Lymphatic System Flashcards
What are the two parts of the immune system?
Innate Immunity
Adaptive Immunity
Does the innate system respond first or second? What types of cells are a part of innate immunity? What does it do?
1st responder
Basophiles, esosinophiles, neutrophiles, macrophages
Phagocytosis, complement, inflammation
Does the adaptive system respond first or second? What types of cells are a part of adaptive immunity? What does it do?
2nd Response
B cells, T cells, NK cells
Target the specific pathogen
What is a humoral response? Which cells are acting? Is the response concentrated? Is it part of innate or adaptive immunity?
B cells secrete antibodies
Antibodies can travel to distant locations
Part of the adaptive immunity
What is a cell-mediated response? Which cells are acting? Is the response concentrated? Is it part of innate or adaptive immunity?
T cells, specifically CD4+ and CD8+
Requires direct contact
Part of the adaptive immunity
What is an antigen?
something that induces an immune response
any ligand recognized by B and T cells
What are the two fates of a B cell after activation?
- Plasma Cell - pump antibodies
2. Memory Cell
What are the 5 isotypes of antibodies? What are their functions?
- IgM - Primary response
- IgG - Secondary response
- IgA - Body Secretions
- IgE - Parasitic infections, allergies, hypersensitivities
- IgD - unknown
What is class switching?
Antibodies start as IgM and can then class switch to IgG, IgA, IgE by changing the heavy chain of the BCR
What are the five functions humoral immunity does to help defeat the pathogen?
- Neutralization
- Opsonization
- Oxidation
- Agglutination
- Antibody-dependent cellular cytotoxicity (ADCC)
What is neutralization? How does it work?
Antibodies bind to the pathogen and neutralize it
Two methods:
1. Prevents toxins ability to act
2. Block attachment site = can’t enter into host cells
What is opsonization?
The antibodies coat the pathogen making it easier for the pathogen to by phagocytosed
What is oxidation? (In regards to humoral immunity)
Antibodies activate ROS production, the build-up of ROS kills the pathogen
What is agglutination? When does it occur?
Antibodies and the foreign cells clump together to form an immune complex
Occurs during miss-match blood transfusions
What is the process of Cell-Mediated immunity?
Antigen-presenting cell (usually a dendritic cell) presents the antigen to the T-cell > T cell become activated > differentiation > proliferation
What are the two fates of an activated T cell?
- Memory
2. Join the effector pool (Th, Tfh, Tc, etc)
What is an epitope?
Part of the pathogen that can be bound to
It can be processed and presented by antigen-presenting cells
What causes swollen lymph nodes during times of infection?
T cells recognize antigen in secondary lymphatic leading to massive proliferation and differentiation
What is a lymph node? What shape does it have? What is its function?
Kidney shaped thing part of the immune system
Filter lymph, cite of development for T and B cells
What about the vasculature of the lymph nodes aids it in filtering the lymph?
There are multiple afferent tubules, but only one efferent tubule
This creates a bottleneck, cause the lymph to move through more slowly
What does the CD8+ T cell do once it is activated?
CD8+ T cell checks cells > recognized antigen and MHC > releases porfin > creates a pore in the cell > releases granzymes into the pore > death of the infected cell
What is lymph (2)?
- Excess interstitial fluid
2. large, foreign debris
What is the thymus? Where is it located? Does B or T cell maturation happen here?
Primary Lymphatic organ
Above the heart
T cell maturation (T - Thymus)
Where does hematopoiesis occur?
In the bone marrow
What three regions of the body do lymph nodes concentrate around?
- Groin
- Axillary
- Cervical Region
What is the main function of the spleen?
Removes aged and dying RBC
What is the main function of tonsils?
Form ring of protection around the oral pharynx
What does the diffuse lymphatic tissue consist of?
- MALT (GALT and BALT)
2. Lymphatic nodules
What is MALT?
Mucosa-associated lymphoid tissue
Immune cells in the lamina propria
What are lymphatic nodules?
Unencapsulated aggregates of immune cells
Which of the following lymphoid organs are primary? Secondary? Lymph nodes Spleen Tonsils Thymus Bone Marrow
Primary: thymus, bone marrow
Secondary: lymph nodes, spleen, tonsils
Where does B cell development take place?
In the bone marrow
What are the characteristics of diffuse lymphatic tissue? What is its function?
Not enclosed by a capsule
Enriched in alimentary canal, respiratory passages, and genitourinary tract
Site of initial immune response
What types of cells are enriched in MALT?
Lymphocytes, Eosinophils, Mast cells, Macrophages
What are the two major features of lymphatic nodules?
- Germinal Center
2. Corona
What occurs in the germinal centers of lymphatic nodules? How does it stain? Why?
Site of lymphocyte activation and clonal expansion
Stains lighter due to cells increasing in size and thus having more cytoplasm
What occurs in the corona of lymphatic nodules? How does it stain? Why?
Site of small lymphocytes (storage)
Stains more densely due to packed lymphocytes
What are the three tonsils? Where are they located?
- Lingual tonsils: posterior 1/3 of the tongue
- Pharyngeal tonsils: nasal cavity
- Palatine tonsils: sides of the throat
What cell type composed the palatine tonsils?
Stratified Squamous
LCT directly below epithelium - not always clearly visible
What are tonsillar crypts? What is their function?
Crevices in tonsils
Important for catching food/particles/debris in order to bring them into proximity with immune cells
What is the hilum region of lymph nodes?
