Innate Immunity, cells, molecules, and communication mechanisms

What type, surface, and organs are involved in the defense mechanism of the skin barrier?

Type: Physical

Surface: Epithelial

Organs: Skin

What type, surface, and organs are involved in the defense mechanism of sebum production?

Type: Chemical

Surface: Epithelial

Organs: Skin

What type, surface, and organs are involved in the defense mechanism of desquamation?

Type: Mechanical

Surface: Epithelial

Organs: Skin

What type, surface, and organs are involved in the defense mechanism of respiratory mucociliary flow?

Type: Physical

Surface: Epithelial

Organs: Respiratory tract

What type, surface, and organs are involved in the defense mechanism of stomach acid?

Type: Chemical

Surface: Epithelial

Organs: Stomach

What type, surface, and organs are involved in the defense mechanism of coughing and sneezing?

Type: Mechanical

Surface: Mucosal

Organs: Respiratory Tract

What type, surface, and organs are involved in the defense mechanism of peristalsis?

Type: Mechanical

Surface: Smooth muscle cells, enteric neurons, interstitial cells

Organs: GI tract

What type, surface, and organs are involved in the defense mechanism of mucus production?

Type: Mechanical

Surface: Mucosal

Organs: Respiratory and GI tract

What does SALT stand for?

Skin-associated lymphoid tissues

What type of defense mechanism are skin-associated lymphoid tissues?

Not a direct physical/chemical/mechanical defense mechanism

What types of cells do SALTs consist of?

Consist of cells of the innate and adaptive immune system

What do SALTs serve as sites for?

Immune cell activation and proliferation in response to antigens encountered in the skin

Cells of the innate immune system

Keratinocytes and Langerhans cells (LCs)

Keratinocytes

-specialized epithelial cell

-can act as antigen-presenting cells (APCs) and secrete cytokines that induce local inflammatory reactions

Langerhans cells (type of dendritic cell)

can phagocytose, migrate from the epidermis to regional lymph nodes, where they differentiate and function as potent activators of skintrophic naive T cells of the adaptive immune system

Phagocytosis

the internalization of particulate matter by cells by a process of engulfment, in which the cell membrane surrounds the material, eventually forming an intracellular vesicle (phagosome) containing the ingested material

3 types of phagocytic cells

1. Macrophages

2. Neutrophils

3. Dendritic cells

What do phagocytic cells do?

Trap and kill pathogens

Trap and degrade cellular debris

Phases of phagocytosis

1. Chemotaxis

2. Adherence

3. Ingestion

4. Destruction

PRR’s

Pattern recognition receptors

PAMPs

Pathogen-associated molecular patterns

How do phagocytic cells recognize microbes?

By expressing PRRs that recognize PAMPs on the microbes

Expressing receptors for opsonins that are bound to the microbe

Opsonins

Molecules that facilitate phagocytosis by phagocytic cells

A particular complement protein

Certain kinds of antibodies

There are ____ kinds of PRRs

several

_____ and ____ can express the same PRRs and multiple PRRs at the same time

Macrophages and neutrophils

PRRs allow phagocytes to…..

recognize groups of pathogens like gram positive and gram negative bacteria

What happens when a PRR on a phagocytic cell interact with a PAMP on a microbe?

Signals are generated to the phagocyte to become activated and get ready to ingest and kill the microbe

What does TLR stand for?

Toll-like receptors

TLRs

Most important group among the PRRs on phagocytic cells

-more than 10 different TLRs identified

-being investigated to modulate inflammation

The interaction between the TLR and the PAMP allows for…..

-microbial recognition (attachment) followed by phagocytosis

-signals that activate genes in the phagocytic cell that result in the production of cytokines

Cytokines

Help to activate inflammation and aspects of the adaptive immune system

Main phagocytic cells

Macrophages and Neutrophils

Main function of dendritic cells

Antigen presenting cells

What family tree do neutrophils and macrophages stem from?

Myeloid cell family tree

What common progenitor do the neutrophils and macrophages come from?

-Common myeloid progenitor cells

-Granulocyte/macrophage progenitor

Macrophages main function is what?

Phagocytosis

Shared functions of macrophages and dendritic cells

Sentinel cells and antigen-presenting cells

Sentinel cells

Identifying and capturing microbes in tissues

Antigen-presenting cells (ACPs)

cells that trigger immune response through the presentation and process of foreign material

Other functions of macrophages besides phagocytosis

Secretory cells and wound healing

How do neutrophils respond to infection?

Called in by cytokines from sentinel cells

What is the first phagocyte to respond to infection?

Neutrophils

What do neutrophils specifically respond to?

Bacterial infections

Where do neutrophils reside?

Bone marrow and blood

Parts of the bone marrow where neutrophils reside

proliferation pool, maturation pool, storage pool

Where are neutrophils found in the blood?

Mature neutrophils are found in the blood initially

Circulating pool in blood (CP)

What we count in a CBC

Neutrophilia

Above normal concentration of neutrophils in the circulating pool

Marginating pool in blood

Neutrophils that adhere to endothelium