Three Levels of Defence
Specific and Non-Specific Immunity
In non-specific immunity the same type and level of response occurs after exposure to a foreign antigen and there is no immunological memory of the antigen.
In specific immunity the response is specific to each antigen the immune system remembers prior contact and a greater response occurs if subsequent exposure to the same antigen occurs.
In specific immunity the response is specific to each antigen the immune system remembers prior contact and a greater response occurs if subsequent exposure to the same antigen occurs.
Self and Non-Self
Self cells carry the MHC markers that identify the cell as belonging in the body of the individual.
Non-self cells do not have markers that identify the cell as self but different surface antigens which are detected as being foreign and are therefore attacked by the immune system.
What is MHC?
MHC stands for Major Histocompatibility Complex and is a group of genes that code for the production of histocompatibility antigens on the external surface of all nucleated cells. These antigens are specific to the individual and identify all “self” cells.
Non-self cells do not have markers that identify the cell as self but different surface antigens which are detected as being foreign and are therefore attacked by the immune system.
What is MHC?
MHC stands for Major Histocompatibility Complex and is a group of genes that code for the production of histocompatibility antigens on the external surface of all nucleated cells. These antigens are specific to the individual and identify all “self” cells.
T Cells
T cells or T lymphocytes area type of lymphocyte that play a central role in cell-mediated immunity. There are several types of T cells, each with a unique function.
Macrophages
Macrophages are formed through the differentiation of monocytes which is one of the major groups of white blood cells of the immune system and are involved in non-specific immunity.
The function of macrophages is to protect the body from infection by engulfing invading pathogens at the site of infection or wound. Once the foreign substance is engulfed the vesicle containing the foreign substance will fuse with a lysosome and digest the bacterium. Waste substances will be expelled from the cell and antigenic fragments of the bacterium are combined with an MHC marker and displayed on the surface of the macrophage to alert other white blood cells of the invading pathogen.
The function of macrophages is to protect the body from infection by engulfing invading pathogens at the site of infection or wound. Once the foreign substance is engulfed the vesicle containing the foreign substance will fuse with a lysosome and digest the bacterium. Waste substances will be expelled from the cell and antigenic fragments of the bacterium are combined with an MHC marker and displayed on the surface of the macrophage to alert other white blood cells of the invading pathogen.
B Cells and Antibodies
Once a T helper cell is presented with an antigen by the macrophage the T helper cell then presents the antigen to immature B cells. The immature B cells then undergo colonial expansion to produce plasma B cells and several memory B cells. Plasma B cells produce antibodies that are specific to the antigen whilst memory B cells remain in the lymph in case of future reencounter.
Inflammatory Response
An inflammatory response occurs when the body sustains a wound that passes the first level of defence (skin) which allows pathogens to enter the body.