Changes

[[Image:B-cell immunity.jpg|thumb|right|250pxl|B-cell differentiation - B. Catchpole, RVC 2008]]

[[Image:B-cell immunity.jpg|thumb|right|250pxl|B-cell differentiation - B. Catchpole, RVC 2008]]

==Introduction==

==Introduction==

<p>Mature [[B cells]] that undergo stimulation by an antigen undergo class switching, and differentiate into either '''plasma''' or '''memory''' cells. </p>

<p>Mature [[B cells]] that undergo stimulation by an antigen undergo class switching, and differentiate into either '''plasma''' or '''memory''' cells. </p>

<p>In the paracortex region of the [[Lymph Nodes - Anatomy & Physiology|lymph node]] binding to [[Major_Histocompatability_Complexes#MHC_II|MHC II]] in the presence of Il-4 produced by the [[Lymphocytes#Helper CD4+|CD4⁺ T cells]] (Th2 type) causes the B cells to differentiate; most will become plasma cells, however small number become memory cells.</p>

<p>In the paracortex region of the [[Lymph Nodes - Anatomy & Physiology|lymph node]] binding to [[Major_Histocompatability_Complexes#MHC_II|MHC II]] in the presence of IL-4 produced by the [[Lymphocytes#Helper CD4+|CD4⁺ T cells]] (T_H2 type) causes the B cells to differentiate; most will become plasma cells, however a small number will become memory cells.</p>

Follicular dendritic cells present in the germinal centers of peripheral lymphoid organs can absorb intact antigen onto their surface to present to B cells to stimulate differentiation.

Follicular dendritic cells present in the germinal centers of peripheral lymphoid organs can absorb intact antigen onto their surface to present to B cells to stimulate differentiation.

==Plasma cells==

==Plasma cells==

===Appearance===

===Appearance===

<p>Plasma cells are oval, around 9µm and have a round prominent nucleus. The cytoplasm is extensive and strongly basophilic when stained. It contains large amounts of rough endoplasmic reticulum and the Golgi apparatus is large and appears as a clear crescent-shaped structure near the nucleus. Some plasma cells accumulate considerable quantities of, perhaps abnormal, antibody and this appears as a large eosinophilic blob filling the cytoplasm and displacing the nucleus to one side. These blobs are called "Russell Bodies".</p>

<p>Plasma cells are oval, around 9µm and have a round prominent nucleus. The cytoplasm is extensive and strongly basophilic when stained. It contains large amounts of rough endoplasmic reticulum and the Golgi apparatus is large and appears as a clear crescent-shaped structure near the nucleus. Some plasma cells, known as '''"Mott cells"''', accumulate considerable quantities of, perhaps abnormal, antibody and this appears as a large eosinophilic blob filling the cytoplasm and displacing the nucleus to one side. These blobs are called '''"Russell Bodies"'''.</p>

===Function===

===Function===

===Class switching===

===Class switching===

<p>Initially plasma cell produce [[Immunoglobulin M|Immunoglobulin M (IgM)]] however this is not always the most appropriate Ig to be produced and therefore stimulation by [[Lymphocytes#Helper CD4+|T cells]] and interleukins causes the plasma cells to undergo class switching to produce different classes of Immunoglobulins.

<p>Initially plasma cell produce [[Immunoglobulin M|Immunoglobulin M (IgM)]] however this is not always the most appropriate Ig to be produced and therefore stimulation by [[Lymphocytes#Helper CD4+|T cells]] and interleukins causes the plasma cells to undergo class switching to produce different classes of Immunoglobulins.

*In mucosal B cells plasma cells CD40 interaction (with Th2 CD40L) and Il-10 stimulates class switching to [[Immunoglobulin A|IgA]]

*In mucosal B cells plasma cells CD40 interaction (with T_H2 CD40L) and Il-10 stimulates class switching to [[Immunoglobulin A|IgA]]

*[[Eosinophils|Eosinophils]] produce Il-13 which promotes class switching to [[Immunoglobulin E|IgE]]</p>

*[[Eosinophils|Eosinophils]] produce Il-13 which promotes class switching to [[Immunoglobulin E|IgE]]</p>

<p>Plasma cells produced in the first immune response to an antigen are mainly of the class IgM whereas those produced from memory cells in the second immune response are mainly of the [[Immunoglobulin G|IgG]] class.</p>

<p>Plasma cells produced in the first immune response to an antigen are mainly of the class IgM whereas those produced from memory cells in the second immune response are mainly of the [[Immunoglobulin G|IgG]] class.</p>

<p>Memory cells are long lived and responsible for long term immunity providing the immune system with a memory of previously encountered antigens. When they experience an antigen again they proliferate and differentiate into plasma cells. This response produces up to ten times more plasma cells than the original exposure to the antigen and is why the second immune response to an antigen is both more rapid and much stronger than the first response.</p>

<p>Memory cells are long lived and responsible for long term immunity providing the immune system with a memory of previously encountered antigens. When they experience an antigen again they proliferate and differentiate into plasma cells. This response produces up to ten times more plasma cells than the original exposure to the antigen and is why the second immune response to an antigen is both more rapid and much stronger than the first response.</p>

[[Category:Lymphocytes|C]]

[[Category:Lymphocytes|C]]

[[Category:Adaptive Immune System]]

[[Category:Adaptive Immune System]]