Properties and Overview of Immune Responses Flashcards
Immune System
The cells and molecules responsible for immunity
Immune Response
The collective and coordinated response of the cells/molecules of the immune system against foreign substances
First record of artificially acquired passive immunity
Chinese children, circa 15th century, inhaled powder of dry smallpox pustules
Innate immunity
Is essential for defending against microbes in the first few hours or days after infection, before adaptive immune responses have developed. Innate immunity is mediated by mechanisms that are in place even before an infection occurs (hence innate) and that facilitate rapid responses to invading microbes.
Adaptive immunity
The adaptive immune response is mediated by cells called lymphocytes and their products.
The three principal components of the innate immune system
- Physical and chemical barriers
- Phagocytic cells
- Blood proteins
Cardinal features of adaptive immune system
- Specificity and diversity
- Memory
- Self tolerance
Epitopes
Specific parts of a macromolecule that is recognized by a lymphocyte
Clonal Selection
The lymphocytes are selected by antigens when the membrane proteins present in the former recognize the antigens
Clonal Expansion
Selected lymphocytes are cloned rapidly increasing thousand of times
Diversity
The ability of the lymphocyte repertoire to recognize between 10^7 and 10^9 different epitopes
Memory
The subsequent responses to a pathogen are quicker and stronger than the first, memory cells are created after first exposure and these are more numerous and more specific to the pathogen than naive lymphocytes able to recognize the same pathogen.
Self Tolerance
The ability of the immune system to attack foreign antigens but not self antigens.
The two types of adaptive immunity
Humoral immunity and Cell-mediated immunity
Humoral Immunity
Mediate by molecules present in the body and mucosal secretions called antibodies, they are secreted by lymphocytes B. They neutralize antigens outside of cells.
Cell-mediated Immunity
Mediated by lymphocytes T, they neutralize antigens present inside phagocytes and other cells.
Active Immunity
Immunity acquired after exposure to the antigen.
Passive Immunity
Immunity characterized by the transference of antibodies and effector cells from an immunized individual to an individual who has not encountered the antigen.
Antigens
Molecules that bind to specific lymphocyte receptors, even if they don’t elicit an immune response.
Immunogens
Substances that elicit immune responses.
Opsonins
Proteins from the immune system that coat antigens in order to mark them for phagocytosis
Dendritic cells
Capture antigens, transport them to secondary lymphoid organs and present to naive T lymphocytes
Lymphocytes that have not responded to antigen
Naive
Cytokine
A large group of proteins that are used for the regulation and coordination of the immune system. All cells of the immune system secrete at least some cytokine, and have receptors for at least some.
Chemokine
A subgroup of the cytokines that regulate cell migration and movement.
Immune response by B lymphocytes to protein require…
Activating signals from CD4+ helper T cell
Pollysacarhides and lipids stimulate the secretion of antibodies of class
IgM
Proteins stimulate the secretion of antibodies of class
IgG, IgA and IgE
IgG
Coat microbes and mark them for phagocytosis and activates the complement system
IgM
Activates the complement system
IgA
Secreted by mucosal epithelia and prevent the entry via gastrointestinal and respiratory tract
T lymphocytes recognize…
Peptides bound to MHC proteins, thus only respond to cell surface-attached antigens
Cytotoxic T Lymphocytes (function)
Secrete molecules that kill other cells
Eosinophils
Able to kill parasites, which are generally too large to be killed by lymphocytes
Only cells capable of specifically recognizing antigens
Lymphocytes
Function of CD8+ CTLs
Kill cells that are infected by pathogens
