Parasitic Flashcards
are microorganisms that survive by living off of other organisms, referred to as
hosts.
Parasites
Three types of organisms may cause parasitic infections:
protozoa, helminths, and
ectoparasites
The immune response to parasitic infections differs from that associated with
Bacterial infection
It is described that general concepts need to be considered in relation to host immune
responses to parasites:
(1) Heterogeneity with respect to life cycles and antigenic expression is a key feature of parasitic agents.
(2) Many parasitic infections are chronic in nature.
(3) The mechanisms of immune evasion are significantly different from those of bacterial infections.
(4) Many parasites develop significant genetic and antigenic variation in a relatively short period.
(5) The innate immunity in the natural hosts may be genetically determined.
(6) Humans, as well as animals, differ widely in their ability to handle the complex antigens found in parasites.
Defenses to parasitic infection involve both
both innate and acquired (adaptive) immune
mechanisms
may result in the destruction and removal
of the parasite, thus preventing establishment of an infection.
innate or nonspecific immune response
The nonspecific immune defenses can include activation of cells that may destroy the
parasite by
Phagocytosis
release of cytokines such as:
TNF-α, IL-1, IL-10, IL-12, type I
interferons, and chemokines that enhance the immune response, or activation of the
complement system, resulting in enhanced recognition by the immune system.
No invasion of host by parasite
Natural resistance
Colonization of host with parasite with benefit to both
Symbiosis
Colonization of host with parasite with no benefit or harm
Commensalism
Parasite invades host and causes disease; host develops immunity and is cured
Sterilizing immunity
Parasite invades host and causes disease; host develops an immune response and has some resistance to the parasite but is not cured
Concomitant immunity
Parasite invades host and causes disease; host does not develop resistance to the parasite and is not cured
Ineffective immunity
are best known for their role in allergic reactions.
IgE
IgE Antibodies and Parasites Play an important role in the defense against parasites such as __________ which are too large to be phagocytized.
Helminths
Killing of the parasites is accomplished by
ADCC (Antibody-dependent
cellular cytotoxicity)
bind to specific receptors on the surface of eosinophils, which are then
stimulated to release enzymes from their granules that destroy the parasite.
Fc portions of the parasite-specific IgE antibodies
The concentration of IgE and the number of eosinophils in the peripheral
blood are
Increased or decreased
represent a large heterogeneous group of
eukaryotic organisms that are ubiquitous in the
environment.
Fungi
can either be considered as parasites,
deriving their nutrition from living matter, or
more commonly as saprophytes, living off of
dead and decaying matter.
Fungi
The first line of innate defense includes
skin and the mucous membranes of the respiratory
gastrointestinal
genitourinary tracts
structures and molecules of the organism that are conserved among microbial species.
pathogen-associated molecular patterns (PAMP)
PRRs on the innate immune cells are
phagocytes
macrophages
dendritic cells [DCs]
