Adaptive immunity Flashcards
HIV and adaptive immunity time-line:
- HIV infects CD4+ cells.
- CD4+ are depleted until they drop below threshold.
3.Disease progresses to AIDS.
Function of B lymphocyte.
Produces antibodies (humoral immunity).
10-15% of lymphocytes.
Triggered by antigen to differentiation into plamsa cells and memory B-cells.
Combat bacterial and some viral infection.
Function of T-lymphocyte
Cell mediated immunity.
75-80% of lymphocytes
Combats viruses, fungi, intracellular bacteria and cancerous cells.
What is immunological memory?
- Ability of the immune system to respond more rapidly and effectively to pathogens that have been encountered previously.
- Reflects clonal expansion lymphocytes with specificity for the antigen.
- Utilised in vaccination in which pathogen antigens are administered in a less harmful form, priming a response a response against the pathogen.
How does immunological memory lead to long lasting protection?
More responder cells available.
More efficient antigen recogntion/activation
Longer lasting
T cells produce more cytokines
B cells produce more antibodies
Where are lymphocytes present?
Specialised lymphoid tissues
MALT
Mucosal associated lymphoid tissue
What are the primary lymphoid organs
Bone marrow (B cell)
Thymus (T cell)
Function of primary lymphoid organs
Initial sites for lymphocyte production. This is where lymphocytes first express antigen receptors. Antigen independent differentiation
Whare the secondary lymphoid organs?
Lymph nodes, spleen and MALT.
What is the function of secondary lymphoid tissues?
Site where lymphocytes first encounter antigens.
Antigen dependent differentiation
What is a lymph node?
A secondary lymphoid tissue where resting B and T cells reside.
Function of lymph node
Filter lymph of cells like DC and foreign material.
B and T cells here first recognise and respond to antigen.
Antigen recognition drives antigen dependent differentiation.
Step by step of antigen independent maturation in the primary lymphoid tissues:
Occurs in bone marrow then thymus
Involves aquiring TCR
Positive and negative selection
T cell leave thymus, they now can respond to antigen
What migrates to the thymus in 8/9th week of human gestation?
Progenitor cells from site of haematopoiesis
Thymocyte
Developing T cell in thymus
How do T cells develop in the thymus
Thymocytes proliferate and differentiation into distinct sub populations of mature T cells. These mature T-cells migrate into secondary lymphoid tissues
Structure of the thymus
Lobular organ which is functionally seperated.
Where do immature thymocytes proliferate?
Outer layer of thymus cortex
Where do immature thymocytes undergo selection?
Thymus, inner cortex.
What is DiGeorge syndrome?
Developmental defect where the thymus doesn’t form. Have B cells but fewer T cells.
What makes a T-cell?
Expression of TCR
Why does T cell development involves rearrangement of the germline TCR genes?
Produce TCR proteins that recognise antigens.
What is positive selection of T cells?
Selection for T cells that have TCRs that bind to MHC molecules to be histocompatibile to the host.
