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==='''Promotion of phagocytosis'''===

==='''Promotion of phagocytosis'''===

Antibodies also have a function to facilitate phagocytosis. Phagocytes have receptors for the Fc portion of antibody, using FcR receptors. FcR bind the Fc portion of antibody on antigen/antibody complexes, although the antibody alone does not interact with FcR. Interaction of FcR with Ab/Ag complexes stimulates '''cellular activation''' which greatly increases the efficiency of phagocytosis. This process is called '''opsonisation'''. Opsonisation promotes the '''production of intracellular enzymes''' and therefore promotes the killing and digestion of internalised micro organisms. Systems used by phagocytes that are important in intracellular killing include free radicals such as oxygen and chlorine, hydrogen peroxidase and nitric oxide produced by nitric oxide synthase. Ultimately phagocytes undergo '''degranulation''' resulting in the '''secretion of certain enzymes and cytotoxic molecules'''. These systems are also activated by the interferons, especially the immune interferon – IFN & gamma. Antibody-mediated opsonisation of micro organisms is much more efficient that innate immune system receptors. Phagocytes also have receptors for iC3b, a [[Complement|complement]] component which is also a major initiator of opsonisation.

Antibodies also have a function to facilitate phagocytosis. Phagocytes have receptors for the Fc portion of antibody, using FcR receptors. FcR bind the Fc portion of antibody on antigen/antibody complexes, although the antibody alone does not interact with FcR. Interaction of FcR with Ab/Ag complexes stimulates '''cellular activation''' which greatly increases the efficiency of phagocytosis. This process is called '''opsonisation'''. Opsonisation promotes the '''production of intracellular enzymes''' and therefore promotes the killing and digestion of internalised micro organisms. Systems used by phagocytes that are important in intracellular killing include free radicals such as oxygen and chlorine, hydrogen peroxidase and nitric oxide produced by nitric oxide synthase. Ultimately phagocytes undergo '''degranulation''' resulting in the '''secretion of certain enzymes and cytotoxic molecules'''. These systems are also activated by the interferons, especially the immune interferon – IFN & gamma. Antibody-mediated opsonisation of micro organisms is much more efficient that innate immune system receptors. Phagocytes also have receptors for iC3b, a [[Complement|complement]] component which is also a major initiator of opsonisation.

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* '''&alpha; chain - [[IgA]]'''  

* '''&alpha; chain - [[IgA]]'''  

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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 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.

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[[Category:Immunoglobulins|A]]

[[Category:Immunoglobulins|A]]

[[Category:To Do - Review]]

[[Category:A&P Done]]