Lecture 25+26 Flashcards
What are the effector cells
Lymphocytes: B cells, T cells, and Natural killer
Where do T- lymphocytes differentiate?
what proteins do they express?
what are the subclasses of lymphocytes?
T-lymphocytes differentiate in the thymus
they express CD-3 and T-cell receptors (TCR)
T-cell receptors: recognize antigen attached to identification molecules (MHC molecules)
subclasses are:
T-helper cells (Th1 and Th2)
they recognize antigens presented by antigen presenting cells (APC)
express CD4
cytotoxic lymphocytes (CTL)
recognize antigens presented on cancer or viral infected cells
express CD8
How to activate T-helper cells?
what do they synthesize?
roles?
they activate by the MHC-Ag complex (between T-cell and APC)
TH1:
recognize Ag presented by APC
control intracellular pathogens
TH2:
recognize Ag presented by APC
initiate antibody mediated immune response for extracellular pathogens
they both synthesize interleukins
How are CTL’s activated and what do they target?
they are activated when MHC I-Ag and CTR bind
Kill target cells- cancer cells, viral infected cells, parasites, transplanted cells, cells infected with intracellular microorganism.
NK cells?
innate immunity
kill target cells similar to CTL
can release granzymes and perforins
express Fc marker: – recognize the Fc region of antibodies coating target cells
B-lymphocytes
what proteins do they express?
what type of immunity?
participate in humeral immunity
express antigen bindings site, B cell receptor, and MHC II
sub types of B-lymphocytes?
how are they activated?
plasma cells: production and secretion of antibodies
Memory B cells: respond to second encounter with the same antigen
activation by BCR - Ag complex
endogenous antigen pathway?
- Antigen proteasomal degradation
- Formation of Ag -MHC I complex(rER)
- Translocation of complex via Golgi
- Presentation of Ag -MHC I on plasma membrane followed by CD8⁺ (CTL) recognition
Exogenous antigen pathway?
- MHC II assembly in rER
- Translocation of MHC II to membrane
- MHC II displayed on cell surface
- Endosomal endocytosis of MHC II
- Exogenous Ag endocytosis
- Proteolytic degradation of Ag
- Formation of Ag –MHC II complex
- Display of Ag -MHC II complex on cell surface followed by CD4⁺T helper recognition
- Lysosomal degradation of failed of Ag-MHC II recognition
Innate response vs adaptive response
Innate or non-specific:
uses neutrophils, macrophages, mast cells, and NK cells
fast and non-specific
does not produce memory cells
Adaptive response or specific immunity:
Depends on initial recognition of antigens by B and T cells
slower and more specific response
produces memory cells
antibody mediated immunity vs cell mediated immunity?
adaptive
antibody:
used helper T cells, B cells, and plasma cells
release Ab that act on pathogen
cell-mediated:
specific T-cells
use granzymes and perforins
Diffuse lymphatic tissue?
non encapsulated accumulations of lymphocytes and other free cells (plasma cells, eosinophils, fibroblasts)
protects the body from antigens
initial immune response
located in the lamina propria (subepithelial tissue)
What cells are found in the lymphatic nodule
lymphocytes reticular cells (fibers) dendritic follicular cells (APC) macrophages (phagocytic and APC) follicular dendritic cells (lack MHC-II)
All about the thymus?
location- superior mediastinum
primary lymphoid organ
no afferent lymphatics
origin: 3rd pharyngeal pouch
what makes up the thymus?
cortex: immature T-lymphocytes and ERC
medulla: mature T-cells and ERC
inner medulla: lymphocytes are less concentrated
epithelial reticular cells- support cells and held together by desmosomes
Blood thymus barrier
found only in the cortex of the thymus
function:
prevent immature T-cells from contacting antigens
Hassall’s corpuscle
found only in the medulla of the thymus
made up of ERC
what are the parts of the lymph node?
capsule: DCT
outer cortex: abundance of B-lymphocytes and has lymphatic nodules
inner cortex (paracortex): lots of T-cells
medulla: cords and sinuses
cords: mainly B-cells, plasma cells, reticular cells
sinuses: contain lymph
hilum: blood vessels and nerves
lymph movement through the lymph node?
afferent lymphatic vessels
subscapular (cortical) sinus
trabecular sinus
medullary sinus
efferent lymphatic vessel
About the spleen?
location: left-posterior abdominal wall
origin: mesoderm
function: filtration of old blood cells
What does the parenchyma of the spleen consist of?
red pulp: contains cords of cells (cords of billroth) sinusoid capillaries surrounds the white pulp function: remove damaged blood cells
white pulp:
lots of lymphocytes
lymphatic nodules (splenic nodules/malpighian corpuscles)
a central artery surrounded by lymphocytes goes through the white pulp
trabeculae: passage of blood vessels into parenchyma
marginal zone
This zone filled with lymphocytes, along with APCs (antigen presenting cells and macrophages)
first come into contact with antigens
Waldeyer’s ring
contains the lingual tonsils, pharyngeal tonsils, and palatine tonsils
Defect in the development of the 3rd & 4th branchial
pouches & arches??
leads to the absence of the thymus gland
can be seen in DiGeorge syndrome
Lymphadenopathy
swelling of the lymph nodes
follicular hyperplasia: increase in the number and size of cortical lymphoid follicles (humeral response)
paracortical hyperplasia: expansion of the paracortical zone due to viral infection
sinus hyperplasia: Medullary sinuses are extremely prominent- draining necrotic tumor
