immunology - the good

What is immunology

The study of the immunity

Why is immunology important in veterinary medicine

-Recovery from infection
-Vaccination to prevent further infection
-Allergy and autoimmunity
-Inflammation

What are the three arms of the immune system

-Innate immunity -Intrinsic immunity -Adaptive immunity

Adaptive immunity

the ability to recognize and remember specific antigens and mount an attack on them
1. Specificity
2. Memory

Myeloid lineage

the granulocytes, monocytes, macrophages, mast cells and dendritic cells, and the bone marrow cells that give rise to them.

Lymphoid lineage

All types of lymphocyte, and the bone marrow cells that give rise to them.
-NK cells
-Th cells
-Tc cells
-B cells
-Plasma cell/antibody/forming

What happens when we are infected with a microorganism

-Detect the microorganism
-Capture/phagocytose the microorganism
-Destroy the microorganism

Macrophages can detect

-Lipids
-Sugars
-Other invading molecules

Macrophage

large phagocyte found in lymph nodes and other tissues of the body

What can invading microorganisms be ingested by

Phagocytes

Oxidative burst

A large increase in the oxygen consumption of immune cells during phagocytosis of pathogens as the immune cells produce oxygen radicals to kill the pathogen.

Oxygen dependent killing

oxidative burst culminates in production of H2O2 and other toxic substances

Oxygen independent killing

Damage to microbial membranes
destruction to the bacterial cell wall
chelation of iron
digestion of ingested organism

Microbicidal activity includes

Oxygen dependent killing
-Oxygen independent killing

Lymphocytic activity includes

-Antigen processing
-Antigen presentation
-IL-1 Production

Innate immunity

Immunity that is present before exposure and effective from birth. Responds to a broad range of pathogens.

Intrinsic immunity

Series of factors that are capable of preventing virus replication - switched on by interferons

Antibody

A protein that acts against a specific antigen

Complement fixation

activation of the classical complement pathway can result in the specific rupturing of cells and some viruses
-Triggers complement cascade to invading pathogen

Fc receptor

An Fc receptor is a protein found on the surface of certain cells - including B lymphocytes, macrophages, neutrophils, and mast cells that contribute to the protective functions of the immune system.

** know primary and secondary response graph - exam question!!**

Lecture 2 - primary and secondary response graph***

heavy chains and light chains

Each B cell antigen receptor is a Y- shaped molecule with two identical ___ and two identical __

Fragment antigen binding

The forked end of the antibody is called the _______ region.

What is the constant region that binds to phagocytic cells

FC

Allotypic variation

Variation in the amino acid sequence of the heavy and light chain genes (inherited)

Idiotypic variation

Variation in the antigen binding domain (where protein binds to antigen)

Isotypic variation

is the heavy chain g,m,e,a,d and the light chain k or l

What do antibodies do

Bind to antigens on pathogens to disable and clump them together ready for phagocytosis

Epitopes can be

Linear or conformational

Linear epitope

Epitope of a protein recognized by antibody that consists of a linear sequence of amino acids within the protein's primary structure.

secondary response to antigen

after second contact with the same Ag, immune system produces a more rapid, stronger response due to memory cells - anamnestic response
- higher affinity due to affinity maturation!

Subclasses of IgG

IgG1, IgG2, IgG3, IgG4

IgG1

most abundant and versatile

IgG2

Neutralization, diffusion into extravascular sites

IgG3

most effective complement activator

IgG4

Which IgG cannot activate complement?

What immunoglobulin appears first, followed by what?

IgM appears first followed by IgG

IgM are good at destroying ________ because they have a lot of the same ____. Binds easily because it repeats

Bacteria, epitopes

IgM has low ____ and low _____

Low affinity and low avidity

What does IgM do

Neutralizes antigen, fixes complement
-Low affinity receptor on monocytes (FcmR)

IgA

-Dimeric or tetrameric structure
-Secreted immunoglobulin, resistant to proteolytic degradation
-Secretory component mediates transport across epithelial surfaces
-High affinity receptor on monocytes and neutrophils

IgE binds to ____ in the absence of antigen

Binds to fc receptor

IgE allows us to be immune to

parasites, but triggers a histamine response

High affinity receptor for IgE is expressed on _______ and _____. Lower affinity receptor on ______

Mast cells, basophils
Monocytes

The specificity of an antibody is due to

the variable portions of the heavy and light chains

Does IgM or IgG have a lower affinity?

IgM

Affinity

How tightly it binds

MADGE

IgM, IgA, IgD, IgG, IgE

IgD

-Expressed on surface of B cells during development
-Surface receptor for antigen
-Facilitator of immunity to respiratory bacteria

IgY

birds reptiles and amphibia
combined functions of IgE and IgG

What don't camelids make?

