Innate immunity

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Innate immunity

Anti-viral immunity

type I IFNs (α/ß) or IFN-I

detect RNA and DNA viruses with two endosomal sensors, TLR7 and TLR9

primary source of IFN-I for antiviral responses

Stimulation of adaptive immunity (3rd line defense)

T cell activation and differentiation (Th1 and Th2)

Th2 -antibody-mediated immunity -extracellular parasites -asthma, allergy

Th1 -cell-mediated immunity and inflammation -intracellular pathogens -autoimmunity -inflammation

Activation of adaptive immunity

Interplay between innate and adaptive immunity

Inflammation and cell recruitment

Chronic inflammation

• Scarring • Amyloidosis • Neoplasia

Mechanism involves with:

Pro-inflammatory(IFN-γ)and anti-inflammatory (IL-4andIL-13)

Prolonged exposure to toxic pathogens

Acute inflammation

Outcomes:

1. Local hemodynamic changes (vasoconstriction → vasodilation) 2. Increase in vascular permeability 3. Extravasation of leukocytes 4. Phagocytosis 5. Outcome of inflammatory response

Features:

5 cardinal signs: redness, increased heat, swelling, pain, loss of function

Involves the innate immune system

Innate immune response (2nd line defense)

Humoral substances of innate immunity

Cytokines, mediators, complement system

Peripheral blood immune cells

Monocytes

Basophils

Eosinophils

is involved in host protection against parasite infection and immunopathology in hypersensitivity disease

Dendritic cells

are professional antigen-presenting cells

Neutrophils

are important effector cells in the innate arm of the immune system.

NK cells

-recognize MHC I -Produce high levels of cytokines

Tissue innate immune cells

Macrophages

secretes inflammatory cytokines that support immune responses.

Intraepithelial lymphocyte (IELs)

an effective first line of defense

are lymphocytes found in the epithelial layer of mammalian mucosal linings

Microbe recognition by innate immune cell PRRs

Major type of PRRs

C-type lectin receptors (CLRs)

RIG-like receptors (RLRs)

NOD-like receptors (NLRs)

Toll-like receptors (TLRs)

PRRs can be found on the innate immune cells

PRRs are able to recognize molecules associated with pathogens i.e. PAMPs and DAMPs

Innate immune cell activation by PAMPs and DAMPs

DAMPs

Endogenous stimuli

Derived from host cells such as tumor cells, dead or dying cells, products released from cells, tissue damage, etc

PAMPs

Exogenous stimuli

Derived from components of microorganisms (pathogens)

Characteristic of innate immunity

No memory

Non-specific responses

Rapid/quick response

Barrier defenses (1st line defense)

Biological barriers

ex. normal flora

is the term used to describe various bacteria and fungi that are permanent residents of certain body sites

Chemical barriers

ex. low stomach pH, lysozyme

Mechanical/Physical barriers

ex. skin

tightly joined

preventing microbes from reaching tissues