Immunoglobulins are proteins produced by plasma cells to respond to an immunogen. How many main classes are there and which are they?

Immunoglobulins are proteins produced by plasma cells to respond to an immunogen. How many main classes are there and which are they?

• A. IgG, IgA, IgM, IgE, and IgD
• B. IgA, IgC, IgD, IgE
• C. IgG, IgH, IgK, IgL
• D. IgA, IgM, IgN, IgO

Answer: (A)

There are five main classes of immunoglobulins, defined by the heavy chain constant region, and they are IgG, IgA, IgM, IgD, and IgE. Each class serves different roles and resides in different parts of the body: IgG is the most abundant in serum and provides long-term protection; IgA is primarily in secretions like mucus, saliva, and tears; IgM is the first antibody produced in a primary response and often exists as a pentamer in circulation; IgD mainly functions as a B cell receptor on naïve B cells; and IgE is involved in allergic responses and defense against parasites. The other options mix non-existent isotypes (like IgC, IgH, IgK, IgL, IgN, IgO) or refer to light chains rather than whole antibody classes, so they aren’t correct.

There are five main classes of immunoglobulins, defined by the heavy chain constant region, and they are IgG, IgA, IgM, IgD, and IgE. Each class serves different roles and resides in different parts of the body: IgG is the most abundant in serum and provides long-term protection; IgA is primarily in secretions like mucus, saliva, and tears; IgM is the first antibody produced in a primary response and often exists as a pentamer in circulation; IgD mainly functions as a B cell receptor on naïve B cells; and IgE is involved in allergic responses and defense against parasites. The other options mix non-existent isotypes (like IgC, IgH, IgK, IgL, IgN, IgO) or refer to light chains rather than whole antibody classes, so they aren’t correct.