lec 14- the immune response Flashcards
what are the 2 weapons of the immune system?
-cells that kill/ingest infected or altered cells (e.g. cytotoxic T cells)
soluble proteins that can neutralize, immobilize, or kill pathogens (e.g. antibodies)
what is a pathogen?
a foreign organism
what are the two types of immunity?
-innate (nonspecific)
-adaptive (acquired , involves T and B cells)
what are the two circulatory systems?
cardiovascular and lymphatic
what do lymphatic vessels do?
collect tissue fluid from loose connective tissue, fluid only flows towards the heart
what are leukocytes?
multiple types of white blood cells
what do leukocytes circulate between?
the blood and lymph
what do leukocytes include?
-B cells that make antibodies
-T cells that help B-cells make antibodies
-T cells that can kill virus infected cells
how do cells of the immune system enter the lymphatic system?
by squeezing through specialized endothelial cells in lymph nodes (pathogens can enter through here as well)
what is hematopoiesis?
the regeneration of blood cells
from where do blood cells regenerate?
from the hematopoetic stem cells in the bone marrow
how can leukocytes be differentiated?
by the cell surface molecules identified by monoclonal antibodies
what is CD?
clusters of differentiation between white blood cells (e.g. clusters of T cells is differentiated by whether they express CD4 or CD8)
what are monocytes?
a type of leukocytes/white blood cells that are in the immune system and remove damaged or infected cells
what do monocytes differentiated/turn into?
macrophages
what does the differentiation of monocytes into macrophages involve?
- five to ten-fold enlargement in cell size
- increased complexity and number of intracellular organelles
- increased phagocytic ability
what are macrophages?
long lived (2-4 months), self renewing cells that are the first line of cellular defense against pathogens
how do macrophages defend against pathogens?
in an infection they phagocytose pathogen and secrete signals that recruit monocytes that will turn into more macrophages to expand their population
what do the multiple receptors on a macrophages do and what is the name?
some can recognize patterns on pathogen surfaces, these patterns are known as PAMPs (pathogen associated molecular patterns)
what do the PAMPs on pathogens bind to on macrophages?
they bind to pathogen associated receptors, which then phagocytose the pathogens resulting in the activation of the macrophages
what are the three examples of PAMP receptors?
-Scavenger receptors
-Mannose receptors
-Toll-like receptors (TLR)
what are some other specific receptors?
-Fc receptors
-Complement receptors
how are macrophages activated?
they stay in a rested state until activated by the binding of a pathogen
what are the two primary functions of macrophages?
-phagocytosis of degradation of pathogen, after pathogen binds to phagocytic receptors
-activation of signal trasduction pathway that generates inflammatory cytokines, after pathogen binds to signal receptors
what are cytokines?
substances secreted by cells of the immune system that have an effect on other cells
what are chemokines?
chemokines are a type of cytokine that induce directed chemotaxis
what do cytokines do?
induce inflammation at the site of infection so cells can fight germs there
what presents pathogens to Helper T cells in the context of class II MHC molecules?
macrophages
how do class II MHC proteins travel in the macrophages to present the antigen to T cells?
pieces of the pathogen end up in the binding site of Class II MHC proteins as the MHC proteins travel to the cell surface of a macrophages by the endomembrane system
what are neutrophils?
-white blood cells in the imune system that kill pathogens, they do not present antigens
-most abundant granulocyte
where are neutrophils released from?
they are released from bone marrow and circulate blood stream for 7-10 days
what phagocytoses neutrophils?
macrophages
what are NETs?
-neutrophil extracellular traps
-after a neutrophil has exhausted its ability to phagocytose, it will spit out of a network of extracellular fibres, made of DNA that sticks to pathogens
what substances are in primary and secondary granules?
lytic and bactericidal substances
what is leucocytosis?
an increased number of circulating neutrophils which act as an indication of infection
what do hereditary deficiencies in neutrophil function result in?
an inability to defend against bacterial infections
what are eosinophils?
a type of white blood cells that kill parasites and microorganisms and help protect from allergens, small abundancy in blood stream
what are basophils?
a type of white blood cells that release histamin and interleukins to help cause an allergic reaction, low abundancy in blood stream
what are mast cells?
a type of white blood cells that change upon reacting with histamin and causing an allergic reaction to take place
what are dendritic cells?
a type of white blood cells that engulph pathogens either by phagocytosis or pinocytosis (bulk phase endocytosis), then they migrate via the afferent lymphatic vessels to the nearest regional lymph nodes
what do dendritic cells lose when they are in the lymph nodes?
they lose the ability to do phagocytosis, but gain the ability to present antigen to T cells
what is cross presentation of dendritic cells?
they can present antigens by either using class II MHC or class I MHC proteins, important link between innate and adaptive immune system
what are natural killer cells?
-a type of white blood cells that are large and lack antigen specific receptors
-often the first line of defense against some viruses
what is the summary of the immune response?
-inflammatory response is initiated by cytokine secretion, causing redness, heat and pain which is needed to contain and eliminate infection
- at the same time, signals are being sent to initiate stronger immune response of T and B cells
-adaptive response only come into play if innate response cant clear infection
what are lymphocytes (T and B cells)?
type of white blood cells that are inactive until encountered with antigen, after encounter they become effector cells (have a response for the pathogen)
what is the B cell antigen receptor (BCR)?
a receptor that is the membrane bound form of an antibody that is secreted from B cells upon activation.
what is the T cell antigen receptor (TCR)?
receptors that dont recognize free antigens but only antigens binded to MHC molecules on a antigen-presenting cell
what difference do help T cells and cytotoxic T cells have?
-help T cells have CD4 protein
-cytotoxic T cells have CD8 proteins
what are antigens?
foreign molecules that are recognized by antibodies or receptors
what is the epitope?
the part of the antigen that binds to antibodies or receptors
what happens to B cells when activate?
turn into plasma cells that can make antibodies
what are the antigen presenting cells and what is required for them to present the antigens?
-dendritic cells, macrophages, B-lymphocytes
-need to do phagocytosis to present antigens
what are the 3 types of T cells?
-cytotoxic T cells: have CD8 and kill cells infected with virus
-help T cells: have CD4 and help activate macrophages (and B cells and neutrophils), regulate other white blood cell activities
-regulatory T cells: supress activity of other lymphocytes and help control immune responses
what is class I MHC and class II MHC associated with?
-class I MHC is associated with CD8 and found on every nucleated cell
-class II MHC is associated with CD4 only found on presenting cells
what are lymph nodes an example of?
secondary lymphoid organs
