Innate and Adaptive Immunity Flashcards
Outline innate immunity.
Innate immunity is always available to combat a wide range of pathogens immediately, but offers no lasting immunity and is not specific.
Innate immunity is one branch of immunity, and it involves phagocytes, macrophages, complement, and natural killer (NK) cells. It is also known as cellular immunity.
Outline adaptive immunity.
Adaptive immunity is one of two branches of immune response that produces a specific response and has the ability to develop immunological memory. It takes action 12 hours after pathogen exposure, and can last days.
Adaptive immunity has two subcategories: humoural and cell-mediated immunity. Humoural involves B lymphocytes, and cell-mediated involves T lymphocytes.
Define antigen.
Any substance that can be recognised and responded to by the adaptive immune system.
Outline the two wings of adaptive immunity.
The two wings of the adaptive immune system are humoural immunity and cell-mediated immunity.
Humoural immunity deals with pathogens extracellularly, whereas cell-mediated immunity deals with pathogens intracellularly. They are mediated as follows:
Name macrophages in the:
- Bone marrow/blood
- Liver
- Central nervous system
- Bone
- Kidney
- Bone marrow/blood: monocytes
- Liver: Kupffer cells
- Central nervous system: microglia
- Bone: osteoclasts
- Kidney: Intraglomerular mesangial cells
To protect the individual effectively against disease, the immune system must
fulfill four main tasks:
- 4.
-
Immunological recognition: the presence of
an infection must be detected. This task is carried out both by the white blood
cells of the innate immune system, which provide an immediate response,
and by the lymphocytes of the adaptive immune system. -
Immune effector functions such as the complement system of blood
proteins, the antibodies produced by some lymphocytes, and the destructive
capacities of lymphocytes and the other white blood cells. - At the same time the immune response must be kept under control so that it does not itself do damage to the body. Immune regulation, or the ability of the immune system to self-regulate, is thus an important feature of immune responses, and failure of such regulation contributes to conditions such as allergy and autoimmune disease.
- Protect the individual against recurring disease due to the same pathogen. A unique feature of the adaptive immune system is that it is capable of generating immunological memory.
Outline the common myeloid progenitor.
The common myeloid progenitor is the precursor of the macrophages, granulocytes, mast cells, and dendritic cells of the innate immune system, and also of megakaryocytes and red blood cells, which are not part of the immune system.
Outline macrophages.
Macrophages are resident in almost all tissues and are the mature form of monocytes, which circulate in the blood and continually migrate into tissues, where they differentiate. Macrophages are relatively long-lived cells and perform several different functions throughout the innate and adaptive immune response:
- One is to engulf and kill invading microorganisms. In this phagocytic role they are an important first defence in innate immunity and also dispose of pathogens and infected cells targeted by an adaptive immune response. Both monocytes and macrophages are phagocytic.
- An additional and crucial role of macrophages is to orchestrate immune responses: they help induce inflammation, which is a prerequisite to a successful immune response, and they secrete signalling proteins that activate other immune-system cells and recruit them into an immune response.
- In addition to their specialized role in the immune system, macrophages act as general scavenger cells in the body, clearing dead cells and cell debris.
What are the three types of phagocyte?
- Monocytes and macrophages
- Granulocytes (or polymorphonuclear leukocytes (PMN)): neutrophils, eosinophils, basophils.
- Dendritic cells
Outline granulocytes.
The granulocytes are so called because they have densely staining granules in their cytoplasm; they are also called polymorphonuclear leukocytes (PMN, PML, PMNL) because of their oddly shaped nuclei. There are three types of granulocytes neutrophils, eosinophils, and basophils-which are distinguished by the different staining properties of the granules. In comparison with macrophages they are all relatively short -lived, surviving for only a few days, and are produced in increased numbers during immune responses, when they leave the blood to migrate to sites of infection or inflammation. The phagocytic neutrophils are the most numerous and most important cells in innate immune responses.
