Anatomy exam 1 2021: immune lecture Flashcards
what are antigens made of?
usually made of a protein, but can be polysaccharides, lipids, nucleic acids complexed w a protein and polysaccharide
examples of innate immune cells
phagocytic cells (macrophages, dendritic cells, all granular lymphocytes)
what progenitor cells make innate? adaptive?
NK cells: what do they attack?
what kind of cell?
these are SPECIAL lymphocytes
these attack virus-infected cells or tumor cells ("transformed cells")
Humoral factors of innate immune system
Humoral factors of adaptive immune system
innate: cytokines and complement system
function of cytokines
to coordinate and enhance immune responses
(are small proteins)
what kind of molecules are the complement system?
what are they produced by?
produced by liver
what do complement proteins do?
once activated by abnormal circumstances, the complement protein will bind to pathogen membrane and create holes to lyse the organism (MAC attack) ;
or stimulate phagocytic cells
Specific/Adaptive Immune mechanisms
B and T cells recognize SPECIFIC DOMAINS of antigens
lymphocytes can modify receptors and change them to respond to varying number of antigen domains
after first exposure to antigen, memory calls and clonal expansion allow for quicker response second time (a few memory cells are waiting around until the antigen comes again)
what are lymphokines
type of cytokine secreted by T cells: specific/adaptive
MHC molecules per individual
each individual has a different "fingerprint" arrangement of MHC molecules
MHC1 vs II (cell they are found on, purpose)
MHC I molecules: found on all nucleated cells and displays all protein sequences actively synthesized by the cell (tattoo explaining what proteins it has within)
MHC II: found only on antigen-presenting cells (APC) and displays self proteins with partially digested foreign proteins to Helper T cells (mixes foreign antigen w some self proteins. Important bc t lymphocyte needs mhcII to help recognize foreign bc educated in thymus when developing)
Examples of antigen presenting cells
formation and location of dendritic cells
arise in the bone marrow and travel to lymphoid organs including the thymus
T cell Activation:
what must there be in order for it to recognize the foreign antigen btw?
why are T cells called "cell-mediated immunity"
because T lymphocytes actually bind to the foreign antigen
Cluster of Differentiation molecules (CD)
expressed by T cells... act as co-receptors for mediating T cell activation
Subsets of T cells (4)
Helper T cells:
Recognize and bind to antigen-MHC II complexes on APC
Interact with B cells to stimulate B cell differentiation into plasma cells
Cytotoxic (cytolytic) T cells:
Recognize “abnormal” MHC I on transformed cells (infected, tumor, transplanted)
Destroy transformed cells by 2 mechanisms:
Release perforins which induce cell membrane damage
Activate genes which regulate apoptosis (programmed cell death) in transformed cells.
Suppressor T cells: decrease activity of B and T cells.
Memory T cells
T-cell activation process
notice that cytokines help T cells mature and then t cell secretes more cytokines which help w growth of more t cells too`
cytokine roles w t cells (3)
cytokines help T cells mature during activation
and then t cell secretes more cytokines which help w growth of more t cells too
also: T helper cells secrete cytokines that attract other cells (including other cytokines) to direct things at scene of issue
activation of other T cells
and B cell differentiation into plasma cells.
Ab vs Ig
B cells synthesize both:
immunoglobulins which are membrane-bound in immature B cells and secreted by plasma cells.
Circulating immunoglobulins are referred to as antibodies (Ab).
Why is it called humoral immunity
Since circulating Abs bind to foreign antigens, it is referred to as humoral immunity.
what acts as a BCR?
Immature B cells express membrane-bound immunoglobulin (IgM) on their surface which, along with other proteins, acts as a B cell receptor (BCR) and serves as the antigen binding site. (see better pic)
How to inactivate antigens (antibodies)
Foreign antigen bind to the BCR, are endocytosed, partially digested and complexed with MHC II molecules.
B cells then act as APC allowing Helper T cells to bind to antigen.
Helper T cells secrete lymphokines which stimulate B cell differentiation into plasma cells as well as proliferation of Memory B cells.
After final differentiation into plasma cells, immunoglobulins are synthesized in a soluble form (antibodies) which are secreted.
((Immature B cells can’t secrete antibodies. Only plasma cells secrete antibodies!! ))
Antigen-antibody complexes are then cleared by complement cascade or by liver and spleen
Immature vs. mature vs. plasma cell
While maturing, expresses IgD on surface. Once differentiates into plasma cell, can now release immunoglobulins. First to release is IgM (early infection)
B-cells with non-complementary receptors to antigens
"Each B or T cell carries receptors for specific antigen domains. Therefore, under normal conditions, there will be very small numbers of each type of lymphocyte present in the body."
- Upon second exposure to an antigen, memory B and T cells undergo rapid proliferation (clonal expansion)
Histology of Lymphoid tissue: what to look for
purple dark blueish dots (either inflammatory response or lymphoid tissue)
DOTS FOR INFLAMMATION are outside the vessels
Diffuse vs nodular lymphoid tissue:
what is in it?
