CH12 - Innate Immune Response

Nonspecific (natural/innate) immune response

Not specific to any organism, includes first line and second line of defense

First line of defense

Physical barriers, microbiota barrier, chemical barriers (surface protection)

Second line of defense

Phagocytosis, inflammation, fever, antimicrobial products (cellular and chemical)

Immunology

The study of all features of the body’s second and third lines of defense (response to infectious agents and allergies)

Antigens (markers)

White blood cells recognize these molecules on cell surfaces, allowing the immune system to identify whether a cell poses a threat and should be marked for destruction

What is a healthy immune system responsible for?

• Surveillance of the body

• Recognize foreign material

• Destroy pathogens

• Recognize macromolecules as self or nonself

Pattern recognition receptors (PRRs)

• Innate immunity (second line)

• Recognize pathogen-associated molecular pattern molecules

Pathogen associated molecular pattern molecules (PAMPs)

• Markers that have different kinds of microbes in common

• Signal phagocytes and other defensive cells

Immune system

• Complex network of cells and fluids

• Lymphatic system

• Red bone marrow

• Circulatory system

Mononuclear phagocyte system (MPS)

Phagocytic cells enmeshed on the reticulum

Located in:

• Thymus

• Tonsils

• Spleen

• Lymphoid tissues

• Mucosa of gut/resp tract

Reticulum

• Connective tissues fibers that permeate tissues of the body

• Interconnects cells and connective tissue that surround the organs

Lymphatic fluid

Plasma-like liquid that transports WBCs, fat, debris, and infectious agents

Primary lymphatic organs (birth, maturation)

Red bone marrow

Thymus

Secondary lymphatic organs (activation, residence, functioning)

Lymph nodes

Spleen

Associated lymphoid tissues

Red bone marrow

• In flat bones and the end of long bones

• Produce RBCs

• B cells complete maturation here (then migrate to secondary organs)

Thymus

Site of T cell maturation (settle in lymph nodes and spleen)

Spleen

• Secondary lymph organ

• Filter for blood, removes worn-out blood cells

• Filters pathogens from blood

Whole blood consists of:

• Blood cells

• Plasma

• Serum

Hematopoesis

Production of blood cells

Stem cells

precursor of all new blood cells, become RBCs, platelets, and WBCs

Monocytes

Blood phagocytes that rapid leave the circulation, mature into macrophages and dendritic cells

Macrophages

• Large phagocytic cells,

• High capacity for killing microbes and cleaning up dead cells

• Antigen presenting cells

• Agranulocyte

Dendritic cells

Reside in tissues and MPS, process foreign material and present to lymphocytes (antigen-presenting)

Lymphocytes

• T cell

• B cell

• Natural killer cells

• NKT cells

• Gamma-delta T cells

Neutrophils

Short-live phagocytes in blood, engulf and kill bacteria. Primary component of pus, high neutrophil count = bacterial infection

Basophils

Function in inflammatory events

Eosinophils

active in protozoal, helminth, and inflammatory reactions

Mast cells

Specialized tissue cells similar to basophils that triger local inflammatory reactions, such as allergic symptoms

Cytokines

Regulate, stimulate and suppress cell development, inflammation, and immunity

Produced by monocytes, macrophages, lymphocytes, fibroblasts, mast cells, platelets, and endothelial cells

First line of defense

Physical, microbiota, and chemical barriers that impede the entry of microbes and foreign agents, whether living or not (inborn, nonspecific)

Mucous membranes

digestive, urinary, and respiratory tracts and of the eye

Defensins

antimicrobial peptides secreted from the skin, found in various body secretions

Lysozyme

Found in tears, sweat, and saliva, lyses gram positive bacteria

Iron binding proteins

Lactoferrin & transferrin

Second line of defense

Phagocytosis, inflammation, fever, antimicrobial proteins

Leukocytes

white blood cells, in two categories, granulocytes and mononuclear cells

Granulocytes

have a granular cytoplasm that contains digestive enzymes and other microbial chemicals

• Eosinophils

• Basophils

• Neutrophils

Mononuclear leukocytes (agranulocytes)

• Monocytes

• Lymphocytes

5 types of leukocytes

• Neutrophils

• Lymphocytes

• Monocytes

• Eosinophils

• Basophils

3 Phagocytes

• Neutrophils

• Monocytes

• Macrophages

Histocytes

• Alveolar macrophages

• Kupffer cells (liver)

• Dendritic cells (skin)

• Macrophages (systemic)

Pathogen associated molecular. patterns (PAMPs)

Signal molecules found on microbial surfaces recognized by phagocytes and other defensive cells (peptidoglycan and lipopolysaccharide)

Pattern recognition receptors (PRRs)

found on phagocytes, dendritic cells, endothelial cells, and lymphocytes, recognize and bind PAMPS

Signs of inflammation

• Redness

• Warmth

• Swelling

• Pain

• Loss of function

Extravasation

how cells leave the blood vessels

Chemotaxis

migration of cells from other sites

Margination

accumulation of WBC along blood vessel wall

Diapedesis

The migration of WBCs out of blood vessels into tissues

Selectins

molecules produced by endothelial cells that attract WBCs

Integrins

on surface of WBC to help adhere to endothelial cell

Fever purposes

• Inhibits rapid microbial growth

• Inactivates toxins

• Encourages rapid tissue repair

• Heightens phagocytosis

Interferon

Small proteins produced naturally by certain white blood and tissue cells, released by infected cell to warn surrounding cell to block replication of viruses

Interferons alpha and beta

produced by lymphocytes, fibroblasts, and macrophages

Interferon gamma

produced by T cells

Complement system

consists of over 30 blood proteins, destroy bacteria and certain viruses, parasits and nearby cells