immunity Flashcards
what is the function of the immune system
Defends the body against invading pathogens
Destroys abnormal/mutant cells within the body (e.g. control of cancer)
Removes ‘worn-out’ cells
what are harmful effects of the immune system
Allergies / autoimmune diseases
Tissue rejection.
give examples of Infection-causing organisms (Pathogens)
BACTERIA- Staphylococcus aureus (causes sepsis)
PARASITE - Tapeworm
FUNGUS Epidermophyton floccosum (Athlete’s foot)
name soluble mediators
Cytokines & chemokines
Complement proteins
what are the central lymphoid tissues
bone marrow (B cell development) and thymus (T cell development)
name peripheral lymphoid tissues
Spleen
Lymph nodes
Gut-associated lymphoid tissue (GALT)
[Peyer’s Patches]
Adenoids
Appendix
Tonsils
what is a neutrophil
white blood cell
Destroy bacteria by phagocytosis
first defender on scene
Scavenge to clean up debris
Most abundant leukocyte (60-70%)
what is a Eosinophil
white blood cell
Internal parasite infestations, such as worms: attach to worm
and secrete substances to kill it
what is a monocyte
white blood cell
Mature and enlarge in resident tissue and become known as
macrophages (“large eaters”)
Emerge from bone marrow while still immature
what is phagocytosis
a cell engulfs large particles, such as bacteria, dead cells, or debris, by wrapping its membrane around them to form a phagosome (vesicle). This vesicle then fuses with a lysosome, where enzymes break down the engulfed material.
what is an example of nonspecifoc immunity
Phagocytosis, Inflammation
what is nonspecific immunity
Initial & immediate response against invasion by any pathogens
what are the main mechanisms in nonspecific immunity
- Physical barriers (skin,
mucous membranes) - Inflammation & Phagocytosis
(by neutrophils &
macrophages) - Interferon, NK cells
- Complement
what is an example of specific immunity
lymphocytes
what is specific immunity
Comes into play after nonspecific responses have begun.
Responds to specific pathogens on 2nd or later exposure
what are signs of inflammatory response
redness
heat
swelling
pain
what are the stages of inflammatory repsonse
a) phagocytosis by nearby macrophages
b) dilation and increased permeability of capillary
c) containment of bacteria and foreign matter
d) leukocyte proliferation and migration
e) continued activity of recruited leukocytes
what is the result of inflammatory response
detroys invaders
remove debris
prepares for healing and repair
what are the stages of phagocytosis
- Attachment
- Internalisation (0.1 s)
- Degradation (fuses with lysosomes and enzymes (break down bacteria)
- Exocytosis
what is interferon
a group of signaling proteins made and released by host cells in response to the presence of several viruses. a virus-infected cell will release interferons
- Protects other cells from any viruse
- Induces expression of enzymes that prevent viral replication
- Enhances action of NK cells and cytotoxic T cells
what are natural killer cells
Attack virus-infected cells
Cause lysis via release of perforins
source for interferon Y
what is the complement system
made up of a large number of plasma proteins that react with one another to opsonize pathogens and induce a series of inflammatory responses that help to fight infection
Induces lysis of invading microorganisms
Also complements the ability of other immune mechanisms to clear pathogens
what is lysis
the disintegration of a cell by rupture of the cell wall or membrane.
what are the characteristics of specific immunity
- specificity
- diversity
- memory
- self-tolerance
what is specificity in specific immunity
Lymphocytes (B and T cells) bind and respond to foreign molecules known as antigens via antigen receptors
what is diversity in specific immunity
The body possesses millions of lymphocytes that can recognise and respond to millions of antigens
what is memory in specific immunity
1st exposure to an antigen generates lymphocytes & long-lived memory cells – next exposure to the same antigen, memory cells react faster & with stronger response
what is self-tolerance in specific immunity
- Lymphocytes can distinguish ‘self’ (our normal antigens) from ‘non-self’ (antigens from foreign material).
-B or T cells that may detect and attack ‘self’ are usually destroyed in the bone marrow. - This process of self-tolerance fails in autoimmune diseases.
what are B lymphocytes
- Produce antibodies which circulate in blood
- Defend mainly against bacteria toxins and viruses present in body fluids
Responsible for antibody-mediated or humoral immunity
what are T lymphocytes
- Do not produce antibodies
- Directly destroy specific target cells by releasing chemicals that punch holes in the victim cell (cell-mediated immunity)
- Target cells include body cells invaded by viruses and cancer cells
what are the 5 classes of antibodies
IgM IgD IgG IgE IgA
what are the stages of humoral immunity
a) neutralization
b) agglutination
c) opsonization
d) complement activation
e) enhanced NK cell activity
what is Humoral immunity
an aspect of specific immune responses directed at particular antigens.
what is opsonization
a process by which a pathogen is marked for phagocytosis through coating of a target cell with antibodies.
what is agglutination in humoral immunity
when multiple pathogens aggregated (grouped) by antibody molecules
what is neutralization in humoral immunity
when antibodies block the activity of a pathogen
what is complement activation in humoral immunity
when antibodies bound to pathogens activate the complemnt cascade, resulting in lysis of the cell
where and what are helper T cells
Secrete cytokines that enhance the activity of cytotoxic T cells (enhance phagocytosis)
Stimulate development of B cells into plasma cells
Activated by MHC (Class II) on antigen-presenting cell (e.g.
macrophage)
what are cytotoxic T cells
Activated by MHC (Class I) on virus-infected cell
Kill infected cells by lysis (direct action)
describe Antigen presentation and Helper T-cell activation in infected cells
In an infected cell, Class I MHC molecules present antigen at cell surface so cytotoxic T cells can kill the infected cell
describe Antigen presentation and Helper T-cell activation in phagocytic immune cells
Class II MHC molecules present antigen at cell surface so Helper T cells can bind it and secrete cytokines that will amplify the immune response
give an example of an autoimmune disease
Rheumatoid arthritis (RA)
- inflammation and damage to the
cartilage and bone of joints
Multiple sclerosis (MS)
- T cells attack myelin:
- Blurred vision,
- Muscle weakness,
- Ataxia.
