Lecture 20. intro to blood & immune Flashcards
Cellular components of blood
RBC
WBC( immune cells)
Platelets ( bits of membrane enclosed cytoplasm that aid clotting)
WBC types
- Granulocytes
- Monocytes
- Lymphocyte
antigen
a molecule which induces an immune response via a lymphocyte.
Pathogens have many antigens on their surface.
antibody
a molecular component of the immune system that recognizes and binds (interacts with) antigens.
how do pathogens enter the body
eat- gut
breathe-RT
Touch-skin
Immune system defenses
External innate defense:
Skin, secretions, mucous membrane
Internal innate defense:
Phagocytic cells, natural killer cells, defensive proteins, inflammatory response
Adaptive immunity (activated by exposure to specific pathogens)
- Lymphocytes( B & T cells)
- Antibodies
Internal innate defense reactions
-vasodilation, increased permeability of blood vessels,
Blood cells leave blood vessels and enter the injury site causing redness, heat, and swelling. Inflammation
Phagocytosis of pathogen
Natural killer cell recognition and killing of virus-infected and cancer cells
“Cleanup and repair”
Involves: phagocytic cells, natural killer cells, defensive proteins, inflammatory response
Phagocytosis
Performed by phagocytes, eg. neutrophils,
monocytes/macrophages
-recognize components of bacteria
What is an example of chemicals released by damaged cells that make the blood vessels leaky
histamines
swelling and inflammation-> phagocytosis
Internal Adaptive immune defense/system
-Lymphocytes, antibodies
The adaptive immune response is generated in the lymphatic system,
carried out all over the body.
where do B and T cells develop
B cells – develop and specialize in the bone marrow
-make antibodies
T cells – develop in the bone marrow and mature in the thymus
Both cells need to be activated to function. Activated through the receptors
The cells are specific for each pathogen, receptors give the specificity to lymphocytes
How are B and T cells activated?
exposure to pathogens.
Specific shapes of receptors detect specific pathogens
the cell that deals with the pathogen is cloned and activated
maturation of the immune response- cells improve affinity to antigen over time and exposure
-each lymphocyte represents a different antigen(response to a specific pathogen)
The 2 important features of antigens
- Immunogenicity - the ability to provoke an immune response by stimulating the production of antibodies or T-cells
- Reactivity - the ability of the antigen to react specifically with the antibodies or cells, it provoked.
most antigens have several epitopes that are recognized by antibodies or T cells
epitopes
small parts of the antigen that are recognized by the antibodies
most antigens have several epitopes
~ 7 AA
EG Some parts of the virus are more likely to bind antibodies than others- epitopes
immune cell memory
Memory B cells (and T cells) can live for decades in lymph nodes
Are activated if the body is exposed a second time to the same pathogen
This secondary response is much faster, stronger, and lasts longer than the first
basis of vaccination and induced immunity
What are the common antigens used in serology
The nucleocapsid (N)- inside the virus, becomes visible to the immune system when the virus is internalized. Wraps around RNA inside the virus
Spike (S) Receptor Binding domain. Interacts with host cell receptors
application of antibody tests( Assays)
- Detecting historical infections
isolate blood serum antibodies and see if it’s able to bind the spike protein - Estimating prevalence
- Understanding persistence and protection
Serosurvey
collection and testing of blood from a defined population to estimate the prevalence of antibodies against an infectious pathogen as an indicator of exposure
Serum
blood plasma without the clotting factors
Pathogen
something that causes a disease, eg bacteria or virus
Immunogenic
something which induces an immune response, can be humoral and/or cell-mediated immune response
lymphatic system
is involved in internal innate immunity and adaptive immunity
external innate defense
skin, secretions, mucous membrane
Inflammation
- tissue injury, cells( eg mast cells) release chemical signals such as histamine.
- Dilation and increased leakiness of blood vessels, migration of phagocytic cells to the area
- Phagocytic cells engulf bacteria and debris, and tissue heals
INNATE immune response
What are the phagocytic cells in the blood
neutrophils
macrophages/monocytes
What produces specificity of the B and T cells
randomly produced by rearrangement of the genes coding for the B and T cell antigen receptors
Clonal expansion
antigen activation activated lymphocytes to undergo “clonal expansion”
lymphocyte that responds to the antigen gets replicated and makes more specific lymphocytes
Antibodies and SARS-COV-2
Antibodies induced promptly after infection
-Nucleocapsid and Spike/RBD(receptor binding domain) are the immunodominant antigens and are most commonly used in serology.
The nucleocapsid (N) inside the virus- abundant, wraps the RNA inside the virus. Triggers good antibody response
Spike(S) interacts directly with the host cells
Neutralizing antibodies
the RBD (receptor binding domain) of the Spike protein binds to the ACE2 receptor to infect human cells
-Neutralizing antibodies( Nabs) bind to RBD and block the interaction, stopping the virus from entering human cells.
How can serology testing be used to identify new/historical infections
-if found binding antibodies to the antigen, then the case is most likely historic, since it takes a few weeks for antibodies to be produced
What is a serology test?
an enzyme-linked immunosorbent assay (ELISA)-based test to detect SARS-CoV-2 antibodies in serum or plasma components of blood.
- for any disease, not just covid- identifies antibodies
