Innate Immunity Overview

Innate Immunity

• Innate immunity is the body's immediate response to foreign invaders. It's not dependent on prior exposure.
• Adaptive immunity is modified by prior exposure to infectious agents and involves the response of antigen-specific B and T lymphocytes to antigen. This includes the development of immunological memory.

Infectious Agents

• Viruses are too small to be seen by light microscopy and multiply only within living cells. They consist of nucleic acid in a protein coat. Size range: 10-100 nm
• Size ranges for other infectious agents are not specified.

Pathogen Damage

• Pathogens damage cells and tissues in ways not specified.

First Line of Defense

• Skin and mucosal membranes form the first line of defense against pathogens.
• Interactions between adjacent epithelial cells in the epidermis are critical junctions.
• Skin is not merely a passive barrier; it also has active defense mechanisms.

Initial Defense Mechanisms

• Mechanical, chemical, and microbiological defenses are the three initial defense mechanisms in various parts of the body.
• Examples of these mechanisms in different body parts are not specified (e.g., mechanisms in skin, tears, saliva, etc.).

Lysozyme

• Lysozyme is a peptide that hydrolyzes the B-1-4-glycosidic bond between NAG and NAM in bacterial cell walls. It's found in tears, saliva, and human milk.

Defensins

• Defensins come in two classes, alpha and beta.
• Examples of specific alpha defensins are HNP1-3, 4, 5, 6.
• Beta defensin examples are HBD1-3, 4

Mucus

• Mucus is a viscous and slippery substance primarily composed of mucin. It's secreted to protect mucous membranes.
• It lubricates and helps protect against infectious agents.

Mucins

• Mucins are glycoproteins that form a gel-like structure in mucus.
• They contain alternating glycosylated and non-glycosylated domains.
• There are 21 different human mucin genes.

Prokaryotes and Eukaryotes

• Prokaryotes lack a nucleus (0.1-10 micrometers).
• Eukaryotes have a nucleus (10-100 micrometers).

Multipotent/Pluripotent

• Multipotent cells can give rise to multiple cell types.
• Pluripotent cells can give rise to all cell types in an adult.

Hematopoiesis

• Hematopoiesis is the process of blood cell generation.
• Three major cell lineages are formed: myeloid, lymphoid, and erythroid.

Phagocytosis

• Phagocytosis is the cellular internalization of particulate matter, such as bacteria. It involves chemotaxis, adherence, membrane activation, phagosome formation, fusion, killing, and digestion of released products.

Neutrophils

• Neutrophils are a type of granulocyte with granules.
• Neutrophils die after phagocytosis and are engulfed by macrophages.

Granules

• Neutrophils contain primary (azurophil) and secondary (specific) granules.

Monocytes, Macrophages

• Macrophages are derived from monocytes, which migrate into connective tissue.
• Macrophages exhibit a lightly stained nucleus often horseshoe or kidney-shaped.

NK cells

• NK cells kill infected cells by releasing granules containing proteins.

White Blood Cell Counts

• The ratio of white blood cells to red blood cells is approximately 1:600-700.

Pathogen-Associated Molecular Patterns (PAMPs)

• PAMPs are unique molecular patterns associated with pathogens.

Pattern Recognition Receptors (PRRs)

• PRRs on leukocytes recognize PAMPs.

Gram-Negative vs Gram-Positive Bacteria

• Gram-negative bacteria have less peptidoglycan in their cell walls, external membranes with lipopolysaccharide and no (lipo)teichoic acid.
• Gram-positive bacteria have a thicker peptidoglycan layer and (lipo)teichoic acid.

Cytokines

• Cytokines are low-molecular-weight proteins acting as messengers between cells.

Cytokine Classes

• Pro-inflammatory cytokines (TNFα, IL-1, IL-6, IL-8) and anti-inflammatory cytokines (IL-1ra, sIL-1R, IL-10, IL-4, IL-11).

Inflammation

• Inflammation is characterized by 5 cardinal signs: pain, redness, swelling (edema), heat, and loss of function.
• Inflammation involves the acute events during early phases of tissue injury and the later, chronic phases from persistent damage.
• This includes the involvement of mast cells, granulocytes, and macrophages.

Complement Activation

• The complement system involves three pathways (alternative, lectin, and classical) that ultimately lead to the destruction of pathogens.

Complement Proteins and Regulation

• Complement proteins are regulated.