Place where efferent lymph vessels leave and entry/exit for arteries and veins
The sinuses create a meshwork of ________ which is very important for filtration through the lymph nodes
Reticular Fibers
What is the order that lymph flows through the lymph node? (include the 3 different sinus types)
- Subcapsular Sinus
- Trabecular Sinuses
- Cortex
- Paracortex
- Medullary Sinuses
- Efferent exit
What type of tissue is the capsule of the lymph node made of? What does it surround?
DCT
Surrounds node
What type of tissue are the trabeculae of the lymph node made of? What does it form? What does it deliver?
DCT
Forms framework
Delivers blood vessels and nerves
What does reticular tissue form in the lymph node? What are its two functions?
Reticular tissue = reticular cells, reticular fibers (Type III collagen)
- filters lymph
- Attracts T cells, B cells, and dendritic cells AND acts as an attachment point
What is the primary site of B cell germination?
the cortex of the lymph nodes
What is the primary site of T cells?
paracortex (deep cortex) of the lymph nodes
What are HEVs? Where are they located?
HEV = High Endothelial Venuels - entrance point for 90% of lymphocytes
Located in the para/deep cortex
What can be found in the medulla of the lymph nodes?
Irregular lymphatic/medullary chords separated by medullary sinuses
What are medullary chords? Medullary sinuses?
Medullary chords = reticular fibers with macrophages, dendritic cells, and B cells attached
Medullary sinuses = in between the medullary chords, where the lymph drains
What tissue type do you find around the HEV?
Simple cuboidal / simple columnar
Absorb large amounts of fluid
What do AQ1 do for HEVs?
Facilitate absorption of fluid from lymph
What two processes do T cells undergo in the thymus?
- Positive selection - is it functional?
2. Negative selection - does it respond to self?
When is the thymus most active? How does it change in size throughout your life?
Most active shortly after birth
Involutes (gets smaller?) once you hit puberty and is replaced with adipose tissue
What are the four structures that make up the thymus?
- Capsule - thin CT
- Trabeculae - CT
- Cortex
- Medulla
What does each lobule of the thymus have? (2)
- Cortex
2. Medulla
What cell types are in the cortex of the thymus? How does it stain?
Outer region
Small thymocytes
Stains dark because of small amount of cytoplasm
What cell type is in the medulla of the thymus? what other structure can you find there? how does it stain?
Inner region
Large thymocytes
Thymic (Hassall’s) Corpuscle
Stains lighter because larger cytoplasm
What do Hassall’s / thymic corpuscles look like? Where are they located? What is their function?
Large pink structures
Located in the medulla of the thymus
Produce cytokines
What is the function of the blood-thymus barrier?
Protects developing lymphocytes from exposure to antigens
Don’t want premature exposure
What are the three layers to the blood-thymus barrier?
- Capillary epithelium - continuous with tight junctions reinforced by pericytes
- Perivascular CT with macrophages (engulf anything that might get through)
- Epithelioreticular Cells - create a wall that surrounds CT
What is thymic education?
T cells come from the BM > enter the thymus through post-capillary venules in medulla > traffic upwards to cortex > positive selection (presented by type II epithelial cells = dendritic cells) > pass positive selection = pass-through type III and IV epithelial cells > medulla > negative selection (presented self-antigen by V epithelial cells) > pass neg selection = exit and traffic to the site of infection
What happens if the T cell fails positive selection?
Apoptosis
What happens if the T cell fails negative selection?
Apoptosis
What do type VI epithelial cells form in the thymus?
Form a lamellar structure that gives an eosinophil stain
What would be the outcome if negative selection fails?
Autoimmune disease
What are the two functions of the spleen?
- Filters Blood
2. Performs Immune Functions
What are the two things the spleen removes from the blood? Where does the blood enter from?
Senescent (dying) RBC
Microbes
Splenic artery
What two immune functions does the spleen serve?
- Antigen presentation by APCs
2. Production of antibodies
The spleen in enclosed by a __________ and trabeculaie containing ________
Dense CT capsule
Myofibroblasts
What is the function of myofibroblasts in the spleen?
Have the potential to contract to cause the spleen to act like a sponge and expel all the blood out
What are the two regions of the spleen?
Red Pulp Region
White Pulp Region
What is the in red pulp region of the spleen (3)? Does it take up the majority of space? How does it stain?
Red Pulp region has: RBC, sinusoidal capillaries = splenic sinuses, splenic chords
The vast majority of spleen
Stains eosinophilic
What are splenic sinuses?
Discontinuous sinusoidal capillaries in the red pulp region of the spleen
What are splenic chords?
Reticular fibers which serve for an attachment point for macrophages, dendritic cells, B cells in the red pulp region of the spleen
Why are B cells attached to the splenic chords in the spleen?
They are positioned close to the splenic sinuses so they can pump antibodies into the capillary
Why are macrophages attached to the splenic chords in the spleen?
Positioned close to the splenic sinuses so they can engulf RBC and microbes
What is in the white pulp region of the spleen? How much space does it take up? How does it stain?
B cells, T cells, central artery, PALS, germinal center
Minority of space
Basophilic Stain
What is PALS?
Periarterial lymphatic sheath
When B and T cells exit from the arteriole they form a sheath
What is the central artery in the white pulp region really?
Arteriole of the splenic artery
What is the matrix region in the spleen? What kinds of cells do you find here?
Creates a border between white and red pulp regions
T cells, dendritic cells, macrophages
If lymphocytes become activated in the spleen they move off to the side to form a _________
Lymphatic nodule with a germinal center
