<prompt> The serum concentration of which of the following human IgG subclasses is maximum?IgG1IgG2IgG3IgG4  <response>: IgG is the major class of immunoglobulin present in the serum. The IgG molecule consists of two L chains and two H chains H2L2. There are four subclasses of IgG: IgG1, IgG2, IgG3, and IgG4. Each subtype contains a distinct but related H chain and each differs somewhat regarding their biological activities. IgG1 represents 65 of the total IgG.IgG2- 23, IgG3 -8 and IgG4 - 4Reference: Jawetz, Melnick, Adelbergs Medical Microbiology; 27th edition; Chapter 8; Immunology 