Light chains - can't make as many recognizing bodies, effects the specificity

Where do antibodies come from?

Produced by B cells

Where did the name B cell come from

Bursa derived (birds)

Ehrlich's side chain theory

certain cell had specific surface receptors for antigen that were present before contact with foreign substance

Clonal selection

antigens bind to specific receptors, causing a fraction of lymphocytes to clone themselves

Why does clonal selection occur?

Your body is constantly making B cells against everything, this process is stopped by clonal selection

Plasma cells are ____ factories

antibody

Are antibodies proteins

Yes

What happens if B cells aren't removed if they're not being used

Autoimmune response!

Virgin B cells

short-lived cells, when they leave the bone marrow they are already antigen-specific, have rearranged variable region genes, express both IgM and IgD at the cell surface
-Short lived, over 75% don't reach circulation

When B cells leave the bone marrow they are

Antigen specific and have antibody IgM and IgD on their surface

VDJ recombination

DNA encoding RNA is spliced to make the protein - creates variable regions of antibody (which is why you can make antibodies against anything)

Recombinases

Enzymes that catalyze integration and excision of DNA segments during site-specific recombination. (like vdj recombination)

isotype switching (class switching)

the process by which a B cell changes the class of immunoglobulin it makes while preserving the antigenic specificity of the immunoglobulin
-Heavy chain interaction

How does vaccination work

A small amount of dead or weakened microbe is injected - white blood cells make antibodies and the individual is now immune
-need to improve affinity, IgM is swapped to IgG - once it is spliced to make IgA it cannot go back!

Where does VDJ recombination occur?

Bone marrow during B cell maturation
VDJ is the heavy chain
VJ is the light chain

Allelic exclusion occurs in the

bone marrow

Allelic exclusion

Prevents the rearrangement of 2nd chromosome

where are IgM and IgD heavy chains produced (mature "virgin" B cell)

Bone marrow

Isotype (class switching) occurs where and when

Lymphoid tissue after stimulation of virgin B cell with antigen

Affinity maturation occurs where

Lymphoid tissue

What immunoglobulin occurs with affinity maturation

IgG

What do you want to expand when you are performing a booster vaccination?

Want to expand B cells with the highest affinity

If you give a booster vaccine too soon what happens?

B cells don't go through affinity maturation, you are just selecting B cells with a low affinity not a high affinity

monoclonal antibodies

a collection of identical antibodies that interact with a single antigen site

Hybridoma cell

cells formed by fusion of myeloma cell with plasma B cell

Where do B and T cells interact with antigens

Lymphoid tissue

B cell trafficking

Trafficking to lymph nodes

What moves antigens around

lymph

Dendritic cells

specialized white blood cells that patrol the body searching for antigens that produce infections

How to dendritic cells work

Long processes that trap antigens that stick to cell surface - trap virus

IgM responses have ______ affinity

Low affinity

Somatic hypermutation

-Enzymes cause point mutations in variable regions of Ig
-Changes antigen-binding specificity
Could be better, could be worse
-Self-reactive B cells generated by somatic mutation are deleted

How long do b cells live

3-4 days

Clonal expansion hypothesis

Rather than destroying antibodies forming cells to limit antibody production, the B cells can be silenced

How do B cells avoid making responses against self antigens

When B cells recognize antigen they are killed immediately

somatic hypermutation

mutation that occurs at high frequency in the rearranged variable-region DNA segments of immunoglobulin genes in activated B cells, resulting in the production of variant antibodies, some of which have a higher affinity for the antigen

IgM - Low ______, High _______, Low ________

low affinity, high avidity, low titer

IgG - Low _____, High _____

Low affinity, high titer

IgG - High ______ High _______

Affinity , titer

Positive selection

Interaction with MHC I and MHC II

T cell receptors - what do they do?

bind processed antigens together with the MHC molecules on the cells that present antigens to them

What type of animal are gamma delta T cells abundant in?

Ruminants

What do gamma/delta T cells do?

recognize a wide variety of peptides - protect mucosal surfaces
-May contribute to innate immune system (first line of defense)

Dendritic cells can instruct _____ to respond in the appropriate way for a pathogen

Helper T cells

Th1 cells

initiate inflammation and immunity by activating macrophages

Cellular immunity

immune response that relies on T cells to destroy infected body cells

Th2 cells favor what kind of response

humoral and they induce mast cell production

Humoral immunity

B cell proliferation
-class switching IgA, IgE
-Increase Ig production

Th17 cells promote

Neutrophil response