Διαφορά μεταξύ των αναθεωρήσεων του «Χρήστης:Dmtrs32/πρόχειρο»

 
==Activation==
[[File:B cell activation naive to plasma cell.png|thumb|BΕνεργοποίηση cellκυττάρων activationΒ: fromαπό immatureανώριμα BΒ cellκύτταρα toσε plasmaκύτταρα cellπλάσματος orή memoryΒ Bκύτταρα cell]]μνήμης
B cell activation: from immature B cell to plasma cell or memory B cell]]
B cell activation occurs in the [[secondary lymphoid organs]] (SLOs), such as the [[spleen]] and [[lymph nodes]].<ref name=":0" /> After B cells mature in the bone marrow, they migrate through the blood to SLOs, which receive a constant supply of antigen through circulating [[lymph]].<ref>{{Cite journal|title = Early Events in B Cell Activation|journal = Annual Review of Immunology|date = 2010-01-01|pmid = 20192804|pages = 185–210|volume = 28|issue = 1|doi = 10.1146/annurev-immunol-030409-101216|first1 = Naomi E.|last1 = Harwood|first2 = Facundo D.|last2 = Batista}}</ref> At the SLO, B cell activation begins when the B cell binds to an antigen via its BCR.<ref name=":7">{{Cite journal|title = How B cells capture, process and present antigens: a crucial role for cell polarity|journal = Nature Reviews Immunology|date = 2013-01-01|volume = 13|issue = 7|pages = 475–86|doi = 10.1038/nri3469|pmid = 23797063|first1 = Maria-Isabel|last1 = Yuseff|first2 = Paolo|last2 = Pierobon|first3 = Anne|last3 = Reversat|first4 = Ana-Maria|last4 = Lennon-Duménil|s2cid = 24791216}}</ref> Although the events taking place immediately after activation have yet to be completely determined, it is believed that B cells are activated in accordance with the kinetic segregation model {{Citation needed|reason = the mechanism of activation is actually quite controversial|date=April 2019}}, initially determined in T lymphocytes. This model denotes that before antigen stimulation, receptors diffuse through the membrane coming into contact with [[Lck]] and [[CD45]] in equal frequency, rendering a net equilibrium of phosphorylation and non-phosphorylation. It is only when the cell comes in contact with an antigen presenting cell that the larger CD45 is displaced due to the close distance between the two membranes. This allows for net phosphorylation of the BCR and the initiation of the signal transduction pathway{{Citation needed|date=April 2019}}. Of the three B cell subsets, FO B cells preferentially undergo T cell-dependent activation while MZ B cells and B1 B cells preferentially undergo T cell-independent activation.<ref name=":8">{{Cite journal|title = The generation of antibody-secreting plasma cells|journal = Nature Reviews Immunology|date = 2015-01-01|volume = 15|issue = 3|pages = 160–71|doi = 10.1038/nri3795|pmid = 25698678|first1 = Stephen L.|last1 = Nutt|first2 = Philip D.|last2 = Hodgkin|first3 = David M.|last3 = Tarlinton|first4 = Lynn M.|last4 = Corcoran|s2cid = 9769697}}</ref>
Η ενεργοποίηση των κυττάρων Β συμβαίνει στα [[δευτερογενή λεμφοειδή όργανα]] (SLOs), όπως στους [[σπλήνα]] και [[λεμφαδένες]].
B cell activation occurs in the [[secondary lymphoid organs]] (SLOs), such as the [[spleen]] and [[lymph nodes]].<ref name=":0" /> Αφού ωριμάσουν τα Β κύτταρα στο μυελό των οστών, μεταναστεύουν μέσω του αίματος σε SLOs, τα οποία λαμβάνουν σταθερή παροχή αντιγόνου μέσω της κυκλοφορίας [[λέμφου]].
After B cells mature in the bone marrow, they migrate through the blood to SLOs, which receive a constant supply of antigen through circulating [[lymph]].<ref>{{Cite journal|title = Early Events in B Cell Activation|journal = Annual Review of Immunology|date = 2010-01-01|pmid = 20192804|pages = 185–210|volume = 28|issue = 1|doi = 10.1146/annurev-immunol-030409-101216|first1 = Naomi E.|last1 = Harwood|first2 = Facundo D.|last2 = Batista}}</ref> Στο SLO, η ενεργοποίηση των Β κυττάρων ξεκινά όταν το Β κύτταρο συνδέεται με ένα αντιγόνο μέσω του BCR.
