Changes

* '''α chain - [[IgA]]'''

* '''α chain - [[IgA]]'''

<br />

<br />

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''. 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 and 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 variable domain. After antigenic exposure the [[IgM]]+ B-cells differentiate and begin to synthesise other classes of immunoglobulin, but only under the '''direct influence of a T-cell'''. This system is known as '''immunoglobulin heavy chain switching'''. 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. Under the influence of T-cells, B-cells undergo immunoglobulin heavy chain switching and the B-cells mature from [[IgM]] to [[IgG]] producers and IgE and IgA producers can also be generated. These immunoglobulins tend to be produced within lymphoid tissue associated with mucosal surfaces.

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''. 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 and 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 variable domain. After antigenic exposure the [[IgM]]+ B-cells differentiate and begin to synthesise other classes of immunoglobulin, but only under the '''direct influence of a T-cell'''. This system is known as '''immunoglobulin heavy chain switching'''. 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. Under the influence of T-cells, B-cells undergo immunoglobulin heavy chain switching and the B-cells mature from [[IgM]] to [[IgG]] producers and IgE and IgA producers can also be generated. These immunoglobulins tend to be produced within lymphoid tissue associated with mucosal surfaces.

<br />

<br />

<br />

<br />