Nansi
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In the immune response you have B cells and T cells. In what cases are B cells used and in what cases are T cells used? Why do we need T cells if we have B cells which produce antibodies and make the bacteria easier to locate for macrophages ? The whole idea confuses me and I haven't been able to find a flow diagram or anything to explain it. Any help is appreciated tbh
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KSaRa
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So in the immune response, you have 2 responses - the humoral response and the cell-mediated response.

The humoral response is further divided into 2 stages - the T-helper activation stage and the Effector stage
1. T-helper activation stage - A macrophage engulfs a pathogen and its antigens are processed. The antigens then form a complex with the Major Histocompatibility Complex to form an Antigen/MHC complex which is presented on the surface of the macrophage (antigen presenting cell). The CD4 receptors on a T-helper cell bind to this complex and the T-helper cell is then activated. This activated T-helper cell clones to form T-memory cells and active T-helper cells.
2. Effector stage - A B-cell binds to the antigens on a pathogen and the B-cell becomes an antigen presenting cell by forming an antigen/MHC complex. Then, the activated T-helper cell from the previous stage releases chemicals which then activate this antigen presenting B-cell. The B-cell then clones into B-memory cells and B-effector cells. The B-effector cells undergo differentiation to form plasma cells. The plasma cells then release antigen-specific antibodies in large numbers.

I hope this answers your questions, and do let me know if you need any help with the cell-mediated response which involves T-killer cells.
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ctchannah
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First of all the theres 2 types of T cells that activate the immune response of the surface of the antigen on the pathogen
T HELPER CELLS- activate B cells and cytotoxic t cells
T Cytotoxic cells- kill the pathogen

Once the B cells are activated they all have their own specific antibody, the complementary b cell will form an antigen-antibody complex to the antigen then will form plasma cells then memory cells blablabla

cba with the rest lol
(Original post by Nansi)
In the immune response you have B cells and T cells. In what cases are B cells used and in what cases are T cells used? Why do we need T cells if we have B cells which produce antibodies and make the bacteria easier to locate for macrophages ? The whole idea confuses me and I haven't been able to find a flow diagram or anything to explain it. Any help is appreciated tbh
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Jpw1097
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(Original post by Nansi)
In the immune response you have B cells and T cells. In what cases are B cells used and in what cases are T cells used? Why do we need T cells if we have B cells which produce antibodies and make the bacteria easier to locate for macrophages ? The whole idea confuses me and I haven't been able to find a flow diagram or anything to explain it. Any help is appreciated tbh
B cells produce antibody and are therefore effective against extracellular pathogens (e.g. extracellular bacteria, viruses before they enter cells). Antibodies can bind to pathogens and neutralise them (i.e. stop them entering our cells), opsonise them (the Fc portion of the antibody can bind to receptors on phagocytes, allowing the pathogen to be phagocytosed), activate complement (complement proteins bind to the pathogen and can also opsonise the pathogen or even lead to the formation of the membrane attack complex - essentially it forms a pore in the pathogens wall, causing the pathogen to lyse).

As for T cells, there are two main types of T cells: cytotoxic or killer T cells - which kill cells that have been infected by a pathogen, and helper T cells - of which there are many types that activate B cells, activate phagocytes, suppress autoreactive T cells, etc.
T cells are particularly important for intracellular pathogens - that is, pathogens that are inside our own cells. Infected cells present part of the antigen on their surface on MHC I molecules. Cytotoxic T cells that recognise this antigen will then kill the infected cell. Professional antigen presenting cells (e.g. macrophages) which have phagocytosed a pathogen will present a part of the antigen on their surface using MHC II molecules - helper T cells which recognise this antigen then become activated and may activate B cells, recruit more phagocytes to the area, or they increase the ability of infected cells to kill the intracellular pathogens.
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