Lymphoid Tissues Flashcards
2 hallmarks of immunity?
Specificty and memory
What happens when a mature B cell binds to an antigen?
Somatic hypermutation- activation-induced cytidine (AID) makes random mutations in the antibody variable region memes. If the mutations cause the antibody to bind more strongly, this B cell will survive and may differentiate into antibody-producing plasma cells
What are primary organs?
Where lymphopoiesis occurs. e. thymus, bone marrow and fetal liver
Repertoire?
Range of genetically distinct BRCs and TRCs present a given host
What two cells do T-cell progenitors develop into?
T helper and T cytotoxic cells
What happens in the thymus?
Stepwise differentiation. Positive selection if T cell receptor can signal and then negative selection if T cell reacts against body
What declines with age?
Thymus output
Examples of secondary lymphoid tissues?
Spleen,lymph nodes, appendix and mucosal associated lymphoid tissue
3 facts about lymph nodes?
Highly organised, afferent and efferent lymphatic vessels and arterial and venous connections
Main role of spleen?
To filter blood
3 facts about epithelial barriers?
First line of defence against infection
Physical barrier
Extensive lymphatic network
Peyer’s patches?
Specialised secondary lymphoid tissues below the epithelium of the ileum. Have restricted follice sites where B cells undergo mutation and selection to generate high affinity antibodies
Tonsils?
High frequencies of follices and germinal centres, plus squamous epithelium for sampling foreign antigens
How do antigens get to lymphatic tissues?
Fluid drained between tissue cells is absorbed into the lymph
How often do naive T cells recirculate the body?
Every 24 hours
