Lecture 2 (Week 1B) - Lymphocyte Formation Flashcards
The cells of the immune system work as
an INTEGRATED DEFENSE system to eliminate or control an infectious agent
The immune system provides
LONG-LASTING PROTECTIVE IMMUNITY
Pathogens target various
compartments of the body
which require different host defense mechanisms for eradication
Extracellular host defense mechanisms
blood, lymph, interstitial spaces
• antibodies
• complement
• phagocytosis
epithelial surfaces
• antibodies (IgA)
• antimicrobial peptides
Antibodies abbreviation
IgA
Ab
Intracellular host defense mechanisms
cytoplasmic
• cytoxic T cells
• NK cells
vesicular
• T cell-dependent macrophage activation
Immunogen
anything which elicits an immune response
Antigen
anything recognized by a
• B cell receptor (antibody or
• T cell receptor
An antigen is a part
of something which our bodes may encounter • bacteria • virus • fungi • parasite • food protein • pollen etc
All immunogens are
all immunogens are antigens
BUT
all antigens are not immunogens
Hapten
injected into an animal = no immune response
eg DNP
A hapten is
a hapten is a antigen, but it is NOT an immunogen
Protein carrier
injected into animal = anti-BSA Ab
eg BSA
Hapten-carrier
congugate injected into animal =
anti-BSA Ab
anti-DNP Ab
eg DNP-BSA
Epitopes
immunologicallly active parts of an antigen
Antibodies (Abs) can bind to
epitopes on antigens
The lymphoid system
- primary lymphoid tissue
* secondary lymphoid tissue
Primary lymphoid tissue
where lymphocytes are made
• Thymus - T cells
• Bone marrow - B cells and NK cells
B of B cell
is for Bursa (the primary lymphoid tissue for B cells in birds)
• NOT FOR BONE-MARROW
Bursa
the primary lymphoid tissue for B cells in birds
Secondary lymphoid tissue
where immune responses occur • lymph nodes • spleen • tonsils • Peyer's patches (gut) • appendix
Primary lymphoid tissue size
size is antigen-independent
Secondary lymphoid tissue size
size is antigen-dependent
eg secondary lymphoid tissue in the gut
Lymphatic vessels
allow fluid to drain from the tissues into lymph nodes
• the lymphatic system is designed to get antigens into lymph nodes, where the antigens can stimlate T cells and B cells
- “draining lymph node”
- afferent lymphatic vessel
The lymphatic system is designed to
get antigens into lymph nodes, where the antigens can stimulate T cells and B cells
• “draining lymph node”
• afferent lymphatic vessel
T and B cells reside in
different parts of the lymph nodes
• T cells = paracortex
• b cells
• germinal center
High Endothelial Venule (HEV)
HEVs are specialized post-capillary venous swellings that allow circulating lymphocytes to leave the blood and enter the lymph nodes
The spleen is the lymphoid tissue which
samples antigens in the blood
• splenectomised individuals are more susceptible to blood infections = septicaemia
Splenectomised individuals are more susceptible to blood infections = septicaemia
blood infections = septicaemia
Splenic structure
white pulp
• primary follicle
• marginal zone
• periarteriolar lymphoid sheath (PALS)
artery and vein
In mammals, B cells develop from
stem cells in the bone marrow • stem cells --> • Pro-B cells --> • Pre-B cells --> • immature B cells (--> mature naive B cells)
B cells become
plasma cells which produce huge amounts of diverse antibodies
Plasma cells produce
huge amounts of diverse antibodies
T cells recognize antigens using their
T Cell Receptor (TCR)
• αβ TCR
- TCRβ
-TCRα
• γδ TCR
- TCRγ
- TCRδ
T cells are generated in
the thymus
a primary lymphoid tissue
Thymus structure
cortex (outside)
medulla (inner part)
The thymic gland … with …
involutes with age
All T cells develop from
a common bone marrow-derived progenitor in the thymus
After eg a serious cut, dendritic cells to go
the draining lymph nodes
