Lymphoid structures Flashcards
A secondary lymphoid organ that has many afferents and one or more efferents; encapsulated, with trabeculae
lymph node
Functions of the lymph node
- nonspecific filtration by macrophages
- storage of B and T cells
- immune response activation
Site of B-cell localization and proliferation within the lymph node.
Follicle
Primary follicles in the outer cortex of the lymph node are dense and what?
dormant
Secondary follicles have pale germinal centers and are [active or inactive?]
active
What consists of medullary cords (closely packed lymphocytes and plasma cells) and medullary sinuses?
Medulla of lymph node
medullary sinuses communicate with
efferent lymphatics
medullary sinuses contain
reticular cells and macrophages
Region of cortex between follicles and medulla in the lymph node that houses T cells.
Paracortex
The paracortex contains high endothelial venues through which WHAT enter from blood
T and B cells.
What part of the lymph node is not well developed in pts with what syndrome?
DiGeorge
Paracortex enlarges in an extreme cellular immune response, such as?
viral infection
Head and neck drain to what node?
Cervical
Lungs drain to what node?
Hilar
Trachea and esophagus drain to what node?
Mediastinal
Upper limb, breast, skin above umbilicus drain to what node?
Axillary
Liver, stomach, spleen, pancreas, and upper duodenum drain to what node?
Celiac
Lower duodenum, jejunum, ileum, colon to splenic flexure drain to what node?
Superior mesenteric
Colon from splenic flexure to upper rectum drain to what node?
Inferior mesenteric
Lower rectum to anal canal (above pectinate line), bladder, vagina (middle third), and prostate drain to what node?
Internal iliac
Testes, ovaries, kidneys, uterus drain to what node?
Para-aortic
Anal canal (below pectinate line), skin below umbilicus (except popliteal territory) drain to what node?
Superficial inguinal
Dorsolateral foot and posterior calf drain to what node?
Popliteal
The right lymphatic duct drains
right side of body above diaphragm
The thoracic duct drains
everything below the diaphragm and the left side of the body above the diaphragm
into what does the thoracic duct drain?
junction of left subclavian and internal jugual veins
Long, vascular channels in red pulp with fenestrated “barrel hoop” basement membrane. Macrophages found nearby.
Spleen
Where in the spleen are T cells found?
Periarterial lymphatic sheath within the white pulp
Where in the spleen are B cells found?
In follicles within the white pulp
What do you call the area between the red pulp and white pulp of the spleen
the marginal zone
What types of cells are in the marginal zone?
APCs and specialized B cells.
What happens in the marginal zone?
APCs resent blood-bordn antigens
Macrophages in the spleen remove what type of bacteria?
encapsulated
Mechanism by wh/ splenic dysfunction –> increased susceptibility to encapsulated organisms?
decreased IgA –> decreased complement activation –> decreased C3b opsonization
Name the seven encapsulated bacteria
Strep pneumo HiB N meningitidis E coli Salmonella spp Klebsiella pneumo Group B strep
Postsplenectomy on peripheral blood smear
Howell-Jowell bodies (nuclear remnants), target cells, thrombocytosis
Encapsulated organ that is the site of T cell differentiation and maturation
Thymus
Thymus embryological derivation
Epithelium of third pharyngeal pouches
Lymphocytes within the thymus have what origin?
Mesenchymal
Thymic cortex is dense with what type of cells?
Immature T cells
Thymic medulla is pale with what type of cells and structures?
T cells and Hassall corpuscles containing epithelial reticular cells.
Name 6 components of innate immunity
neutrophils, macrophages, monocytes, dendtritic cells, NK cells (lymphoid origin), complement
Name three components of adaptive immunity
T cells, B cells, circulating antibodies
Innate immunity resistance is germline encoded, so it
persists through generations, does not change within and organism’s lifetime
Adaptive immunity resistance is achieved through
variation through V(D)J recombination during lymphocyte development; microbial resistance not heritable
Innate immunity response to pathogens (specificity and speed?)
nonspecific; occurs rapidly (minutes to hours)
Adaptive immunity response to pathogens (specificity and speed?)
highly specific, refined over time; develops over long periods; memory response is faster and more robust
Physical barriers that aid in innate immunity?
Epithelial tight junctions, mucus
4 secreted proteins of innate immunity
lysozyme, complement, CRP, defensins
1 secreted protein of adaptive immunity
immunoglobins
Key features in pathogen recognition in innate immunity
Toll-like receptors (TLRs): pattern recognition receptors that recognize pathogen-associated molecular patterns (PAMPs).
Examples of PAMPs
- LPS (gram-negative bacteria)
- flagellin (bacteria)
- ssRNA (viruses)
key features in pathogen recognition in adaptive immunity
memory cells: activated B and T cells; subsequent exposure to a previously encountered antigen –> stronger, quicker immune response
MHC is encode by what genes?
HLA
MHC function
present antigen fragments to T cells and bind TCRs
Where is MHC I expressed?
all nucleated cells (NB: not on RBCs!)
Where is MHC II expressed?
Expressed only on APCs
MHC I function
present endogenously synthesized antigens (e.g. viral) to CD8+ cytotoxic T cells
MHCII function
present exogenously synthesized proteins (e.g., bacterial proteins, viral capside proteins) to T-helper cells
Antigen peptides loaded onto MHC I in
RER after delivery via TAP peptide transporter
Antigen loaded following
release of invariant chain in an acidified endosome
MHC I mode of transport to cell surface
B2 microglobulin
MHC I loci
HLA-A, HLA-B, HLA-C
MHC II loci
HLA-DR, HLA-DP, HLA-DQ
With what HLA subtype is hemochromatosis associated?
HLA-A2
HLA-B27 subtype is associated with four diseases
PAIR
- Psoriatic arthritis
- Ankylosing spondylitis
- arthritis of Inflammatory bowel disease
- Reactive arthritis
With what HLA subtype is celiac disease associated?
HLA-DQ2 or HLA-DQ8
HLA-DR2 subtype is associated with 4 diseases
- multiple sclerosis
- hay fever
- SLE
- Goodpasture syndrome
Diabetes mellitus type 1 is associated with what HLA?
DR3 and DR4
SLE is associated with what HLA?
DR2 and DR3
diseases associated with HLA-DR3
DMT1, SLE, Graves
diseases associated with HLA-DR4
Rheumatoid arthritis, DMT1
diseases associated with HLA-DR5
Pernicious anemia –> vitamin B12, Hashimoto thyroiditis
How do natural killer cells induce apoptosis of virally infected cells and tumor cells??
Use perforin or granzymes
what is the only lymphocyte member of the innate immune system?
NK cells
NK activity is enhanced by 4 things
IL-2, IL-12, IFN-beta, IFN-alpha
what induces NK cells to kill
exposure to a nonspecific activation signal on target cell and/or to an absence of class I MHC on target cell surface.
NK cells also kills via antibody-dependent cell-mediated cytotoxicity - how does that work?
CD16 binds Fc region of bound Ig, activating the NK cell.
Three B cell functions
- Recognize antigen
- Produce antibody
- Maintain immunologic memory
How do B cells recognize antigen?
undergo somatic hypermutation to optimize antigen specificity
How do B cells produce antibody?
Differentiate into plasma cells to secrete specific immunoglobulins
How do B cells maintain immunological memory?
memory B cells persist and accelerate future response to antigen
CD4+ function
help B cells make antibody and produce cytokines to activate other cells of immune system