The Student Room Group

B and T cells help

Hi,
I am a little confused about the two types of lymphocytes.
Do B cells release antibodies without the binding to T cells? Do B cells have to be plasma cells in order to release antibodies? Are T cells stimulated to divide in the first place by B cells? Do B cells take in pathogens and present their antigens on the surface or is that just macrophages?
I think I have just confused myself at this point because the more I try to understand, the worse it gets.

Thank you
A level or GCSE?
A level
Okay,

"Do B cells release antibodies without the binding to T cells?"
For the purpose of A-level, no, naive B cells usually require 3 main signals to 'activate': (1) The binding of the antigen to the B-Cell Receptor (BCR)..... If a Helper T-cell also recognises that same antigen, then the T-cell will provide the other two required signals: (2) Co-stimulation signals from Helper T-Cells; e.g. binding of CD40L to CD40 on B-Cells, and (3) Soluble cytokine signals to direct the specific differentiation of the B-cell.

So B-cells require 'help' from Helper T-cells to functionally activate and start releasing antibody.

"Do B cells have to be plasma cells in order to release antibodies?"
Yes, plasma cells derive from activated B-cells with the purpose of antibody production. The other differentiated state is the 'surveillance'-like memory B-cells; whilst these dormant cells naturally circulate and will recognise antigens in future reinfections, they will quickly differentiate into plasma cells in order to produce antibodies upon stimulation.

"Are T cells stimulated to divide in the first place by B cells?" and "Do B cells take in pathogens and present their antigens on the surface or is that just macrophages?"
As with all science, things are constantly evolving and novel concepts are always arising. Classically, Helper T-cells are activated by Professional Antigen Presenting Cells (APCs) - typically dendritic cells and macrophages. Dendritic cells provide the 3 required signals: (1) Antigen in the context of MHCII, (2) Costimulation e.g. CD80/86 on APCs binding to CD28 on naive T-cells, and, (3) soluble cytokines directing which type of immune response to induce.

But the truth is most cells can present antigens in some capacity, but usually only in the context of MHCI which is only appropriate for activating cytotoxic T-cells, e.g. during viral infections. However, B-cells can also present in the context of MHCII (since they have to 'talk' with Helper T-cells) and are therefore technically Professional APCs... And there's some recent evidence indicating that under certain conditions they can present antigen and activate naive Helper T-cells:

https://onlinelibrary.wiley.com/doi/abs/10.1111/imr.12859

However, for the purpose of A-level, I'd stick with the classical teachings:
Dendritic Cells/Macrophages activate Helper T-cells, which in turn activate B-cells.


P.S Not sure if MHC is covered at A-level? If it's not, then dont worry about the difference between MHCI and MHCII, just refer to it as 'antigen presentation'.
Original post by HarisMalik98
Okay,

"Do B cells release antibodies without the binding to T cells?"
For the purpose of A-level, no, naive B cells usually require 3 main signals to 'activate': (1) The binding of the antigen to the B-Cell Receptor (BCR)..... If a Helper T-cell also recognises that same antigen, then the T-cell will provide the other two required signals: (2) Co-stimulation signals from Helper T-Cells; e.g. binding of CD40L to CD40 on B-Cells, and (3) Soluble cytokine signals to direct the specific differentiation of the B-cell.

So B-cells require 'help' from Helper T-cells to functionally activate and start releasing antibody.

"Do B cells have to be plasma cells in order to release antibodies?"
Yes, plasma cells derive from activated B-cells with the purpose of antibody production. The other differentiated state is the 'surveillance'-like memory B-cells; whilst these dormant cells naturally circulate and will recognise antigens in future reinfections, they will quickly differentiate into plasma cells in order to produce antibodies upon stimulation.

"Are T cells stimulated to divide in the first place by B cells?" and "Do B cells take in pathogens and present their antigens on the surface or is that just macrophages?"
As with all science, things are constantly evolving and novel concepts are always arising. Classically, Helper T-cells are activated by Professional Antigen Presenting Cells (APCs) - typically dendritic cells and macrophages. Dendritic cells provide the 3 required signals: (1) Antigen in the context of MHCII, (2) Costimulation e.g. CD80/86 on APCs binding to CD28 on naive T-cells, and, (3) soluble cytokines directing which type of immune response to induce.

But the truth is most cells can present antigens in some capacity, but usually only in the context of MHCI which is only appropriate for activating cytotoxic T-cells, e.g. during viral infections. However, B-cells can also present in the context of MHCII (since they have to 'talk' with Helper T-cells) and are therefore technically Professional APCs... And there's some recent evidence indicating that under certain conditions they can present antigen and activate naive Helper T-cells:

https://onlinelibrary.wiley.com/doi/abs/10.1111/imr.12859

However, for the purpose of A-level, I'd stick with the classical teachings:
Dendritic Cells/Macrophages activate Helper T-cells, which in turn activate B-cells.


P.S Not sure if MHC is covered at A-level? If it's not, then dont worry about the difference between MHCI and MHCII, just refer to it as 'antigen presentation'.

Thank you, this is so helpful.

Quick Reply

Latest

Trending

Trending