Immunology Exam 1

Innate Immune Response

immediate, not specific, no memory

adaptive immunity

memory, delayed, specific

inflammation

kicks starts everything, immediate

mast Cells

innate response, in tissues, degranulation

macrophages

in tissues, innate response, create and release cytokines, antigen presenting cell, phagocyte

dendritic cells

in tissues, innate response, antigen presenting cell, takes piece of antigen to lymph node & acts as a bridge to activate adaptive immune response

innate response -- as it pertains to a splinter

blood vessels swell and become permeable allowing complement to leak out, monocytes leave and enter tissues becoming DC's and macrophages, neutrophils enter tissue via diapedesis, DC's grab piece of bacteria (antigen) and go to lymph nodes, degranulation of mast cells once their receptors have recognized the presence of bacteria

presence of what means bacteria is present?

peptidoglycan and LPS (MAMP's)

neutrophil job

eat and destroy

complement can be activated via 3 pathways

classical, mannose-lectin, and alternative

C3 converts

C3bBb

C3 converts (C3bBb) works by

pro=inflammatory, opsonization, and formation of membrane attack complex (C56789) to kill bacteria

complement is

a set of proteins made in the liver that circulates in the blood in which C3 converts is the main activator

C3 is a potent...

opsonized -- aids in phagocytosis (for macrophages and neutrophils)

TLR's

toll-like receptors -- on innate system molecules that recognize MAMP's and turn on activation

B-cell and T-cells make what when activated?

(hard to activate, needs 2 signals) B-cell makes plasma and memory cells, T-helper cells make TH1, TH2, etc. and memory cells

2 functions of B/T cells after activation

clonal expansion and differentiation

job of plasma cell

make antibodies

b-cell activation

happens when antigen binds to b-cell receptor and causes cloning and differentiation

antibodies can

opsonize, activate complement, and neutralize/destroy activity

C3 cleaving into C3a and C3b...

activates pathway

what makes C3 special?

high-energy thirster bond that when cleaved become exposed and bonds to whatever is closest with an amine or hydroxyl group (h2o or protein)

role of C3b

binds to bacteria's surface to help in quick and easy phagocytosis

C3b --> c3bBb --> c3bBbC3b --> C5 converts --> C5a and C5b --> C5bC6C7C8 --recruit C9--> C56789 -->

formation of MAC which forms pore that kills the cell via phagocytosis

C3bBbC3b

C5 converts

propertin

protein that stabilizes C3b onto the bacteria surface to ensure cell death

role of DAF

prevents C3bBb binding to our own cells

role of MCP

recuits factor i to inactive C3 convertase

Anaphalotoxins

C3a and C5a are involved with swelling and increased dilation and permeability of blood vessels

defensins

small proteins found in mucosal surfaces that disrupt bacterial membranes --> are amphipathic

Induced Innate response occurs when?

3-5 hours to 3-5 days, happens in pathogen escapes complement phagocytosis

Goal of TLR signal transduction

create cytokines

ligand of TLR4

LPS

MyD88 role

integral adaptor protein

MyD88 --> IRAK4 -P-> TRAF6 -P-> IKK -P-> IKB -releases-> NFKB -promotes transcription-> production of cytokines synthesize in cytoplasm

pathway of TLR4

role of CD14 and MD2

accessory proteins that help bind LPS to TLR4 which begins signal transduction

pro-inflammatory cytokines

IL-1-beta (cytokine), TNF-alpha (cytokine), IL-6, CXCL8, IL-12

CXCL8

chemokine, recruits neutrophils to a specific area

IL-1beta

works in autocrine fashion

why does diapedesis have to happen?

cells in the blood are moving fast with pressure, they need to slow down in order to go into the tissues (specifically neutrophils)

Describe diapedesis

there's an infection, CXCL8 is made by macrophages, selecting, ICAM, and CXCL8 are made, neutrophil interacts with ICAM and slows but continues to move and hits CLCX8 and slows further, allowing the neutrophil to leave the dialated vessel and enter the tissues because integrins and selecting on the outside of the tissue are in a row, but aren't super tight.

how monocytes enter the tissue

similar to neutrophil diapedesis involving rolling and slowing down before entering the tissue

FMET receptor

recognizes bacteria as methionine is a big player -- bacteria start all their proteins with FMET

neutrophils kill bacteria how?

via phagocytosis, but also have granules but don't release them into environment, oxidative burst, non-oxidative means too

Describe how neutrophils kill bacteria through the production of super oxide

NADPH + O2 ---NADPH oxidase---> NADPH +2O2- + H+ ---superoxide dismutase---> H2O2 + O2 ---catalase---> H2O + O2

Why doesn't super oxide kill the neutrophil?