Diffuse: may contain B or T cells
Nodular: B cell accumulation; spherical... solitary or aggregates
pale areas in middle of activated nodules: immature B cells proliferating
Lymphoid tissue: what kind of organs can it be in?
where else can it be?
both non-lymphoid and lymphoid
mucosa ASSOCIATED lymphoid tissue (not a lymph organ)
is under the epithelium, in CT
exposed to external environments!
unique thing about them
Basically are distinct accumulations of MALT
Only lymphoid organ with a surface epithelium
Lymphoid tissue and underlying partial CT capsule
Lymphoid Organs (4)
type of lymphoid tissue
Palantine tonsils: located in lateral walls of oropharynx
stratified squamous surface epithelium
Diffuse and nodule lymphoid tissue
located in the posterior wall of the nasopharynx
pseudostratified columnar surface epithelium
enflamed pharyngeal tonsils
: Lingual tonsils: numerous
located at the base of the tongue
stratified squamous surface epithelium
Where is the thymus
Located in the superior mediastinum, anterior to the heart and great vessels.
Grows until puberty, then gradually regresses with adipocyte infiltration
trick question, there are none! no b cells
2 important parts, what happens in each
2 "lobules" formed from dense connective tissue
Cortex: Site of T cell maturation
T cells become immunocompetent in the cortex before entering the medulla
notice the capsule btw
in medulla: concentric layers of thymic epithelial cells and keratin...
How to T cells "learn" to recognize ___ antigens?
Thymic epithelial cells and dendritic cells ( another type of APC) present self protein sequences to developing T cells so they “learn” to recognize self proteins.
Endocytose and expose self-antigens to developing t cells
Autoimmune regulator (Aire) protein.
thymic epithelial cells and dendritic cells possess the Autoimmune regulator (Aire) protein.
This protein functions as a transcriptional activator that promotes expression of peripheral tissue –specific proteins in the thymus. In this manner, developing T cells are exposed to all self-antigens bound to MHC on epithelial cells or dendritic cells.
Cortical blood-thymus barrier
In the cortex, envelope developing T cells and form a barrier between developing T cells and the blood:
(protects them from foreign antigens, don’t want to mix up education on selfantigen education with foreign antigens!):
Continuous capillary endothelium on a basal lamina
Thymic Epithelial cells (main part of barrier)
Blood Supply of thymus
arteries, then arterioles. It the flows into capillaries in the cortex and then drains into venules in the medulla.
Cells that survive post thymus
Needs to get weak affinity at least. If does not, will undergo apoptosis.
They may bind really strongly and attack, also don’t want those. Are killed off by existing macrophages
Mature immunocompetent T cells recognize self proteins (have a “weak” interaction with self proteins) but don’t bind to and react strongly are allowed to pass to venules in the medulla and gain access to the circulation.
also, what is in M?
what is in P?
Notice the cortex and medulla
Nodules on outside: Nodules, B cells
T cells: paracortex (P) (inner cortex)
Medulla: medullay cords with lymphocytes, plasma cells, and macrophages and Lymph sinuses: spaces between cords surrounded by macrophages, reticular cells and fibers
Lymph nodes: how do the vessels leave and enter
what provides SUPPORTIVE FRAMEWORK
Afferent lymphatic vessels enter convex surface
Efferent lymphatic vessel exits hilum
reticular fibers offer supportive framework
Histological Lymph Flow
Lymph enters through the afferent lymphatic vessels
and flows through the subcapsular sinus,
then cortical sinuses,
then enters the medullary sinuses
and exits the efferent vessel.
SNAP CRACKLE MOP
white pulp... 2 components
white: areas around blood vessels
Periarterial lymphatic sheath (PALS). The PALS consists of T cells and surrounds central arteries and arterioles
Lymphoid nodules: located at intervals along PALS
(so, it has both B and T but T are closer to the vessel?
2 main components
Red pulp: mesh of the sponge
Reticular fibers surround sinusoidal capillaries (splenic sinuses )forming a “cage”
Splenic cords: Located around the sinuses, consist of many RBCs, WBCs, macrophages, plasma cells
marginal zone of spleen
between red & white pulp: macrophages involved in RBC breakdown
RBC breakdown: hemoglobin breakdown products then travel in the blood to the liver
Blood cell production in embryo and in some disease states in adult
Primary defense organ: Activation of B and T cells
Into spleen, into smaller and smaller vessels, in arterioles, goes to the red pulp instead of venules like normal
Has some closed circulation, but red pulp is mostly open circulation! Before sinusoidal capillaries, is in red puip
follicular vs parafollicular hyperplasia
Follicular hyperplasia: if response is mainly humoral, nodules in outer cortex enlarge due to B cell proliferation
Parafollicular hyperplasia: T cell activation
cancer of lymphocytes where it starts location
Different subtypes, usually manifests first in lymph nodes but can spread to other lymphoid organs and bone marrow
Characteristic Reed-Sternberg cells: tumor cells that arise mainly from activated B cells.
Different subtypes have different prognoses
Most tumor cells arise from B cells,
Usually manifests first in lymph nodes but may arise from any lymphoid tissue, very commonly arises from MALT
malt is better prognoses
can be fro t