- #1
sameeralord
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MHC1 molecules are in all nucleated cells. MHC2 is in macrophages, does this mean they have no nucleus or they have one. Thanks 
Do Macrophages Have a Nucleus Based on MHC Molecule Presence?
- Thread starter sameeralord
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Discussion Overview
The discussion revolves around the presence of nuclei in macrophages in relation to MHC (Major Histocompatibility Complex) molecule expression, specifically MHC1 and MHC2. Participants explore the implications of these molecules on the cellular characteristics of macrophages and their role in the immune response.
Discussion Character
- Technical explanation
- Conceptual clarification
- Debate/contested
Main Points Raised
- One participant questions whether the presence of MHC2 in macrophages indicates they lack a nucleus, while others assert that macrophages do have a nucleus.
- Some participants note that macrophages can become multinucleated under certain conditions, such as during the formation of giant cells in immune responses.
- There is a discussion about the expression of MHC1 and MHC2 in relation to viral infection, with a participant suggesting that infected macrophages would express both markers.
- Another participant clarifies that MHC2 is expressed when presenting antigens from phagocytosed pathogens, while MHC1 is important for presenting internal antigens.
- Some participants emphasize that all nucleated cells, including macrophages, express MHC1, while only specific immune cells express MHC2.
- There is a mention of the role of MHC2 in eliciting responses from CD4 T-cells, including the requirement for CD40 as a coactivator.
- One participant discusses the relevance of MHC1 in monitoring internal antigens and the implications for unnucleated cells like platelets and red blood cells.
Areas of Agreement / Disagreement
Participants generally agree that macrophages are nucleated cells and express both MHC1 and MHC2, but there are differing views on the implications of these expressions and their roles in immune responses. The discussion remains unresolved regarding the specific relationship between MHC expression and the presence of a nucleus.
Contextual Notes
Some statements rely on assumptions about the definitions and roles of MHC molecules, and there are unresolved details regarding the mechanisms of antigen processing and presentation.
- #2
bobze
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yes they do
- #3
bobze
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In fact Big Macs can be multinucleated in some circumstances.
- #4
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As part of the immune response macrophages can form multinucleated giant cells.
- #5
sameeralord
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Thanks for the replies So that means if a macrophage becomes infected with a virus, it would show both MHC1 and MHC2 markers.
So that means if a macrophage becomes infected with a virus, it would show both MHC1 and MHC2 markers.- #6
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sameeralord said:Thanks for the replies
If I remember correctly MHCII is expressed when the cell in question presents the antigen of phagocytosed bacteria and other pathogens.
- #7
med17k
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Phagocytes are of course nucleated . The only unnucleated cells in Humans are Platelets and RBCs But what does this have to do with MHC 1 or MHC2?
- #8
bobze
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sameeralord said:Thanks for the replies
Almost all cells express MHCI. Except for those pointed out. There are other cells which also express low levels of MHCI like thyrocytes.
Remember that MHCI is important for expressing "self" or internal antigen and processing for that must go through the ER.
MCHII is expressed on professional antigen presenting cells like macrophages, dendritic cells, B-cells etc. This is for expressing external antigen and is processed through endosomes.
Also remember that MHCII is presented to CD4 T-cells and depending on their expression of cytokines elicits either a Th1 or Th2 type response (1 for cell mediated, 2 for antibody mediated). MHCII activation also requires CD40 as a coactivator to get that CD4 response.
- #9
bobze
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med17k said:
Because as a rule of thumb, people remember that MHC1 expression is to monitor internal antigen. Since unnucleated cells lack the cellular machinery for viral replication they aren't good targets for viruses. This means they don't really "need" MHCI to be monitored for cell-mediated immunity.
However, if you're something like Plasmodium this works out to your advantage.
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