BLD434 Section 1 Flashcards
Immunology
Antigen
pathogen component that binds to BCR or TCR
Innate Immunity
First line of defense (Non-specific) - Inflammation
- rapid pathogen recognition response (hours)
- fixed - based on the inherited receptors
- limited # of specificities
- constant during response
- neutrophils, eosinophils, basophils, mast cells, monocytes (B)/phagocytes (T), DC, NK cells, ILC
Adaptive Immunity
Third line of defense. Antigen-specific
- Slow pathogen recognition response
- Variable (not based on inherited genes)
- Numerous highly selective specificities
- Improves during response and each time infected
- B cells (plasma cells, CD19 and CD20), B-1 forms before birth, B-2 forms after birth
- T cells (CD3) - Helper T cells & T regulatory cells (CD4), Cytotoxic T cells (CD8)
Main advantages: more powerful & long-lasting protection (memory)
CD antigen (marker)
“clusters of differentiation” - cell surface molecules that identify immune cells
Sebum
Substance secreted by sebaceous glands that contains fatty acids and lactic acids which inhibit bacterial growth at the skin surface.
Lysozyme
Enzyme contained in tears and saliva that kills bacteria by degrading their cell walls.
Polymorphonuclear
having a nucleus with several lobes and a cytoplasm that contains granules (ex: neutrophils, eosinophils, basophils)
Primary lymphoid tissue
Bone marrow - where B & T cells form and multiply. where B cells mature.
Thymus - where T cells mature.
Secondary lymphoid tissue
Filters extracellular fluids for antigens and microorganisms. Site for lymphocyte activation by antigens, which develop into effector cells.
- Lymph nodes, spleen, tonsils, Peyer’s patches , appendix.
Lymph
fluid and cells (including WBCs) that are transported to the lymphatics and into the bloodstream
- Attack bacteria in the blood and body tissues
Naive lymphocyte
Immature B or T lymphocytes that have not been activated by an antigen
PALS (Periarteriolar lymphoid sheath)
A portion of white pulp in the spleen that is occupied by T cells.
GALT (Gut-associated lymphoid tissue)
Tonsils, adenoids, appendix, Peyer’s patches of the gastrointestinal tract
BALT (Bronchial-associated lymphoid tissue)
aggregates of the respiratory epithelium
- mucosal lymphoid tissue in the walls of airways (respiratory tract, bronchi)
MALT (Mucosa-associated lymphoid tissue)
Secondary lymphoid tissue that initiates immune responses to specific antigens along mucosal surfaces (ex: vaginal tract)
Mature immune cells from the common Myeloid precursor
Monocytes/Macrophages, Neutrophils, Eosinophils, Basophils, Mast cells, DC cells
Mature immune cells from the common Lymphoid precursor
B cells, T cells, NK cells, ILC (innate lymphoid cells)
Monocytes vs Macrophages
Same cell but is called a monocyte (inactive) when in the blood and a macrophage (active) when in tissue. Macrophages are phagocytic while monocytes are not
Polymorphonuclear leukocytes (granulocytes) of the blood - color of granules & # of lobes
Neutrophils (2-5 lobes) - pink/blue/lilac
Eosinophils (2 lobes) - orange-pink
Basophils (2 lobes) - purple-black
How does a naive lymphocytes enter a lymph node?
Naïve lymphocyte enters a lymph node via afferent lymphatic vessels and drains through the efferent lymphatic vessel in the medulla
M cell (Microfold cell)
Specialized intestinal epithelial cells covering GALT mucosa – Transport antigens to lymphoid follicles to initiate an immune response. Long-lived.
How does an antigen enter a lymph node?
Antigen enters lymph node via fluid draining from tissues (due to inflammation) in afferent lymph vessels
Where are B & T lymphocytes primarily located in the lymph node?
B cell - Lymphoid follicles in the cortex (circular areas in the outer part)
T cell - Medulla (middle part)/ T-cell area
Where are B & T lymphocytes primarily located in the white pulp of the spleen?
Active B cell - Germinal center
Inactive B cell - lymphoid follicles
T cell - PALS (periarteriolar lymphoid sheath)
C (Complement proteins)
soluble zymogens (inactive enzymes) in the blood that are part of the innate immune system
First line of defense against infection
Defensins
small amphipathic proteins inserted into pathogenic membranes to cause lysis. Defend against bacterial, viral, and fungal infections
Opsonization
Coating or binds to the surface of a pathogen to help phagocytosis.
Complement fixation
Opsonization where C3b is the opsonin.
- C3b is covalently bonded to the pathogen’s surface to mark it as a target for destruction by a phagocyte
Anaphylatoxin
Complement fragments that float away (C3a, C4a, C2b)
- Substance that activates blood vessel endothelial cells to initiate inflammation by: causing degranulation, increasing vascular permeability and vasodilation.
Chemoattractant
A chemical substance that creates a gradient to attract cells (from low to high concentration) towards an infection
4 Main Functions of complement proteins in immune system
- opsonization
- anaphylatoxin
- chemoattraction
- direct lysis (pore formation - C9)
List the 3 Complement Pathways and what initiates them
- Classical (Antibody-initiated, C1 binds)
- CRP initiates without antigen binding
- Lectin (MBL binds)
- Alternative (spontaneous hydrolysis of C3, Factor B binds)
C3 covertase (Classical and Lectin)
C4b2a
C3 convertase (Alternative)
C3bBb