Author, Bureaucrats, Administrators
12,693
edits
Changes
New page: <p>Mature B cells that undergo stimulation by an antigen undergo class switching, and differentiate into either plasma or [[#Memory ce...
<p>Mature [[Lymphocytes - WikiBlood#B cells|B cells]] that undergo stimulation by an antigen undergo class switching, and differentiate into either [[#Plasma cells|plasma]] or [[#Memory cells|memory]] cells. </p>
<p>In the paracortex region of [[Lymph Nodes - Anatomy & Physiology|lymph nodes]] binding to MHC II and the presence of Il-4 produced by [[Lymphocytes - WikiBlood#Helper CD4+|CD4<sup>+</sup> T cells]] (Th2 type) causes [[Lymphocytes - WikiBlood#B cells|B cells]] to differentiate. Most [[Lymphocytes - WikiBlood#B cells|B cells]] become [[#Plasma cells|plasma cells]], however small number become [[#Memory cells|memory cells]] .</p>
==Plasma cells==
===Appearance===
<p>Plasma cells are oval, around 9µm and have a round prominent nucleus. The cytoplasm is extensive and stains strongly basophilic. 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>
===Function===
<p>Plasma cells produce immunoglobulins/antibodies (thousands a second). The immunoglobulin binding specificity is identical to the binding specificity of the BCR on the [[Lymphocytes - WikiBlood#B cells|B cell]] that the cell has differentiated from. This means that when a [[Lymphocytes - WikiBlood#B cells|B cell]] has a BCR that can effectively bind to an antigen the immunoglobulins produced by the plasma cell can bind to that antigen.</p>
<p>Although they can live for months most plasma cells only live for a few days and do not replicate in this time.</p>
===Class switching===
<p>Initially plasma cell produce IgM however this is not always the most appropriate Ig to be produced and therefore stimulation by [[Lymphocytes - WikiBlood#Helper CD4+|T cells]] and interleukins causes the plasma cells to undergo class switching to produce different classes of Ig.
*In mucosal B cells plasma cells CD40 interaction (with Th2 CD40L) and Il-10 stimulates class switching to IgA
*[[Eosinophils - WikiBlood|Eosinophils]] produce Il-13 which promotes class switching to 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 IgG class.</p>
===In pathology===
*[[General Pathology - Changes in Inflammatory Cells Circulating in Blood#Plasma Cells|Plasma cell tumour]]
==Memory cells==
<p>The differentiated cells that remain in the cortex become memory cells and these proliferate and form germinal centres in the [[Lymph Nodes - Anatomy & Physiology|lymph node]].</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>In the paracortex region of [[Lymph Nodes - Anatomy & Physiology|lymph nodes]] binding to MHC II and the presence of Il-4 produced by [[Lymphocytes - WikiBlood#Helper CD4+|CD4<sup>+</sup> T cells]] (Th2 type) causes [[Lymphocytes - WikiBlood#B cells|B cells]] to differentiate. Most [[Lymphocytes - WikiBlood#B cells|B cells]] become [[#Plasma cells|plasma cells]], however small number become [[#Memory cells|memory cells]] .</p>
==Plasma cells==
===Appearance===
<p>Plasma cells are oval, around 9µm and have a round prominent nucleus. The cytoplasm is extensive and stains strongly basophilic. 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>
===Function===
<p>Plasma cells produce immunoglobulins/antibodies (thousands a second). The immunoglobulin binding specificity is identical to the binding specificity of the BCR on the [[Lymphocytes - WikiBlood#B cells|B cell]] that the cell has differentiated from. This means that when a [[Lymphocytes - WikiBlood#B cells|B cell]] has a BCR that can effectively bind to an antigen the immunoglobulins produced by the plasma cell can bind to that antigen.</p>
<p>Although they can live for months most plasma cells only live for a few days and do not replicate in this time.</p>
===Class switching===
<p>Initially plasma cell produce IgM however this is not always the most appropriate Ig to be produced and therefore stimulation by [[Lymphocytes - WikiBlood#Helper CD4+|T cells]] and interleukins causes the plasma cells to undergo class switching to produce different classes of Ig.
*In mucosal B cells plasma cells CD40 interaction (with Th2 CD40L) and Il-10 stimulates class switching to IgA
*[[Eosinophils - WikiBlood|Eosinophils]] produce Il-13 which promotes class switching to 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 IgG class.</p>
===In pathology===
*[[General Pathology - Changes in Inflammatory Cells Circulating in Blood#Plasma Cells|Plasma cell tumour]]
==Memory cells==
<p>The differentiated cells that remain in the cortex become memory cells and these proliferate and form germinal centres in the [[Lymph Nodes - Anatomy & Physiology|lymph node]].</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>