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Adapativr immunity

Adaptive immunity is specific for the particular foreign agent. If the host is re-exposed to the same agent, the response will be massively increased (memory).
Adaptive immunity is the ultimate immune response, where we adapt to change by producing new receptors that recognise antigens.
These receptors are found on T cells and B cells.


B cell receptors

Antibody molecules attached to the outside of the cells



The immune response must be capable of differentiating between self and non-self.
The ability to recognise self and not react is referred to as tolerance.



Antigens are referred to as compounds that are capable of provoking an immune response.
Most antigens are large and complex, and the individual components that are recognised by antibodies and T-cell receptors are referred to as epitopes


Primary lymphoid organs

Are those in which lymphocytes develop. The critical process is that T cells and B cells develop the new receptors associated with the adaptive immune response. They actually rearrange receptor genes in these primary lymphoid organs.


Secondary lymphoid organs

Are those in which naive T cells and B cells encounter their antigen and undergo proliferation. Cells that do not encounter their antigen are lost, because they die due to lack of stimulation


Development of lymphoid cells



Major histocompatibility complex (MHC)



Class 1 MHC



Antigen presenting cells (APCs)



Helper T lymphocytes

Central to the development of an immune response.

When vaccines are being produced we want to stimulate the appropriate subset of T cells in order to produce the most effective protective immune response


T helper 1

The T helper 1 subset of cells produces the cytokines gamma inferno, which stimulates macrophages and cytotoxic T cells


T helper 2

The T helper 2 subset of helper T cells is responsible for promoting allergic responses


Cytotoxic T lymphocytes

This type of T cell is important in killing infected cells, particularly host cells infected with viruses. They can also be involved in destruction of tumour cells.
Cytotoxic T cells destroy host cells by injecting cytotoxic molecules that result in host cell death


B lymphocytes

B lymphocytes recognise antigens and change to become antibody secreting plasma cells.
The antibody made by the plasma cell will recognise the antigen that the B cell originally recognised.
Immunity associated with antibodies is often called HUMORAL IMMUNITY


Antibodies(or immunoglobulins)

The terms antibody and immunoglobulin are synonymous.
Antibodies are produced by activated B cells (plasma cells).
Antibodies are Y-shaped molecules that recognise antigens


Antibody isotypes

Antibodies recognise antigens. There are 5 different classes (or isotypes) of antibodies:

IgG, IgM, IgA, IgE and IgD.



Lymphocytes circulation

Both T cells and B cells, as well as a range of other cells, are constantly circulating throughout our bodies. We can think of the blood vessels as the highways and the rest of the body as the suburbs. Taking a sample of blood from the blood vessels is a small subset of those cells that are in transit. This constant circulation of cells provides massive opportunities for both T cells and B cells to encounter antigens where ever they are occurring.