24/04/2023
Adaptive immune system (PY4010)
Adaptive immune system is…
Highly specific which means it can develop a memory for specific pathogens.
It recognises antigens which are molecules that initiate the adaptive immune response.
Each lymphocyte is genetically programmed to recognise one antigen, and once bound, the
lymphocyte proliferates rapidly. Once the antigen is eliminated, the adaptive immune
responses switch off.
Antigen recognition
Is the hallmark of the adaptive immune response.
B and T cells and antibodies recognise antigens.
2 molecules are involved in antigen recognition (T cell antigen receptors and
immunoglobulins, antibodies).
The cells recognise antigens presented on MHC molecules.
Antigens are presented by an antigen-presenting cell in an MHC complex. Antigen-
presenting cells include dendritic cells, macrophages, and B cells.
MHC Class I: presents products of protein synthesis made inside the cell. MHC Class II:
presents products which have entered the cell through digestion.
MHCI + antigen produces CD8 Cytotoxic T cells.
MHCII + antigen produces CD4 T helper cells.
T cells
T lymphocytes can interact with antigen-presenting cells by using their T cell receptor (TCR)
and a co-receptor (CD8 or CD4) to bind to the APC’s MHC molecule.
If a T lymphocyte recognises a specific antigen, it will proliferate and differentiate into
effector T lymphocytes of a particular type. Types of effector T lymphocytes include cytotoxic
T lymphocytes/killer T cells, helper T cells, and memory T cells.
Memory T cells are formed following an infection, and are antigen-specific and long-lived.
Memory T cells can quickly proliferate into large numbers of effector T cells upon reexposure
to the antigen and have a low activation threshold.
Memory T cells also provide the immune system with “memory” against previously
encountered antigens.
Helper T cells have TCR complexed with a CD4 molecule. When presented with an antigen
and MHCII, the TCR/CD4 complex binds to the antigen and MHCII with some other co-
stimulatory molecules and the helper T cell is activated.
Adaptive immune system (PY4010)
Adaptive immune system is…
Highly specific which means it can develop a memory for specific pathogens.
It recognises antigens which are molecules that initiate the adaptive immune response.
Each lymphocyte is genetically programmed to recognise one antigen, and once bound, the
lymphocyte proliferates rapidly. Once the antigen is eliminated, the adaptive immune
responses switch off.
Antigen recognition
Is the hallmark of the adaptive immune response.
B and T cells and antibodies recognise antigens.
2 molecules are involved in antigen recognition (T cell antigen receptors and
immunoglobulins, antibodies).
The cells recognise antigens presented on MHC molecules.
Antigens are presented by an antigen-presenting cell in an MHC complex. Antigen-
presenting cells include dendritic cells, macrophages, and B cells.
MHC Class I: presents products of protein synthesis made inside the cell. MHC Class II:
presents products which have entered the cell through digestion.
MHCI + antigen produces CD8 Cytotoxic T cells.
MHCII + antigen produces CD4 T helper cells.
T cells
T lymphocytes can interact with antigen-presenting cells by using their T cell receptor (TCR)
and a co-receptor (CD8 or CD4) to bind to the APC’s MHC molecule.
If a T lymphocyte recognises a specific antigen, it will proliferate and differentiate into
effector T lymphocytes of a particular type. Types of effector T lymphocytes include cytotoxic
T lymphocytes/killer T cells, helper T cells, and memory T cells.
Memory T cells are formed following an infection, and are antigen-specific and long-lived.
Memory T cells can quickly proliferate into large numbers of effector T cells upon reexposure
to the antigen and have a low activation threshold.
Memory T cells also provide the immune system with “memory” against previously
encountered antigens.
Helper T cells have TCR complexed with a CD4 molecule. When presented with an antigen
and MHCII, the TCR/CD4 complex binds to the antigen and MHCII with some other co-
stimulatory molecules and the helper T cell is activated.
