Changes

**** 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

* 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

==Clinical Uses==

==Clinical Uses==