-shaped protein being used by the immune system to detect and neutralize foreign material like pathogenic microorganisms. The antibody recognizes a specific pathogen molecule called an antigen.

Complete answer:
Immunoglobulin M (IgM) is one of many antibody isotypes (also known as an immunoglobulin) that are formed by vertebrates. IgM is the largest antibody and the first antibody to appear in response to the initial exposure to the antigen. Immunoglobulin M is a protein of high molecular mass consisting of five or usually six sub-units. Monomers of IgM are contained at a small level in serum samples. Each pentamer IgM molecule consists of ten heavy (μ) chains, 10 light chains, and typically one junction (J) chain. IgM will be the first neonate-synthesized immunoglobulins which are the dominant class of immunoglobulin molecules that appear in the early phases of the immune reaction. In the monomeric type, IgM behaves as an enzyme part of the B-cell antigen receptor complex of non-stimulated B cells. IgM antibodies are generated as the body's first response to the new disease or "non-self" antigen, providing short-term defence. They raise for the next few weeks and then decline as IgG production progresses.

So, the correct answer is option (B).

Additional information:
Around 70-80 percent of the blood antibodies are IgG. Specific IgG antibodies produced during a primary outbreak or other antigen entry, rising a few weeks after beginning, then declining and maintaining. The body contains a list of IgG antibodies which can be quickly reproduced when subjected to the same antigen. IgE is linked with allergies, allergic disorders, and parasitic infections. It is often assessed as part of a blood panel allergy test. IgA is around 15% of the overall immunoglobulins in the blood but it is also found in saliva, tears, breathing and gastric secretions, and breast milk. IgA provides protection against disease in body mucosal areas including the respiratory tract, GI tract. When transmitted from mother to child through breast-feeding, it actually protects the intestinal tract of the child.

Note: Antibodies are glycoproteins contributing to the super-family of immunoglobulin. The terms antibody and immunoglobulin are used mostly interchangeably, although the term 'antibody' often is used for the secreted, soluble form. In order to allow the immune system to identify millions of different antigens, the antigen side chains at both antibody tips were extremely diverse.