B and T cells

[Ayyddaan]

Could someone please explain the mechanisms that allow interaction between B and T cells?? (INCLUDING MHC molecules?)

[Ayyddaan]

Direct yourselves to the bottom of the 'biology question thread' where this question was answered lol

[Sa1998]

can someone explain third line of defence pleassseeee

[studybuddy7777]

In case you are a fan of cheesy youtube videos - here is one here (dont lie you love them )

Otherwise direct yourself to the points I am about to discuss (please add to mine anyone if you want).The third line of defense will be shortened 3rd LoD because im too lazy to type it out ok?

-The 3rd LoD is specific unlike the other two.
-The third line of defence is activated when the pathogen has entered the body and surpassed the first two lines of defence. When a pathogen gets ingested by a phagocyte it displays its antigens on its surface.

-It consists of two stages: Cell Based Immunity and Humoral Immunity (i think this one is also called "antibody mediated immunity" in some texts)

Cell based immunity
Cell mediated immunity is a specific immune response that involves T lymphocytes that mediate an immune response not with antibodies, but rather with antigen-specific cytotoxic T cells and the release of cytokines. Along with humoral immunity, cell-mediated immunity forms part of the third line of defence. The two types of third line of defence mechanisms although considered to be separate entitires, interact during the immune response.
 
1. Macrophages reveal antigens to T Cells.
2. T cells with receptors are stimulated and divided resulting in more cells through the process of clonal expansion to produce cells with the same receptor.
3. These cells move to the infection area except for memory T cells
4. The cytotoxic T cells 'match' with the antigens and secrete cytokines that kill invading antigens
5. Helper T cells stimulate the Plasma B Cells (from the humoral response) to make antibodies.
6. Memory T cells remember the infection so further infections do not occur

EDIT: Oops forgot the humoral immunity! Notes are below

Humoral Immunity
The humoral response is a specific immune response that involves B lymphocytes recognizing antigens that are circulating in the blood or the lymph. Along with cell-mediated immunity, humoral immunity forms part of the third line of defence. The two types of third line of defence mechanisms although considered to be separate entities, interact during the immune response

Antibodies are key to this part of the 3rd LoD so a picture is attached below (Remember that each antibody responds/binds/engulfs a specific antigen)

This is just a brief outline on the third line of defense, but it is important you know this as examiners love to ask questions like this.

Hope I helped

[Skidous]

can someone explain third line of defence pleassseeee

For future reference, great seeing new people on the board btw, if you have any more questions try to direct them at the question thread that is stickied at the top of this board

Edit: Added link for easy reference.

[nibblez16]

Thank for the third line of defence explanations