Introduction to Immunology

Interlinked

Redundancies

Regulatory Mechanisms

Simultaneous responses

Adaptive

Immunity/ The Defenders

Physical Barries

Innate Immunity

Adaptive Immunity

three major barriers

physical barriers

intact skin

commensal organisms/microbiota

respiratory

gastrointestinal

self-cleaning processes

coughing

sneezing

vomiting

diarrhea

urine flow

innate immunity

Activated immediately/ “on call”

Responses are generic

Sentinel cells

Inflammation

“Hard-wired” subsystems

adaptive immunity

Smart responses

Ultimate defense of the body

Not only destroys but retains memory

Intracellular/ Endogenous vs. Extracellular/Exogenous invaders

Long-lived populations of memory T and Bcells persist for a long time

cellular-mediated

Intracellular/ endogenous invaders (intracellular bacteria, viruses, protozoa)

T cells

Cytotoxic T cells- abnormal cell

helper T cells

provide a signal for adaptive immune responses

regulatory T cells

regulates immune response

humoral

body fluids

Extracellular/ exogenous invaders (mostly bacteria, fungi, protozoa, helminths)

B cells

produce antibodies

antibodies

protective molecules from serum

antibodies

Highly specific and bind only to the antigen and ensure its destruction.

antibodies bind

“neutralize” the toxin so that it is no longer toxic.

antigen

a foreign substance that stimulates an adaptive immune response

animal Bcells

are stimulated to produce antibodies that bind to antigens and ensure their destruction

single-dose toxin

1 week lag period

Corresponding B cells populations grow and begin to produce antibody

The amount of antibody/ amount of protection conferred during the first primary response is relatively small since there are few antibody Bproducing B cells.

2nd dose of toxin/2nd response

lag period is shorter

The amount of antibodies rises to a high level before declining slowly

Months or years – antibody detection

B cell’s ability to remember previous exposure to antigen.

Anamnestic response”

antibody mediated immunity

Antibodies produced after repeated injections can better bind andneutralize the toxin than those produced in the early immuneresponse.

Repeated injections generate memory cells and form the basis ofVaccination.

A secondary response can also be induced even though theresponse of the animal to the first antigen was so weak as to beundetectable.

cell mediated immunity

Survives only a few days before being rejected and destroyed by the recipient.

Foreign cells are recognized by the immune system.

Mediated by cytotoxic T cells- identifies and destroys the abnormal cell

Graft rejection, like antibody formationis a specific adaptive rejection.

It also involves the generation of longlived memory cells

It cannot be transferred from a sensitized to a normal animal by serum.

Only by living T cells- found in your spleen, lymph nodes or blood.

mechanism of adaptive immunity

ü Antibody-mediated responses and cellmediated systems.

ü Pass system

ü Trapped and processed- Dendritic/ macrophages

ü B cells or T cells

ü Next time, same exposure, cells will respond faster and with great efficiency.