Few questions about immunology

[scilearner]

1. Why can't antibodies enter virus infected cells. Why can't virus infected cells make their membrane permeable for antibodies.

 

2. Why doesn't the body create antibodies against self. What is the mechanism behind the body knowing which cells are self and non self.

 

3.How do memory cells increase the response second time. Do the antigens get bind to memory cells quicker and then the process activates faster.

 

4. How are white blood cells produced in lymph?

 

Thank you!!

[GDG]

1. Why can't antibodies enter virus infected cells. Why can't virus infected cells make their membrane permeable for antibodies.

 

2. Why doesn't the body create antibodies against self. What is the mechanism behind the body knowing which cells are self and non self.

 

3.How do memory cells increase the response second time. Do the antigens get bind to memory cells quicker and then the process activates faster.

 

4. How are white blood cells produced in lymph?

 

Thank you!!

 

1. Antibodies are fairly large proteins, and are not typically internalized by cells (although this does occur in certain disorders). Why can't cells make their membranes permeable? Making the membrane permeable enough for antibodies would probably be enough to kill the cell (after all, this is how complement kills cells): most large proteins that are internalized are taken in by specific mechanisms. Typically, the virus-infected cell may no longer be in control of its "operating machinery", because it has been hijacked by the virus, so defenses that require the cell to change somehow would be subject to failure.

 

2. This is not perfectly understood, but is thought to be regulated by T cells. B cells (which produce antibodies) need activation by T cells in the context of the antigen. When T cells are maturing, T cells that react strongly to "self" antigens are weeded out, thus eliminating the T cells that would activate B cells to make "self" Abs. When this fails, you can get autoimmune diseases, like lupus.

 

3. It can take a few weeks, from first exposure to an antigen to effectively fighting it off. Much of this time is spent "selecting" the best Abs and T cells, and then further refining them.* Then, the selected immune cells need to divide again and again in order to build up a sufficient population to challenge the invading pathogens. In contrast, the memory cells represent immune cells that are already optimized, and ready to crank out plasma cells and Tc cells immediately.

 

*When I say "select", this just means that cells that produce Abs that bind well are stimulated to divide, while those that don't aren't.

 

4. White blood cells (lymphocytes) are produced mainly in the bone marrow. They differentiate from stem cells called hematopoietic stem cells. See Hematopoiesis.

[scilearner]

1. Antibodies are fairly large proteins, and are not typically internalized by cells (although this does occur in certain disorders). Why can't cells make their membranes permeable? Making the membrane permeable enough for antibodies would probably be enough to kill the cell (after all, this is how complement kills cells): most large proteins that are internalized are taken in by specific mechanisms. Typically, the virus-infected cell may no longer be in control of its "operating machinery", because it has been hijacked by the virus, so defenses that require the cell to change somehow would be subject to failure.

 

2. This is not perfectly understood, but is thought to be regulated by T cells. B cells (which produce antibodies) need activation by T cells in the context of the antigen. When T cells are maturing, T cells that react strongly to "self" antigens are weeded out, thus eliminating the T cells that would activate B cells to make "self" Abs. When this fails, you can get autoimmune diseases, like lupus.

 

3. It can take a few weeks, from first exposure to an antigen to effectively fighting it off. Much of this time is spent "selecting" the best Abs and T cells, and then further refining them.* Then, the selected immune cells need to divide again and again in order to build up a sufficient population to challenge the invading pathogens. In contrast, the memory cells represent immune cells that are already optimized, and ready to crank out plasma cells and Tc cells immediately.

 

*When I say "select", this just means that cells that produce Abs that bind well are stimulated to divide, while those that don't aren't.

 

4. White blood cells (lymphocytes) are produced mainly in the bone marrow. They differentiate from stem cells called hematopoietic stem cells. See Hematopoiesis.

 

Thanks a lot Only now I realized that I have asked some very difficult questions. Thanks for the help