At the SLO, B cell activation begins when the B cell binds to an antigen via its BCR.<ref name=":7">{{Cite journal|title = How B cells capture, process and present antigens: a crucial role for cell polarity|journal = Nature Reviews Immunology|date = 2013-01-01|volume = 13|issue = 7|pages = 475–86|doi = 10.1038/nri3469|pmid = 23797063|first1 = Maria-Isabel|last1 = Yuseff|first2 = Paolo|last2 = Pierobon|first3 = Anne|last3 = Reversat|first4 = Ana-Maria|last4 = Lennon-Duménil|s2cid = 24791216}}</ref> Αν και τα γεγονότα που λαμβάνουν χώρα αμέσως μετά την ενεργοποίηση δεν έχουν ακόμη προσδιοριστεί πλήρως, πιστεύεται ότι τα Β κύτταρα ενεργοποιούνται σύμφωνα με το μοντέλο κινητικής διαχωρισμού, αρχικά προσδιορίστηκε σε Τ λεμφοκύτταρα. Αυτό το μοντέλο υποδηλώνει ότι πριν από τη διέγερση αντιγόνου, οι υποδοχείς διαχέονται μέσω της μεμβράνης που έρχονται σε επαφή με [[Lck]] και [[CD45]] σε ίση συχνότητα, καθιστώντας μια καθαρή ισορροπία φωσφορυλίωσης και μη φωσφορυλίωσης. Μόνο όταν το κύτταρο έρχεται σε επαφή με ένα κύτταρο που παρουσιάζει αντιγόνο, το μεγαλύτερο CD45 μετατοπίζεται λόγω της στενής απόστασης μεταξύ των δύο μεμβρανών. Αυτό επιτρέπει την καθαρή φωσφορυλίωση του BCR και την έναρξη της διαδρομής μεταφοράς σήματος. Από τα τρία υποσύνολα Β κυττάρων, τα κύτταρα FO Β κατά προτίμηση υποβάλλονται σε εξαρτώμενη από Τ κύτταρα ενεργοποίηση ενώ τα ΜΖ Β κύτταρα και τα Β1 κύτταρα κατά προτίμηση υπόκεινται σε ανεξάρτητη ενεργοποίηση Τ κυττάρων.
Although the events taking place immediately after activation have yet to be completely determined, it is believed that B cells are activated in accordance with the kinetic segregation model {{Citation needed|reason = the mechanism of activation is actually quite controversial|date=April 2019}}, initially determined in T lymphocytes. This model denotes that before antigen stimulation, receptors diffuse through the membrane coming into contact with [[Lck]] and [[CD45]] in equal frequency, rendering a net equilibrium of phosphorylation and non-phosphorylation. It is only when the cell comes in contact with an antigen presenting cell that the larger CD45 is displaced due to the close distance between the two membranes. This allows for net phosphorylation of the BCR and the initiation of the signal transduction pathway{{Citation needed|date=April 2019}}. Of the three B cell subsets, FO B cells preferentially undergo T cell-dependent activation while MZ B cells and B1 B cells preferentially undergo T cell-independent activation.
Αν και τα γεγονότα που λαμβάνουν χώρα αμέσως μετά την ενεργοποίηση δεν έχουν ακόμη προσδιοριστεί πλήρως, πιστεύεται ότι τα Β κύτταρα ενεργοποιούνται σύμφωνα με το μοντέλο κινητικής διαχωρισμού, αρχικά προσδιορίστηκε σε Τ λεμφοκύτταρα. Αυτό το μοντέλο υποδηλώνει ότι πριν από τη διέγερση αντιγόνου, οι υποδοχείς διαχέονται μέσω της μεμβράνης που έρχονται σε επαφή με [[Lck]] και [[CD45]] σε ίση συχνότητα, καθιστώντας μια καθαρή ισορροπία φωσφορυλίωσης και μη φωσφορυλίωσης. Μόνο όταν το κύτταρο έρχεται σε επαφή με ένα κύτταρο που παρουσιάζει αντιγόνο, το μεγαλύτερο CD45 μετατοπίζεται λόγω της στενής απόστασης μεταξύ των δύο μεμβρανών. Αυτό επιτρέπει την καθαρή φωσφορυλίωση του BCR και την έναρξη της διαδρομής μεταφοράς σήματος. Από τα τρία υποσύνολα Β κυττάρων, τα κύτταρα FO Β κατά προτίμηση υπόκεινται σε εξαρτώμενη από Τ κύτταρα ενεργοποίηση ενώ τα ΜΖ Β κύτταρα και τα Β1 κύτταρα κατά προτίμηση υπόκεινται σε ανεξάρτητη ενεργοποίηση Τ κυττάρων. <
B cell activation occurs in the [[secondary lymphoid organs]] (SLOs), such as the [[spleen]] and [[lymph nodes]].<ref name=":0" /> After B cells mature in the bone marrow, they migrate through the blood to SLOs, which receive a constant supply of antigen through circulating [[lymph]].<ref>{{Cite journal|title = Early Events in B Cell Activation|journal = Annual Review of Immunology|date = 2010-01-01|pmid = 20192804|pages = 185–210|volume = 28|issue = 1|doi = 10.1146/annurev-immunol-030409-101216|first1 = Naomi E.|last1 = Harwood|first2 = Facundo D.|last2 = Batista}}</ref> At the SLO, B cell activation begins when the B cell binds to an antigen via its BCR.