Innate immunity is an antigen-nonspecific defence mechanisms that a host uses immediately or within several hours after exposure to almost any microbe. This is the immunity one is born with and is the initial response by the body to eliminate microbes and prevent infection. Innate immunity can be divided into immediate innate immunity and early induced innate immunity. In this section we will learn about immediate innate immunity.
- 11.1: The Innate Immune System: An Overview
- The body has two immune systems: the innate immune system and the adaptive immune system. Innate immunity is an antigen-nonspecific defense mechanisms that a host uses immediately or within several hours after exposure to almost any microbe. Innate immunity is the immunity one is born with and is the initial response by the body to eliminate microbes. Immediate innate immunity begins 0 - 4 hours after exposure to an infectious agent. Early induced innate immunity begins 4 - 96 hours afterward.
- 11.2: Defense Cells in the Blood: The Leukocytes
- The complete blood count (CBC) is a laboratory test that, among other things, determines the total number of both leukocytes and erythrocytes per ml of blood. In general, an elevated WBC count (leukocytosis ) is seen in infection, inflammation, leukemia, and parasitic infestations. Neutrophils are the most abundant of the leukocytes, normally accounting for 54-75% of the WBCs. Neutrophils are important phagocytes and also promote inflammation. Eosinophils normally comprise 1-4% of the WBCs.
- 11.3: Defense Cells in the Tissue - Dendritic Cells, Macrophages, and Mast Cells
- Most dendritic cells are derived from monocytes and are referred to as myeloid dendritic cells and are located throughout the epithelium of the skin, the respiratory tract, and the gastrointestinal tract, as well as lymphoid tissues and organ parenchyma. Upon capturing antigens through pinocytosis and, the dendritic cells detach from their initial site, enter lymph vessels, and are carried to regional lymph nodes where they present antigens to the ever changing populations of naive T-lymphocytes
- 11.3: Immediate Innate Immunity
- Immediate innate immunity begins 0-4 hours after exposure to an infectious agent and involves the action of soluble preformed antimicrobial molecules that circulate in the blood, our found in extracellular tissue fluids, and are secreted by epithelial cells. These include: antimicrobial enzymes and peptides, and complement system proteins. These preformed antimicrobial molecules are designed to immediately begin to remove infectious agents as soon as they enter the body.
- 11.4: Early Induced Innate Immunity
- Early induced innate immunity begins 4 - 96 hours after exposure to an infectious agent and involves the recruitment of defense cells as a result of pathogen-associated molecular patterns or PAMPs binding to pattern-recognition receptors or PRRs. These recruited defense cells include phagocytic cells (leukocytes such as neutrophils, eosinophils, and monocytes; tissue phagocytic cells in the tissue such as macrophages), cells that release inflammatory mediators and natural killer cells (NK cells)
- 11.3A: Pathogen-Associated Molecular Patterns (PAMPs) and Danger-Associated Molecular Patterns (DAMPs)
- 11.3B: Pattern-Recognition Receptors (PRRs)
- 11.3C: Cytokines Important in Innate Immunity
- 11.3D: Harmful Effects Associated with Abnormal Pattern-Recognition Receptor Responses, Variations in Innate Immune Signaling Pathways, and/or Levels of Cytokine Production
- 11.3E: Phagocytosis
- 11.3F: Natural Killer Cells (NK Cells) and Invariant Natural Killer T-Lymphocytes (iNKT Cells)
- 11.3G: Inflammation
- 11.3H: Nutritional Immunity
- 11.3I: Fever
- 11.3J: The Acute Phase Response
- 11.3K: Intraepithelial T-lymphocytes and B-1 cells
- 11.E: Innate Immunity (Exercises)
- These are homework exercises to accompany Kaiser's "Microbiology" TextMap. Microbiology is the study of microorganisms, which are defined as any microscopic organism that comprises either a single cell (unicellular), cell clusters or no cell at all (acellular). This includes eukaryotes, such as fungi and protists, and prokaryotes. Viruses and prions, though not strictly classed as living organisms, are also studied.
Thumbnail: A scanning electron microscope (SEM) image of a single human lymphocyte. (Public Domain; Dr. Triche National Cancer Institute).
Contributors and Attributions
Dr. Gary Kaiser (COMMUNITY COLLEGE OF BALTIMORE COUNTY, CATONSVILLE CAMPUS)