L2 ( rework ) Flashcards
- Antigens, their properties
Antigen – is any substance (usually protein nature and sometimes
polysaccharide), that is recognized by the immune system as a foreign and
promotes development of an immune response.
Antigens are classified:
- Exogenous Ag – penetrating from outer environment, for example bacteria, virus.
- Endogenous Ag- autoantigens, for example persons own self antigens.
- Allergen – Ag promoting allergic reactions.
- Hapten – incomplete Ag that is unable to induce an immune response by itself, it require carrier molecule to act as a complete antigen.
- Alloantigens – Ags found in different members of the same species, for
example red blood cells Ags.
- Heterophile Ags - Ags found in the cells of different species.
—- Properties of Antigens
1. Foreignness : Only molecules that are foreign to the host are immunogenic.
2. Molecular size : Extremly small molecules such as amino acids or monosaccharides are usually not immunogenic.
3. Chemical nature
Antigens are mainly proteins and some are polysaccharides.
4. Physical form
Denatured antigens are more immunogenic than the native form.
5. Specificity
Depends on the specific active sites on the antigenic molecules (epitopes)
Antigens of microorganisms.
its devided into 2 types
-1- Antigens secreted by bacteria
1 - Exotoxins
2 - Enzymes
-2-Antigens related to bacterial cell
1- -antigen -part of the cell wall also known as O-specific polysaccharides
2- H-Antigen – that is part of the flagella
3- K-Antigen- Capsular polysaccharide is a surface associated virulence
4- F-Antigen – fimbrial antigen
Antigens of viruses
they are 2
a) Protein coat viral antigens
b) Soluble antigens (soluble nucleoproteins as in influenza)
- Viruses are very small organisms that can grow only inside living cells. Viruses usually have a relatively simple structure consisting of a nucleic acid core surrounded by a protein layer. Some viruses may also be surrounded by an envelope containing lipoproteins and glycoproteins
Superantigens. explain
- Superantigens are proteins that generate a powerful immune response by binding to Major Histocompatibility Complex class II molecules on antigen-presenting cells and T cell receptors on T cells
Antigens of the human body
- There are many blood groups in the human population including ABO, Rh, Kidd , Transfusion with ABO incompatible blood can lead to severe and
potentially fatal transfusion reactions. RhD is highly immunogenic and can lead to red cell haemolysis in certain settings.
What is Complements
Complement is a family of more than twenty different proteins in serum that function as a non-specific defense against infection. Normally, these proteins are in an inactive form, but specific signal can activate the first protein of the team. Functions:
• Bacterial cell membrane perforation
• Opsonization of microorganisms for further phagocytosis
• Triggering of vascular inflammotary reactions
There are 3 major pathways for complement activation: the classical, alternate and lectin pathway.
All three ways of activation of the complement end in the same way with the formation of a mebrane attack complex. The membrane- attack complex – causes per
foration of the bacterial cell wall.
Macrophages’ receptors;
Macrophages : are a type of white blood cell of the immune system that engulfs and digests pathogens, such as cancer cells, microbes, cellular debris, and foreign substances, which do not have proteins that are specific to healthy body cells on their surface
Phagocytosis;
is the process by which a cell uses its plasma membrane to engulf a large particle giving rise to an internal compartment called the phagosome. It is one type of endocytosis. A cell that performs phagocytosis is called a phagocyte.
The engulfing of a pathogen by a phagocyte
In a multicellular organism’s immune system, phagocytosis is a major mechanism used to remove pathogens and cell debris
Antimicrobial proteins;
- antimicrobial is an agent that kills microorganisms or stops their growth.[1] Antimicrobial medicines can be grouped according to the microorganisms they act primarily against. For example, antibiotics are used against bacteria, and antifungals are used against fungi. They can also be classified according to their function. Agents that kill microbes are microbicides, while those that merely inhibit their growth are called bacteriostatic agents
Heat shock proteins;
- Heat shock proteins (HSP) are a family of proteins that are produced by
cells in response to exposure to stressful conditions. They were first described
in relation to heat shock
Function: play an important role in protein stabilization such as assembling of multi-protein complexes
Interferon
- are a group of signaling proteins made and released by host cells in response to the presence of several viruses.
- Function: share several common effects: they are antiviral agents and they modulate functions of the immune system
NK (natural killer) cells
- NK (natural killer) cell: large granular lymphocytes , are a type of cytotoxic lymphocyte to the innate immune system
function: control several types of tumors and microbial infections by
limiting their spread and subsequent tissue damage
Neutrophils, mast cells, eosinophils
1- Neutrophils are the most abundant type of granulocytes and make up 40% to 70% of all white blood cells in humans. They form an essential part of the innate immune system
- function: have been associated with the secretion of substances of biological relevance
2- mast cells A mast cell (also known as a mastocyte or a labrocyte) is a resident cell of connective tissue that contains many granules rich in histamine and heparin.
- Functions. In response to exposure to a perceived pathogen, mast cells set off a rapid inflammatory response to outside invaders
3- eosinophils are motile phagocytic cells that play an important homeostatic role in providing defense against parasitic infections.
Function: of eosinophils are multifaceted, including antigen presentation,
Cytokines;
- Proteins that are produced and secreted by many different cell types,
• mediate inflammatory and immune reactions.
• principal mediators of communication between cells of the immune system
types and there function :
1 -Type I interferons (INF): driving an antiviral state in non-immune cells
as well as orchestrating antiviral immune responses through
2- Interleukins (IL) regulate cell growth, differentiation, and
motility
3- Tumor necrosis factor (TNF) plays important roles in diverse cellular events such as cell survival, proliferation, differentiation, and death.
4- Stem cell factor plays an important role in hematopoiesis (formation of blood cells).
5- Transforming growth factor–β
(TGF-β) plays an important role in wound healing, angiogenesis,
6- Chemokines play a vital role in cell migration through
venules from blood into tissue and vice versa
