ANATOMY

Detailed explanation-1: -IgG is synthesized mostly in the secondary immune response to pathogens. IgG can activate the classical pathway of the complement system, and it also is highly protective. The four subclasses of IgG include IgG1, IgG2, IgG3, and IgG4. IgG1 is around 65% of the total IgG.

Detailed explanation-2: -Of the five immunoglobulin isotypes, immunoglobulin G (IgG) is most abundant in human serum.

Detailed explanation-3: -IgG, a monomer, is the predominant Ig class present in human serum. Produced as part of the secondary immune response to an antigen, this class of immunoglobulin constitutes approximately 75% of total serum Ig.

Detailed explanation-4: -Isotypes of Immunoglobulins IgG is the most abundant circulating antibody, making up 80% of the total antibodies and 75% of that found in serum. IgG provides the majority of antibody-based immunity against pathogens.

Detailed explanation-5: -Normal serum levels-IgA is the second most abundant isotype in the circulation, following immunoglobulin G (IgG) [4-8]. IgA levels, generally absent at birth, gradually increase throughout the first year of life to about 30 percent of adult levels at one year.