Eosinophils and basophils are less ________ than neutrophils, but like neutrophils they have granules containing a variety of _______ and _____ ________, which are released when the cells are activated. Eosinophils and basophils are thought to be important chiefly in defence against _________, which are too large to be ingested by macrophages or neutrophils. They can also contribute to ________ inflammatory reactions, in which their effects are damaging rather than protective.
Eosinophils and basophils are less abundant than neutrophils, but like neutrophils they have granules containing a variety of enzymes and toxic proteins, which are released when the cells are activated. Eosinophils and basophils are thought to be important chiefly in defence against parasites, which are too large to be ingested by macrophages or neutrophils. They can also contribute to allergic inflammatory reactions, in which their effects are damaging rather than protective.
Outline mast cells.
Mast cells, whose blood-borne precursors are not well defined, differentiate in the tissues. Although best known for their role in orchestrating allergic responses, they are believed to play a part in protecting the internal surfaces of the body against pathogens, and are involved in the response to parasitic worms. They have large granules in their cytoplasm that are released when the mast cell is activated; these help induce inflammation.
Outline dendritic cells.
There are several kinds of dendritic cells. Most dendritic cells have long finger-like processes, like the dendrites of nerve cells, which give them their name. Immature dendritic cells migrate through the bloodstream from the bone marrow to enter tissues. They take up particulate matter by phagocytosis and also continually ingest large amounts of the extracellular fluid and its contents by a process known as macropinocytosis.
- Like macrophages and neutrophils, they degrade the pathogens they take up, but their main role in the immune system is not the clearance of microorganisms. Instead, the encounter with a pathogen stimulates dendritic cells to mature into cells that can activate a particular class of lymphocytes-the T lymphocytes.
- Mature dendritic cells activate T lymphocytes by displaying antigens derived from the pathogen on their surface in a way that activates the antigen receptor of aT lymphocyte.
- They also provide other signals that are necessary to activate T lymphocytes that are encountering their specific antigen for the first time, and for this reason dendritic cells are also called antigen-presenting cells (APCs). As such, dendritic cells form a crucial link between the innate immune response and the adaptive immune response.
- In certain situations, macrophages can also act as antigen-presenting cells, but dendritic cells are the cells that are specialized in initiating adaptive immune responses.
List the immunological components of innate immunity.
- Peptide antibiotics: on mucosal membranes, bind to pathogens and punch holes in them.
- Phagocytic cells
- Cell surface receptors
- Complement system
- Cytokines
- Soluble factors
- Natural killer (NK) cells
What is responsible for the recognition of pathogens and microbes? (molecular level)
Pattern recognition receptors (PRRs) are proteins expressed in cells of the innate immune system, and surface PRRs can recognise either pathogen-associated molecular patterns (PAMPs) or damage-associated molecular patterns (DAMPs).
- PAMPs: molecules associated with groups of pathogens, that are recognized by cells of the innate immune system.
Give an example of a cell-surface PRR.
- Toll-like receptor (TLR)
- C-type lectin receptor (CLR)
- Mannose receptor (Type I CLR)
Give an example of a TLR and it’s associated PAMP(s).
- TLR1:TLR2- Bacterial triacylated lipopeptides
- TLR2- Bacterial peptidoglycan, lipoprotein, lipotechoic acid, and porins
- TLR4- Gram ve- bacterial LPS, fungal mannans, parasitic phospholipids, viral envelope proteins, host heat shock proteins
- TLR5- Bacterial flagellin
- TLR2:TLR6- Bacterial diacylated lipopeptides and lipotechoic acid
Give some examples of receptors on the cell-surface of macrophages. What occurs after binding with their complementary item?
- LPS receptor (CD14)
- TLR-4
- Scavenger receptor
- Glucan receptor
- Mannose receptor
The macrophage contains different low-pH compartments and secrete defensins in order to remove pathogens.
