Confused about how B cells work.

[APPLEhead]

I know that Th cells stimulate B cells to proliferate, and then differentiate into plasma cells and B memory cells, but it's the binding that confuses me. I always thought that the Th cell would bind to the MHC marker 2 of a macrophage or dendritic cell, and this will cause the Th cell to release interleukin which stimulates B cells and so on. But in the Neap answers, it says that B cells have receptors that bind to the antigen fragments, and this is what causes the B cell to proliferate.

:s

Also, which type of lymphocytes, T or B, is responsible for organ/tissue rejection?

Thanks in advance to anyone who can help.

[ligands]

T cytotoxic cells are responsible for tissue rejection

The th cell simply binds to the mhc class 2 marker and stimulates b cells to bind to the antigen and if it's specific enough it will proliferate, you can find a diagram of this process on google or in a text book

[spherelin]

Not really sure about NEAP's answers, but i had the same problem as you, i asked my teacher and she said that B cells only replicate into plasma cells and b memory cells via interleukin 1 secreted from T helper cells... :/

[ligands]

All b cells that have no proliferated/differentiated will have antibodies on it's membrane to bind to the antigen and this is what is going to replicated on all memory and plasma cells and what will produced by plasma cells

[spherelin]

wait so does this mean that B cells can start 3rd line of defence without T helper cell stimulation?

[ligands]

Don't think so, I think they need to be stimulated but that antibody on the outside is what the th cell uses to recognizes the most specific match to a antigen

[InsaneMcFries]

B cells CAN divide without T helper cell stimulation, but it is very limited and is nowhere near efficient enough to cope with a pathogen that is wide spread.

Also, it is interleukin-2 that Th cells secrete, macrophages secrete interleukin-1 when there is a fairly high amount of non-self molecules in an area.

But yeah, as B cells are antigen-presenting cells, they can bring the antigen to the Th cells as well.