Chapter 5, Diseases of the immune system Flashcards
innate immunity definiton
(natural, or native immunity) mediated by cells and proteins that are always present, poised to react against infectious pathogens.
these cells are the 1st line of defense and the 1st to react.
they also have mechanisms to clear dead cell debris.
define hypersensitivity disorders?
the immune system causing tissue injury and disease
define adaptive, specific, acquired immunity
an immunity that is normally silent but responds to infectious agents. Since many pathogens have evolved to resist innate immunity and thus protection from the requires the specialized and powerful adaptive immunity/acquired or specific immunity.
what are recognized by the innate immunity?
phagocytes, dendritic cells and many other cells, such as epithelial cells, express receptors that sense the presence of infectious agents and substances released from dead cells.
these are called PAMP (pathogen-associataed molecular patterns)
what are the components of the innate immunity called that are responsible for pathogen recognition?
- pathogen-associated molecular patterns (shared among microbes of the same type)
- damage-associated molecular patterns (released from injured and necrotic cells.
- pattern recognition receptors (cellular receptors that recognize these molecules) 100 different receptors are used to recognize 1000 molecular patterns.
where are receptors of the innate immunity located?
everywhere; in the cell membrane for extracellular recognition, in endosoms for ingested substance detection and cytoplasm.
types of innate immunity receptors? best known receptors?
-toll-like receptors (these activate transcripton factors that stimulate the production of several membrane proteins to mediate inflammation, anti-viral cytokines (interferons). proteins promote lymphocyte activation, even more potent adaptive immune response.) TLR recognize, LPS (lipopolysaccharide) endosomal TLRs recognize viral and bacterial RNA and DNA
NOD-like receptors and inflammasome. activation of which form the cytokine interleukin-1 (IL-1) which recruits leukocytes and induces fever.
NODS recognize: uric acid and ATP and ion distrubances (K concentration)
-C-type lectin receptors (CLRs) in macrophages membrane
-RIG-I recognize RNA
-DNA sensors recognizes DNA
They (NOD) signal via a protein complex called the “inflammasome” which activates Caspase-1 which cleaves interleukine-1 to generate IL-1 which causes acute inflammation when secreted.
what are the 2 mechanisms by which the innate immunity provides defense.
- inflammation: complement activation trigger components of inflammation.
- anti-viral defense: type I interferons produced in response to viruses act on infected and infected cells and act to prevent replication and digest viral nucleis acids. They also serve to activate he more powerful adaptive immune response.
name the 2 type of adaptive immunity?
-humoral immunity: antibodies made by B-lymphocytes
-cell-mediated (cellular) immunity mediated by T-lymphoctes.
Antibodies protect from extracellular pathogens in blood and mucosal surfaces.
T-cells directly kill via cytotoxic T-cells or activate phagocytes.
where do T and B lymphocytes mature from?
-T lymphocytes mature in thymus
-B lymphocytes mature in bone marrow
each T or B cell expresses only one type of receptor
what are the receptors on B and T cells called?
B-cell (antibody)
T-cell (T-cell receptors)
there is massive diversity in the structure of these receptors.
define Clonal selection?
a process proposed to explain how a single B or T cell that recognizes an antigen that enters the body. The antigen is selected from the pre-existing cell pool of differing antigen specificities and then reproduced to generate a clonal cell population that eliminates the antigen. (the cell that recognizes it is replicated)
phases of lymphocytes?
- naive lymphocytes (antigen receptors expression but no function)
- effector lymphocytes (eliminate microbes)
- memory lymphocytes (rapid response upon subsequent encounter with antigen)
function of T lymphocytes.
they help B-cells make anibodies for foreign antigens.
they recognize protein fragments on MHC displayed by cells via the TCR (T-cell receptor)
what is the TCR (T cell receptor) made of?
heterodimer of disulfide linked a- and b- chains that have a variable and constant region.
CD3 and ζ-chain do not bind antigen but initiate intracellular mechanisms upon antigen recognition.
what does CD4 and CD8 on T-cells bind to?
class II MHC = CH4 CD4+ cells help B cells produce antibodies by secrete soluble cytokines. help macrophages destroy what they ingested. class I MHC = CH8 (called cytotoxic T lymphocytes (CTLs) because they kill infected cells, and tumor cells.)
function of T-cells with CD28?
function as receptors for molecules called costimulators. control the migration of the T cells to different tissues.
what suppresses immune response.
regulatory T lymphocytes
what is MHC restriction?
T cell can interact with a self-major histocompatibility complex molecule and a foreign peptide bound to it, but will only respond to the antigen when it is bound to a particular MHC molecule.
Class I MHC
expressed on all cells surfaces that are nucleated expressed in 3 closely linked loci; HLA-A, HLA-B, HLA-C
has a conserved region for CD8+ binding.
has polymorphic a-chain noncovalently associated with invariable B2- microglobulin polypeptide.
binds moslty intracellular elements.
Class II MHC
encoded by HLA-D. class 2 are heterodimers with a- and b-chains. expression restricted to APC's (antigen presenting cells) dendritic cells, macrophages and B-cells binds extracellular elements. (has domain for CD4+)
How to B-lymphocytes recognize antigens?
via membrane bound antibody of the immunoglobulin M (IgM) class, expressed on the surface together with signaling molecules to form the B-cell receptor (BCR) complex.
IgM has large diversity due to rearrangement and assembly of a multitude of immunoglobulin gene segments.
what can B-cells respond to?
unlike T-cells that respond to MHC only, B-cells can respond to more chemical structure; soluble or cell-associated proteins, lipids, polysaccharides, nucleic acids, without the requirement of MHC.
when B cells are activated they secrete what?
they turn into plasma cells to secrete immunoglobulins: (5 classes)
IgG, IgM, IgA, which make up 95% of circulating antibodies
IgA: (mucosal secretions)
IgE, IgD.