Because an enzyme,e (superoxide dismutase) works to break down super oxide in the vacuole almost immediately after it's produced

Chronic Granulomatic Disease (CGD)

When people cannot create NADPH oxide meaning they cannot produce superoxide. They succumb to early deaths via bacterial infections

Neutrophil Extracellular Trap (NET's)

occurs at the end of a neutrophil's life when bacteria is recognized in which neutrophils create a net or web like structure that traps bacteria and can kill them

How do NET's kill bacteria

traps them, net is made up of antimicrobial peptides and defensins that kill bacteria

cytokines IL-1beta, IL-6, and TNFalpha cause what?

cause liver to make acute-phase proteins (including C-mannose binding lectin), bone marrow releases neutrophils, & increase body temperature,

Induced Innate Response proteins

MASP 1 and MASP 2

Function of MASP 2

mannose-binding lectin binds mannose sugar food on surface of many bacteria. One MASP2 cleaves itself, then cleaves the other MASP2. Then, it cleaves C2 (C2a and C2b) and C4 (C4a and C4b) which produces C4bC2a, a C3 CONVERTASE

what's C4b's job

just like C3b, it attatches to the surface of bacteria to help in phagocytosis. From here, everything from the alternative pathway is the same

Predict phenotype of someone lacking MASP2?

Mannose-binding lectin and bacteria would do nothing. They would sit together as there would be nothing to cleave, complement pathway would never become activated.

Part of classical complement activation pathway

C-reactive protein is made, C1 binds to CR protein and C1 has MASP-type activity and cleaves C4 and C2.

Difference between classical and mannose-binding lectin pathways?

classical binds CR protein, where mannose-lectin binds mannose.

Interferon response

signaling to other cells through production of alpha and beta interferons that cause it's neighbors to induce an anti-viral response as well as make it easier for NK cells to come kill infected cells

what happens when a liver cell is infected by a virus?

the binding of the virus caused NFkappaB to go transcribe (through phosphorylation) resulting in the production of interferons and cytokines (cause inflammation)

What do interferons do?

induce anti-viral response and allow natural killed (NK) cells to come kill infected cells

Type 1 interferons

alpha and kappa

Type 2 interferons

gamma

B-cell components

• membrane-bound antibody called a resting B-cell which is a version of an antibody that will be made later

• 2 heavy chains and 2 light chains held together via disulfide bonds

• hinge region that allows some movement/flexibility

• constant and variable regions

how many different B-cells are in your body

~10^9 -- each recognizing a different antigen

What contributes to the billion different B-cells?

somatic recombination and somatic hypermutation

where does an antigen bind to a B-cell?

variable region

5 isotopes of constant regions of an antibody

IgM, IgD, IgA, IgG, and IgE

how do the constant regions differ

they are good at different things (opsonization, etc.)

Linear epitope

recognizes certain amino acid sequences that are touching each other (straight line of main acids)

Discontinuous Epitope

one in which amino acids are in close proximity in the folded protein, but distant when unfolded.

variable region

the highest amount of variability occurs in this region at the end of the antibody at the receptor which recognizes different, specific antigens

locus/loci

specific location on a chromosome, we have 1 locus from mom and 1 locus from dad

Heavy chains include

V, D, J, and C regions

Light chains include

V, J, and C regions

How does somatic recombination happen?

when a B-cell matures, it chooses at random 1 V, D, C, and J region. This creates a million different combinations. These regions are cut and pasted together randomly.

Germ line

Make somatic cells

somatic cells

any cell not passed on

heavy chain locus

chromosome 14

light chain loci

chromosome 2 & 22

stem cell --some changes--> mature B-cell

somatic recombination

How does recombination work? What proteins are involved?

RAG proteins 1 & 2 (enzymes) recognize a sequence of DNA and cuts it at a certain spot before pasting it back together and removing what's not needed. Works at the V and J junction on light and heavy chains.

What would happen without RAG?

We wouldn't be able to make B (or T) cells

When does RAG cut and paste this DNA?

Between the germ-line and somatic recombination

After RAG cuts DNA...

there is an overhang sequence that TdT sees and adds random nucleotides to for genetic diversity

Why is each B-cell receptor slightly different?

This random addition of nucleotides makes up for the added difference

allelic exclusion

in reference to B-cell development, the fact that each mature B cell expresses only one of the two Ig heavy-chain or light-chain alleles. For each locus, the maternal allele or paternal allele is used.

stem cells

group of cells that can differentiate and become different cells, found in blood marrow, reservoir of germ lines, stem cells do not change

from stem cell to specialized cell

stem cell --> germ line cell --> differentiated cells

which pieces are joined first in somatic recombination of heavy chain?

D and J regions, followed by the V region, and the C region

Where does RAG do its job?

Between the V and J junction on the light and heavy chains

nieve mature B-cells can make what immunoglobulins?

IgM (C region mu) and IgD (C region delta) through alternative splicing of exons of mRNA

what's the benefit of somatic hypermutation?

increased diversity and makes better antibodies as it creates better receptors

The antigen binding region is mostly made up of what?

V (variability) region, but also J and D

constant region of IgM

Cmu

what happens to antigen binding if constant region is switched by IgA to IgG?

will bind same antigen, just be good at a different set of functions

heavy and light chains come together to do what?

make B-cell receptors

different antibodies recognize different amino acid sequences which means what?

that different antibodies can recognize and respond to different epitopes of the same antigen

purpose of granules in mast cells and neutrophils

assemble NADPH for oxidative burst and for their antimicrobial molecules like defensins

defensins functions

poke holes in membrane

purpose of lab paper

neutrophils require complement to mount an effective super oxide burst

what enzymes work to degrade super oxide to ensure neutrophil doesn't die?

superoxide dismutase and catalase