Which are the five antibody isotypes in humans?

Which are the five antibody isotypes in humans?

• A. IgA, IgD, IgE, IgG, IgM
• B. IgA, IgB, IgC, IgD, IgE
• C. IgG, IgA, IgM
• D. IgA, IgG, IgM, IgK, IgL

Answer: (A)

Antibodies in humans are classified into five isotypes based on the heavy-chain constant regions, which determine their distinct functions and distribution. The five isotypes are IgA, IgD, IgE, IgG, and IgM. IgA is abundant in mucosal secretions (tears, saliva, mucus) and in breast milk, providing frontline defense on mucosal surfaces. IgD mostly serves as the B cell receptor on naive B cells. IgE is involved in defense against parasites and in allergic reactions by activating mast cells and basophils. IgG is the most prevalent in blood and tissues and mediates neutralization, opsonization, and complement activation. IgM appears early during an immune response as a pentamer, great for agglutination and initial complement activation. The other options are not correct because they include non-existent isotypes (IgB, IgC, IgK, IgL) or omit one or more real isotypes (e.g., missing IgD or IgE), or confuse light chains with whole isotypes.

Antibodies in humans are classified into five isotypes based on the heavy-chain constant regions, which determine their distinct functions and distribution. The five isotypes are IgA, IgD, IgE, IgG, and IgM.

IgA is abundant in mucosal secretions (tears, saliva, mucus) and in breast milk, providing frontline defense on mucosal surfaces. IgD mostly serves as the B cell receptor on naive B cells. IgE is involved in defense against parasites and in allergic reactions by activating mast cells and basophils. IgG is the most prevalent in blood and tissues and mediates neutralization, opsonization, and complement activation. IgM appears early during an immune response as a pentamer, great for agglutination and initial complement activation.

The other options are not correct because they include non-existent isotypes (IgB, IgC, IgK, IgL) or omit one or more real isotypes (e.g., missing IgD or IgE), or confuse light chains with whole isotypes.