Host defences Flashcards
innate, first barriers
non-specific - complement antimicrobial proteins Phagocytes (neutrophils, macrophages) inflamation
adaptive defensives
induced by infection and specific, based on antigen
normal microbiome on skin secrete ____
secretes bacteriocin
- has antimicrobial substances: FA, lysozyme, AMPs (antimicrobial peptides), antibodies (if the host I immune)
mucous membrane
traps bacteria
complement system
set of blood and tissue protein that creates the pores in the pathogen membrane and induces lysis
- known as complement bc they complement the action of antibodies
phagocytes
cells that take up and digest pathogens
second line innate defence includes
complment system
phagocytes
inflammation
explain the complement system activation
two activation systems
- by antibodies
- by microbial cell wall components ( polysaccharid)
activating the complement system results in the formation of ___
a membrane attack complex (MAC) that causes lysis of some gram negative NO EFFECT ON GRAM POSITIVE
the membrane attack complex has no effect on ?
gram positive ( properly too much peptidylglycan)
MAC formation
complex process that involveds lots of C# proteins and ends in the creation of a pore in membrane which leads to the lysis of cell
major cell types in human blood
erythrocytes (RBC) WBC: (3) lymphocytes--> B cells, T cells ( helper and cytotoxic) granulocytes--> neutrophil monocytes-->dendrites and macrophages
three classes of WBC (leukocytes)
monocytes, granulocytes and lymphocytes
monocytes
turn to macrophages and dendritic cells
macrophages are phagocytic (along with neutrophil)
Granulocytes
cytoplasm contain granules (are lysosomes that contain hydrolytic enzymes)
- mast cells, neutrophils and basophils
- neutrophils are phagocytic and the main one
Lymphocytes
B cells: antibodies
T cells: T helper cells and cytotoxic T cells
Granules
(like endoscopes and lysomes) contain hydrolytic enzymes and these form phagolysosomes
oxidative burst
rapid uptake of O2–> production of reactive oxygen species
phagocytosis is carried out primarily by
neutrophils and macrophages
Vasodilation definition and what plays an important role in it?
increased permeability of capillaries
- caused by complementary proteins C3a—> releases histamine and this increased permeability of blood vessels
C5 attracts phagocytes to infected areas
Diapedesis
passage of WBC through the intact wall of the capillaries
Il-1
singling molecule (cytokine) produces by macrophages
- acts on the thermoregulatory center in the brain which turns up the body temp
- signal to the site of the wound
what can sense the presence of endotoxins bc of specific receptors
macrophages, they then secrete Il-1
pyrogen
fever producing molecule by macrophages
when do adaptive defenses come into play? what do they rely on ?
if an infection is prolonged, rely on detection and response to foreign antigens
immune cells (b cells and T cells) have surface receptors specific to ___
individual antigens
once activated by the antigen they recognize, T cells and B cells…?
grow and produce copies of themselves. some differentiate into memory cells
2 types of T cells
effective T helper cells–> activated by HMC II, release cytokines that activate B cells and macrophages
effective cytotoxic T cells–> activated by HMC 1, on any cell, release perforins and granzymes which kill host cells that display foreign antigen on their surfaces
each T cell is specific for one
antigen
APCs include?
macrophages and dendritic cells
if the T cell is specific for the antigen being presented on the ABC, the T cell will become activated and produce ______
interleukin 2 (Il2)–> induces multiplication and differentiation into effector T cells and memory T cells
the major histocompatibility complex (MHC) is an _____________
an antigen presenting molecular complex
All cells have ___, only APC have ____
MHC I, MHC II
APC’s have
MHC II, professional APC also have MHC I
MHC I
expressed by all cells, present antigen that come from inside the cell (important during infection by viruses) Regonized by cytotoxic T cells–> release perforins and granzymes to kill the infected host cells
MHC II
expressed by APC and B cells, presents antigen processed in the phagolysosomes ( form microorganisms that were phagocytksed ) recognized by T helper cells
Cytotoxic T cells recognize what complex? and release what to kill cells?
cells that display foreign antigens on MHC 1 are killed by Cytotoxic T cells
- release perforins and granzymes that kill the cell
Activation of macrophages by helper T cells turn into?
- often called “angry Killer cells” because they have increased phagocytic activity and produce higher levels of hydrolytic enzymes
once activated the helper T cells can activate marcrophages that are presenting antigens for which the T cells are specific
what happens to B cells once activated? and how do they get activated?
once activated by helper T cells release cytokines, B cells multiply and differentiate into plasma cells and memory cells –> plasma cells release specific antibodies
antibodies
group of related proteins- immunoglobulins
antigen binding sites (Fab)
-constant region is Fc which binds to the receptor on macrophages and activates complement
IgG
major circulation antibody
4 functions of antibodies
1) act as opsonins, which increase phagocytosis efficiency
2) bind to toxins, which prevent binding to host cells
3) bind to adhesions, which prevent adhesion to host cells
4) activation of complement
primary response
IgM
secondary response (another contact with he same antigen )
IgG
Aquired active immunity
producing memory cells from the antigenic stimuli, can be natural - like an infection,
or artificial - vaccine
aquired passive immunity
acquiring antiboties from a passive source. no direct expossure to the antigen, immunity achieved by injection
- natural - from birth
or artificial - serum from immune animal
natural immunity
some animals can get it but humans or other species cant
opsonins definition
usually an antigen that binds to the microorganism and increases phagocytic activity
