Introduction to Immunology

Primary function of the immune system

To detect injury and return tissues to homeostasis.

Chronic inflammation

The result when tissue cannot be repaired or an infection cannot be cleared.

Infection vs. Disease

Infection is microbial invasion; disease is the resulting clinical damage or dysfunction.

PAMPs

Pathogen-Associated Molecular Patterns; recognized by the innate immune system.

DAMPs

Damage-Associated Molecular Patterns; signals of tissue damage recognized by innate immunity.

Innate Immunity (Timing)

The immediate response, acting within minutes to hours of microbial invasion.

Adaptive Immunity (Timing)

A slowly developing response, taking days to weeks to become fully effective.

Soluble components of Innate Immunity

Complement, antimicrobial proteins/peptides (defensins), and cytokines.

Cellular components of Innate Immunity

Phagocytosis, reactive oxygen/nitrogen species, and induction of adaptive responses.

Humoral Adaptive Immunity

Involves B cells, immunoglobulins (antibodies), and the complement system.

Cell-mediated Adaptive Immunity

Involves T cells and Antigen-presenting cells (like Dendritic cells).

Extracellular pathogen defense

Cell-independent killing (complement) and antibody opsonization for phagocytosis.

Intracellular pathogen defense

Cytotoxic T cells, NK cell cytotoxicity, and Helper T cell cytokines.

Immunologic Memory

The ability of adaptive immunity to provide enhanced protection upon repeated exposures.

Hematopoietic stem cell

The bone marrow cell from which all immune cells arise.

Primary lymphoid organs

Sites where precursor cells complete development, such as the Thymus and Bursa/Bone Marrow.

T cell maturation site

The Thymus.

B cell maturation site

The Bursa (in birds) or Bone Marrow.

Symbiotic microbes

Non-dangerous microbes on barriers (skin, GI tract) that can be beneficial.

Cost of immune response

Expansion of specific cells, production of mediators, and potential tissue damage.

Immune Over-function

Leads to allergy, hypersensitivity, or autoimmune disease.

Immune Under-function

Leads to primary immunodeficiency or susceptibility to infection.

Vaccines

Therapeutics that mimic natural infection to induce immune memory.

Immunotherapies

Treatments that exploit immune knowledge, such as inhibiting cancer-induced suppression.

Antigen-binding receptors

Highly specific, diverse receptors characteristic of the adaptive immune response.

Immediate Innate Immune Response

0 to 4 hours

little to no tissue damage

preformed soluble effector molecules and resident effector cells in the infected tissue

Induced innate immune response

4 hours to 4 days

Activation of resident cells

-Recruitment of effector cells

-Inflammation, Fever

-Acute phase response

-Soluble effector molecules and effector cells recruited and pathogen is attacked

Adaptive Immune Response

4 days until the defeat of the pathogen, defeat of the host, or the truce of the chronic disease

-Secondary lymphoid tissue is made aware of the infection

-Reactive B & T cells are identified in secondary lymphoid tissue

-B & T cells proliferate and mature to become effector cells

-Antibodies and effector T cells moves to infection

-Pathogen dies or host dies

hematopoietic stem cells -> Common lymphoid precursor -> 1. ____ 2. ____

1. B Cell

2. NK/T Cell Precursor

B Cell -> ____

Plasma Cell

hematopoietic stem cells -> Common Myeloid Precursor -> 1. , 2.

1. Megakaryocyte/Erythroid Progenitor

2. Granulocyte-macrophage progenitor

Megakaryocyte/Erythroid Progenitor -> 1. -> 2.

1. Megakaryocyte

2. platelets

Megakaryocyte/Erythroid Progenitor -> 1. -> 2.

1. Erythroblast

2. Erythrocyte

Granulocyte-macrophage progenitor -> 1., 2., 3.

1. Neutrophil

2. Eosinophil

3. Basophil

Granulocyte-macrophage progenitor -> Macrophage and dendritic precursor -> 1. -> 2., 3.

1. Monocyte

2. Macrophage

3. Dendritic Cell

Granulocyte-macrophage progenitor -> unknown precursor -> 1.

1. Mast Cell