Changes

!width="200"|IgE

!width="200"|IgE

!width="200"|IgG

!width="200"|IgG

!width="200"|IgM

!width="200"|[[IgM]]

|-align="middle"  

|-align="middle"  

!Weight (kDa)

!Weight (kDa)

*** There are four different types of heavy chain constant domains - μ, γ, ε, α

*** There are four different types of heavy chain constant domains - μ, γ, ε, α

**** Different heavy chains are associated with different classes of antibody

**** Different heavy chains are associated with different classes of antibody

***** '''μ chain - IgM '''

***** '''μ chain - [[IgM]] '''

***** '''γ chain -IgG'''

***** '''γ chain -IgG'''

***** '''ε chain - IgE'''

***** '''ε chain - IgE'''

***** '''α chain - IgA'''  

***** '''α chain - IgA'''  

*** In humans and mice there exists a fifth Ig class, '''IgD (δ chain)'''

*** In humans and mice there exists a fifth Ig class, '''IgD (δ chain)'''

**** IgD is always expressed on B-cell membranes with IgM but is ''never secreted''

**** IgD is always expressed on B-cell membranes with [[IgM]] but is ''never secreted''

* The sequence of constant region genes on the chromosome is M, G, E and A

* The sequence of constant region genes on the chromosome is M, G, E and A

** In humans/ rodents the Cδ (IgD) is immediately downstream of the M gene

** In humans/ rodents the Cδ (IgD) is immediately downstream of the M gene

* Prior to antigenic stimulation, B-cells express cell membrane-associated IgM

* Prior to antigenic stimulation, B-cells express cell membrane-associated [[IgM]]

** The first immunoglobulin produced during an immune response is '''always IgM''' because the Cμ gene is the first constant H chain gene downstream of the the variable domain

** The first immunoglobulin produced during an immune response is '''always [[IgM]]''' because the Cμ gene is the first constant H chain gene downstream of the the variable domain

* After antigenic exposure the IgM+ B-cells differentiate

* After antigenic exposure the [[IgM]]+ B-cells differentiate

** Begin to synthesise other classes of immunoglobulin

** Begin to synthesise other classes of immunoglobulin

*** Only under the '''direct influence of a T-cell'''

*** Only under the '''direct influence of a T-cell'''

* There are also two possible light chains

* There are also two possible light chains

** There are no functional consequences for either type

** There are no functional consequences for either type

* The IgG antibodies produced in both primary and secondary responses originate from the same clones of B-cells as the IgM antibodies

* The IgG antibodies produced in both primary and secondary responses originate from the same clones of B-cells as the [[IgM]] antibodies

* The different antibody classes have the same variable domain combinations, and therefore the same antigenic specificity

* The different antibody classes have the same variable domain combinations, and therefore the same antigenic specificity

** Under the influence of T-cells, B-cells undergo immunoglobulin heavy chain switch

** Under the influence of T-cells, B-cells undergo immunoglobulin heavy chain switch

*** The B-cells mature from IgM to IgG producers

*** The B-cells mature from [[IgM]] to IgG producers

* IgE and IgA producers can be generated

* IgE and IgA producers can be generated

** These immunoglobulins tend to be produced within lymphoid tissue associated with mucosal surfaces

** These immunoglobulins tend to be produced within lymphoid tissue associated with mucosal surfaces