Antigen presentation (a key process in the initiation of the adaptive immune system, involved the selection of a T helper cell (type of T lymphocyte))

1.

APCs engulf and digest pathogens via phagocytosis, displaying pathogenic antigens on their MHC Class 2 markers

2.

they then travel via the lymphatic system to lymph nodes to present foreign antigens on their surface using their MHC Class 2 proteins, which interact with complementary T cell receptors on the surface of specific T helper cells

3. 
   

1. when this interaction occurs, the T helper cell becomes activated and is said to be ‘selected’, and can then help initiate the adaptive immune response through humoral or cell-mediated immune responses

Third Line of Defence (adaptive immune system)

signed to combat pathogens that have breached the first line of defence

initiated by the presentation of non-self antigens to specific immune cells of the adaptive immune system

unlike the second line of defence, it;

• is specific (responds to each distinct pathogen in a unique and tailored way

• has immunological memory (produces cells that allow the body to respond to future re-infections by a previously encountered pathogen quickly and effectively