Immunology 1 Flashcards
What are the primary lymphoid organs?
Thymus and Bone marrow
What are the components of a lymph node
Follicle, Medulla, and paracortex
How many efferents and afferents for lymph node
many afferents, 1 or more efferents
What happens in the follicle
Site of B-cell localization and proliferation. In outer cortex. Primary follicles are dense and dormant. Secondary follicles have a pale central germinal center and are active.
What happens in medulla.
Consists of medullary cords (closely packed lymphocytes and plasma cells) and medullary sinuses. medullary sinuses communicate with efferent lymphatics and contain reticular cells and macrophages.
What happens in paracortex
Houses T cells. Region of cortex between follicles and medulla. Contains high endothelial venules through which T and B cells enter from blood. Not well developed in DiGeorge syndrome.
Paracortex enlarges in extreme cellular immune response (e.g. viral infection)
Sinusoids of spleen
Red pulp is on the outside containing RBCs and surrounds the white pulp which contains T cells, B cells.
Sinusoids and Lymphocytes
T cells in Periarterial lymphatic sheath (central arteriole is in the center of everything).
B cells in follicles within the white pulp of the spleen.
What is the marginal zone
Red pulp and white pulp, contains APCs and specialized B cells, and is where APCs present blood-borne antigens
What do macrophages do in the spleen
Remove encapsulated bacteria.
What does asplenia due path
Decreases IgM leading to decreased complement activation leading to decreased C3b opsonization and increased susceptibility to encapsulated organisms.
Encapsulated bacteria
SHiNE SKiS: Strep pneumo, HiB, Neisseria meningococcus, E. coli, Salmonella, Klebsiella, Groub B Strep
What results due to postsplenectomy?
Howell-Jolly bodies (nuclear remants); target cells; thrombocytosis
Thymus made from what
epithelium of 3rd pharyngeal pouches
lymphocyte cell layer
Mesenchymal origin
Thymus structure
Cortex is dense with immature T cells; medulla is pale with mature T cells and Hassall corpuscles containing epithelial reticular cells.
Where do T and B cells mature
Thymus: T cells
Bone marrow: B cells
What are the examples of innate immunity
PMNs, macrophages, monocytes, dendritic cells, NK cells (lymphoid origin), complement
How long for innate immunity to kick in
minutes to hours
Are physical barriers included in innate immunity
Yes, e.g. tight junctions, mucus, lysozyme, complement, CRP, defensins
What are toll-like receptors
pattern recognition receptors that recognize pathogen-associated molecular patterns (PAMPs):
What are examples of PAMPs
LPS, flagellin, ssRNA
How does adaptive immunity get its variation
Through V(D)J recombination
MHC-I loci
HLA-A, B, and C
MHC II locis
HLA-DR, DP, and DQ (P Q R)
What do MHC-I and II bind
I: TCR and CD8
II: TCR and CD4
MHC-I found where
All nucleated cells, no RBCs
MHC-II found where
Only on APCs
Difference between MHC-I and II
I reveals endogenous proteins, II reveals exogenous proteins
how are antigens revealed by the MHCs
I: antigen peptides loaded onto MHC I in RER after delivery via TAP peptide transporter
II: Antigen loaded following release of invariant chain in an acidified endosome
How are MHC I and II moved to the cell surface
I: Beta2-microglobulin
II: Unknown
Structure to MHC I and II
Both have peptide binding groove
I: alpha is main component and has the peptide binding groove, beta2-microglobulin is small
II: alpha and beta are extremely similar and together form the peptide-binding groove
HLA A3
Hemochromatosis
HLA B27
PAIR: Psoriatic arthritis, ankylosing spondylitis, IBD, Reactive arthritis (seronegative arthropathies)
HLA DQ2/DQ8
Celiac disease
HLA DR2
MS, hay fever, SLE, Goodpasture syndrome
HLA DR3
T1DM, SLE, Graves disease
HLA DR4
RA, T1DM (4 walls in a “rheum”)
HLA DR5
Pernicious anemia, hashimotos
NK cells MOA
perforin and granzymes to induce apoptosis of virally infected cells and tumor cells.
NK cells activated by
IL-2, IL-12, IFN-beta, and IFN-alpha Activated by nonspecific activation signal and/or absence of class I MHC on target cell surface
Can NK cells bind antibodies
Yes, antibody-dependent cell-mediated cytotoxicity (CD16 binds Fc region of bound Ig, activating NK cell)
What do CD4 t cells do
Make antibody and produce cytokines to activate other cells of immune system
Differentiation of T cells
Starts in bone marrow, then moves to thymus, then lymph nodes
Steps of T cell differentiation
T-cell precursor from bone marrow moves into thymus where CD4+CD8+ T cells are positively selected for in the cortex. Then in the medulla they are divided up into CD4+ and CD8+ cells individually. They then move into the lymph nodes to fully differentiate.
Positive selection
Thymic cortex. T cells expressing TCRs capable of binding surface self MHC molecules survive.
Negative selection
Medulla. T cells expressing TCRs with high affinity for self antigens undergo apoptosis.
Th1 from
IL-12
Th2 from
IL-4
Th17 cell from
TGF-beta and IL-6
Treg cell from
TGF-Beta
What are the APCs
B cells, macrophages, and dendritic cells
What are the signals for T cell activation
MHC II binds TCR on Thelper, MHC I binds Tc (cytotoxic) cells (signal 1)
Signal 2: Costimulatory signal given by interaction of B7 (Dendritic cell) and CD28 (T cell)
B cell activation and class switching
- Helper T activated (so it is already primed to the antigen?)
- B cell presents antigens on MHC II to TCR on Th cell
- CD40 on B cell binds CD40 ligand on Th cell (signal 2)
- Th cell secretes cytokines that determine Ig class switching of B cell. B cell activates and undergoes class switching, affinity maturation, and antibody production.
What do CD4 and CD8 do.
They bind MHC for activation from Dendritic cell, this activation does not occur with B cells.
Th1 function
Secretes IFN-gamma
Activates macrophages and cytotoxic T cells
What inhibits Th1 cells
IL-4 and IL-10 (from Th2 cell)
Th2 function
Secretes IL-4, IL-5, IL-6, IL-13
Recruits eosinophils for parasite defense and promotes IgE production by B cells
What inhibits Th2 cells
IFN-gamma from Th1 cell
How to macrophages interact with lymphocytes
Macrophages produce IL-12 to produce Th1 cells which produce IFN-gamma which stimulates macrophages
Must know heme synthesis
For BIOCHEM
What to CD8 T cells have
Cytotoxic granules with perforin; granzyme B-serine protease to activate apoptosis; granulysin: antimicrobial, induces apoptosis
What are Tregs
Suppress CD4 and CD8 T cell fector functions.
How to identify Tregs
Cell surface markers: CD3, CD4, CD25 (alpha chain of IL-2 receptor) and transcription factor FOXP3.
What do Tregs produce
Anti-inflammatory cytokines like IL-10 and TGF-beta
What makes up the antigen binding site of antibodies
The variable part of the light and heavy chains.
What part of antibody fixes complement
Fc portion of IgM and IgG fixes complement.