Nonspecific Immune System

[Ts1991]

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Quick question; though I should probably know this, I'm just getting a little confused. I know the adaptive immune branch responds to a certain set of antigens and recognizes "self" from foreign using MHC, but as for nonspecific I'm confused. If by defition the cells are "nonspecific", how are my nonspecific cells in my body not tearing me apart right now? In other words, I'm just asking how the nonspecific immune system "knows" what to respond to and what not to. Thanks in advance!

 

[MedPR]

Quick question; though I should probably know this, I'm just getting a little confused. I know the adaptive immune branch responds to a certain set of antigens and recognizes "self" from foreign using MHC, but as for nonspecific I'm confused. If by defition the cells are "nonspecific", how are my nonspecific cells in my body not tearing me apart right now? In other words, I'm just asking how the nonspecific immune system "knows" what to respond to and what not to. Thanks in advance!

Both non-specific and specific are able to recognize self cells. Non-specific "attacks" everything non-self whereas specific only "attacks" specific non-self things.

 

[Ts1991]

Thank you! But in order to recognize self cells, do they both use MHC?

 

[def1]

Quick question; though I should probably know this, I'm just getting a little confused. I know the adaptive immune branch responds to a certain set of antigens and recognizes "self" from foreign using MHC, but as for nonspecific I'm confused. If by defition the cells are "nonspecific", how are my nonspecific cells in my body not tearing me apart right now? In other words, I'm just asking how the nonspecific immune system "knows" what to respond to and what not to. Thanks in advance!

By non specific cells do you mean phagocytes and NK cells?

NK cells can detect nonspecific cells usually because they lack important self proteins. One example is that a virus can inhibit MHC class I on the surface and the NK cell can recognize the lack of MHC class I and kill the cell.

Macrophages detect complement on the surface of cells that have been opsonized. The cells are opsonized by antibodies or complement pathways are activated by lectins for mannose or by the alternative pathway. These complement don't bind to human cells due to proteins on our surface that inhibit complement pathways in certain ways.

Neutrophils work in a similar way as macrophages.

 

[MedPR]

Thank you! But in order to recognize self cells, do they both use MHC?

Yes. I don't remember the details, but I believe there is a difference between Ag presentation by MHCI vs MHCII.

 

[Ts1991]

Yea, I think you answered my question. So what my teacher refers to as "nonspecific immune cells" like: neutrophils, basophils, eosinophils, and macrophages mostly respond to a change in MHC? In class she mentioned that the "specific immune cells", as she called them, are able to identify self from non-self cells by recognizing our own MHC proteins. However, she said that only the "specific immune" cells such as B cells and T cells use this, which confused me as you can tell...

 

[def1]

Yea, I think you answered my question. So what my teacher refers to as "nonspecific immune cells" like: neutrophils, basophils, eosinophils, and macrophages mostly respond to a change in MHC? In class she mentioned that the "specific immune cells", as she called them, are able to identify self from non-self cells by recognizing our own MHC proteins. However, she said that only the "specific immune" cells such as B cells and T cells use this, which confused me as you can tell...

I'll try to summarize as best as I can

Innate Immunity: Do not use MHC directly

Phagocytes (neutrophils, macrophages, basophils, etc): These use complement receptors to bind cells that contain complement on their surface. C3 a complement protein, floats freely through the bloodstream binding to the surface of pathogen cells. It does not bind to human cells due to certain proteins that either cleave or inhibit the binding of this protein. Phagocytes also have receptors for antibodies, so when free floating antibodies bind to pathogens the phagocyte receptors bind them and destroy them.

NK Cells: These cells recognize when normal surface proteins are missing and destroy these cells.

Adaptive Immunity: Use MHC sometimes

T cells: These are the cells that use MHC. MHC presents peptides on the surface of human cells. T cell receptors bind to both the MHC and the peptide (MHC😛eptide complex) and are specific for only one MHC and one peptide. CD4 T cells bind to MHC class II. CD8 T Cells bind to MHC class I. Sometimes self proteins are presented on the MHC complex but these are negatively selected in the Thymus.

B Cells: These recognize epitopes on actual pathogen cells or toxins. However they must be activated by T cells through the MHC complex presented on the B Cell.

 

[Ts1991]

Ok thank you so much! I think I've got it now. It's probably much more effective to think of it as Innate or non-adaptive vs adaptive immunity. I over think things way too much...

 

[def1]

Ok thank you so much! I think I've got it now. It's probably much more effective to think of it as Innate or non-adaptive vs adaptive immunity. I over think things way too much...

Yea glad to help.

Not sure what you're studying for but The Immune System by Peter Parham is an amazing textbook for immunology.

Here is a link to a free book if you ever need help understanding something again, http://www.ncbi.nlm.nih.gov/books/NBK2394/