<ref name=":7">{{Cite journal|title = How B cells capture, process and present antigens: a crucial role for cell polarity|journal = Nature Reviews Immunology|date = 2013-01-01|volume = 13|issue = 7|pages = 475–86|doi = 10.1038/nri3469|pmid = 23797063|first1 = Maria-Isabel|last1 = Yuseff|first2 = Paolo|last2 = Pierobon|first3 = Anne|last3 = Reversat|first4 = Ana-Maria|last4 = Lennon-Duménil|s2cid = 24791216}}</ref> Although the events taking place immediately after activation have yet to be completely determined, it is believed that B cells are activated in accordance with the kinetic segregation model {{Citation needed|reason = the mechanism of activation is actually quite controversial|date=April 2019}}, initially determined in T lymphocytes. This model denotes that before antigen stimulation, receptors diffuse through the membrane coming into contact with [[Lck]] and [[CD45]] in equal frequency, rendering a net equilibrium of phosphorylation and non-phosphorylation. It is only when the cell comes in contact with an antigen presenting cell that the larger CD45 is displaced due to the close distance between the two membranes. This allows for net phosphorylation of the BCR and the initiation of the signal transduction pathway{{Citation needed|date=April 2019}}. Of the three B cell subsets, FO B cells preferentially undergo T cell-dependent activation while MZ B cells and B1 B cells preferentially undergo T cell-independent activation.<ref name=":8">{{Cite journal|title = The generation of antibody-secreting plasma cells|journal = Nature Reviews Immunology|date = 2015-01-01|volume = 15|issue = 3|pages = 160–71|doi = 10.1038/nri3795|pmid = 25698678|first1 = Stephen L.|last1 = Nutt|first2 = Philip D.|last2 = Hodgkin|first3 = David M.|last3 = Tarlinton|first4 = Lynn M.|last4 = Corcoran|s2cid = 9769697}}</ref>
 
Η ενεργοποίηση των κυττάρων Β ενισχύεται μέσω της δραστηριότητας του [[Συμπληρωματικού υποδοχέα 2 | CD21]], ενός επιφανειακού υποδοχέα σε σύμπλοκο με επιφανειακές πρωτεΐνες [[CD19]] και [[CD81]] (και τα τρία είναι συλλογικά γνωστά ως σύμπλεγμα πυρήνων υποδοχέων Β κυττάρων ).
B cell activation is enhanced through the activity of [[Complement receptor 2|CD21]], a surface receptor in complex with surface proteins [[CD19]] and [[CD81]] (all three are collectively known as the B cell coreceptor complex).<ref>{{Cite journal|title = Human complement receptor 2 (CR2/CD21) as a receptor for DNA: Implications for its roles in the immune response and the pathogenesis of systemic lupus erythematosus (SLE)|journal = Molecular Immunology|date = 2013-01-01|pmc = 3439536|pmid = 22885687|pages = 99–110|volume = 53|issue = 1–2|doi = 10.1016/j.molimm.2012.07.002|first1 = Rengasamy|last1 = Asokan|first2 = Nirmal K.|last2 = Banda|first3 = Gerda|last3 = Szakonyi|first4 = Xiaojiang S.|last4 = Chen|first5 = V. Michael|last5 = Holers}}</ref> WhenΌταν aένα BCR bindsδεσμεύει anένα antigenαντιγόνο taggedεπισημασμένο withμε aένα fragmentθραύσμα ofτης theπρωτεΐνης συμπληρώματος C3, complementτο protein,CD21 CD21δεσμεύει bindsτο theθραύσμα C3 fragment, co-ligatesσυνδέεται withμε theτο boundδεσμευμένο BCR, andκαι signalsτα areσήματα transducedμεταφέρονται throughμέσω CD19 andκαι CD81 toγια lowerνα theμειώσουν activationτο thresholdκατώφλι ofενεργοποίησης theτου cellκυττάρου.<ref>{{Cite journal|title = Cell-specific regulation of the CD21 gene|journal = International Immunopharmacology|date = 2001-03-01|pages = 483–493|volume = 1|series = Unraveling Mechanisms and Discovering Novel Roles for Complement|issue = 3|doi = 10.1016/S1567-5769(00)00046-1|pmid = 11367532|first1 = Mark D.|last1 = Zabel|first2 = John H.|last2 = Weis}}</ref>
When a BCR binds an antigen tagged with a fragment of the C3 complement protein, CD21 binds the C3 fragment, co-ligates with the bound BCR, and signals are transduced through CD19 and CD81 to lower the activation threshold of the cell.<ref>{{Cite journal|title = Cell-specific regulation of the CD21 gene|journal = International Immunopharmacology|date = 2001-03-01|pages = 483–493|volume = 1|series = Unraveling Mechanisms and Discovering Novel Roles for Complement|issue = 3|doi = 10.1016/S1567-5769(00)00046-1|pmid = 11367532|first1 = Mark D.|last1 = Zabel|first2 = John H.|last2 = Weis}}</ref>
 
===T cell-dependent activation===
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