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ページの作成:「{{Floating_Menu}} ==Immunoglobulin molecule== →免疫グロブリンとは#分子としての免疫グロブリン immunoglobulin ==Immunoglobulin as B cell recep…」
{{Floating_Menu}}
==Immunoglobulin molecule==
→[[免疫グロブリンとは#分子としての免疫グロブリン immunoglobulin]]
==Immunoglobulin as B cell receptor==
<table>
<tr>
<td>
{{#mermaid:
flowchart LR
p([Pathogen])
}}
</td>
<td colspan="3">
{{#mermaid:
flowchart LR
ig[Ig] --- fr[Fc receptor] --- bc[B cell]
}}
</td>
</tr>
<tr>
<td colspan="4">
{{#mermaid:
flowchart LR
p([Pathogen]) --- ig[Ig] --- fr[Fc receptor] --- bc[B cell]
}}
</td>
</tr>
<tr>
<td colspan="3">
{{#mermaid:
flowchart LR
p([Pathogen]) --- ig[Ig]
}}
</td>
<td>
{{#mermaid:
flowchart LR
fr[Fc receptor] --- pc["B cell→<br>Plasma cell"] -.- a1((Ig=Ab)) & a2((Ig=Ab)) & a3((Ig=Ab))
}}
</td>
</tr>
</table>
==Primary and secondary responses of B cell==
{|class="wikitable"
|-
!
!Primary
!Secondary
|-
!Type
|Naive B cell
|Memory B cell
|-
!Lag time
|4-7 days
|1-3 days
|-
!Peak
|7-10 days
|3-6 days
|-
!Intensity
|Varies
|100-1000 times<br>higher than primary
|-
!Ig class
|IgM
|IgG
|-
!Antigen
|T-cell independent
|T-cell dependent
|-
!Affinity
|Low
|High
|}
==B cell activation by cross-linking==
*Cross-linking of multiple B cell receptors (immunoglobulins) by antigen is needed to activate B cell intracellular signaling
===T cell independent antigens===
*Antigen with repetitive structure (e.g., lipopolysaccharides) cross-link B cell receptors in wider ranges as well as non-BCR structures on B cell surface, resulting in activation of B cell without T cell (T cell independent antigen)
===T cell dependent antigens===
*Antigen of proteins cross-link B cell receptors but at the same time needs antigen presentation by TCR of CD4+ T cell onto pMHC class II on B cell via CD28 and/or CD40 co-stimulation
{{#mermaid:
flowchart LR
subgraph b[B cell]
m2[pMHC class II] --- b1[B cell] --- BCR
CD80 --- b1
CD40 --- b1
end
subgraph t[CD4+ T cell]
direction LR
t1[T cell] --- TCR
t1 --- CD28
t1 --- CD154
end
CD28 -.- CD80
CD154 -.- CD40
TCR -.- a2[Antigen] -.- m2
BCR -.- a1[Antigen]
}}
{|class="wikitable"
|-
!
!T independent
!T dependent
|-
!Antigen
|Repetitive structure
|Protein
|-
!Ig class switching
|Little→IgM main
|Induce→IgG
|-
!Affinity maturation
|Doesn't occur
|Occur
|-
!B cell memory
|No
|Yes
|-
!B cell longevity
|Long plasma cell
|Short plasma cell
|}
==Affinity maturation at germinal center==
*Somatic hypermutation at dark zone of lymph nodes
**Activation-induced cytidine deaminase (AID) induces random point mutations on V regions of both of heavy chain and light chain
*Affinity maturation at light zone of LN
**Follicular dendritic cells present antigens to select only B cells that randomly obtained affinitive BCR (Ig)
==Immunoglobulin molecule==
→[[免疫グロブリンとは#分子としての免疫グロブリン immunoglobulin]]
==Immunoglobulin as B cell receptor==
<table>
<tr>
<td>
{{#mermaid:
flowchart LR
p([Pathogen])
}}
</td>
<td colspan="3">
{{#mermaid:
flowchart LR
ig[Ig] --- fr[Fc receptor] --- bc[B cell]
}}
</td>
</tr>
<tr>
<td colspan="4">
{{#mermaid:
flowchart LR
p([Pathogen]) --- ig[Ig] --- fr[Fc receptor] --- bc[B cell]
}}
</td>
</tr>
<tr>
<td colspan="3">
{{#mermaid:
flowchart LR
p([Pathogen]) --- ig[Ig]
}}
</td>
<td>
{{#mermaid:
flowchart LR
fr[Fc receptor] --- pc["B cell→<br>Plasma cell"] -.- a1((Ig=Ab)) & a2((Ig=Ab)) & a3((Ig=Ab))
}}
</td>
</tr>
</table>
==Primary and secondary responses of B cell==
{|class="wikitable"
|-
!
!Primary
!Secondary
|-
!Type
|Naive B cell
|Memory B cell
|-
!Lag time
|4-7 days
|1-3 days
|-
!Peak
|7-10 days
|3-6 days
|-
!Intensity
|Varies
|100-1000 times<br>higher than primary
|-
!Ig class
|IgM
|IgG
|-
!Antigen
|T-cell independent
|T-cell dependent
|-
!Affinity
|Low
|High
|}
==B cell activation by cross-linking==
*Cross-linking of multiple B cell receptors (immunoglobulins) by antigen is needed to activate B cell intracellular signaling
===T cell independent antigens===
*Antigen with repetitive structure (e.g., lipopolysaccharides) cross-link B cell receptors in wider ranges as well as non-BCR structures on B cell surface, resulting in activation of B cell without T cell (T cell independent antigen)
===T cell dependent antigens===
*Antigen of proteins cross-link B cell receptors but at the same time needs antigen presentation by TCR of CD4+ T cell onto pMHC class II on B cell via CD28 and/or CD40 co-stimulation
{{#mermaid:
flowchart LR
subgraph b[B cell]
m2[pMHC class II] --- b1[B cell] --- BCR
CD80 --- b1
CD40 --- b1
end
subgraph t[CD4+ T cell]
direction LR
t1[T cell] --- TCR
t1 --- CD28
t1 --- CD154
end
CD28 -.- CD80
CD154 -.- CD40
TCR -.- a2[Antigen] -.- m2
BCR -.- a1[Antigen]
}}
{|class="wikitable"
|-
!
!T independent
!T dependent
|-
!Antigen
|Repetitive structure
|Protein
|-
!Ig class switching
|Little→IgM main
|Induce→IgG
|-
!Affinity maturation
|Doesn't occur
|Occur
|-
!B cell memory
|No
|Yes
|-
!B cell longevity
|Long plasma cell
|Short plasma cell
|}
==Affinity maturation at germinal center==
*Somatic hypermutation at dark zone of lymph nodes
**Activation-induced cytidine deaminase (AID) induces random point mutations on V regions of both of heavy chain and light chain
*Affinity maturation at light zone of LN
**Follicular dendritic cells present antigens to select only B cells that randomly obtained affinitive BCR (Ig)
