Immune System Failure: Pathogen Evasion and Immunodeficiency Flashcards
pathogen evasion strategies
serotype diversity antigenic drift antigenic shift gene conversion latency
immune system subversion
endocytic hijacking protein mimicry humoral inhibition inflammation inhibition immunosuppression superantigens
what does evasion mean?
avoiding the immune system
what does subversion mean?
commandeering the immune system
Pathogen Evasion:
-serotype diversity
high genetic variability
not necessarily highly mutable
useful for tracking outbreaks
eg: S. pneumoniae
what is a serotype?
antigenically different strains of the same pathogen
Pathogen Evasion:
-antigenic drift
viral genomes are highly mutable
tied to memory erosion
responsible for vial EPIDEMICS
what is antigenic drift
mutations in the viral genome driven by selective pressure as the virus infects a population
Pathogen Evasion:
-Antigenic shift
responsible for viral PANDEMICS
what is antigenic shift
genetic recombination that leads to significant change in the viral antigens
Pathogen Evasion:
-gene conversion
variable surface glycoproteins(VSG) within a population
- cycling of the VSG
- humoral evasion
- VSG gene rearrangement
- ONE VSG dominate at any time
- a minority will express other VSGs
- Trypansosomes is an example
Pathogen Evasion:
-latency
reside in immune privileged tissue
reduced viral load
absent or reduced interferon response and MHC I exp
NK and CD8 evasion
what causes a recurrent emergence of latent virus
stress
concurrent infection
immunocompromised
what are common viruses that have latency period
CMV VZV EBV HV parvovirus adenovirus
Subversion:
Endocytic hijacking
utilize endocytosis for cellular entry
prevent lysosome fusion
escape phagosomes
survive autolysosomal environment
Subversion:
-antigen mimicry
adult worms coat themselves in host protein
surface antigens are regularly shed
antibody evasion and removal
Subversion:
-viral strategies
express Fc receptors
- prevent complement
- inhibit cytokines
- reduce production of pro inflamm response
- block MCH I class
- immunosuppression
Subversion:
-superantigen
potent toxins that disrupt immune function
- Gram positive bacteria
eg: Staph. aureus, Strep. pyogenes - Non-specific T cell activation(non directed)
- Ab and complement activation
- some thought that this can induce autoimmunity
Primary immunodeficiency
genetically caused immune system deficiency
dominant, recessive and x-linked are what type of immunodeficiency
primary
secondary immunodeficiency
immune deficiency caused by environmental factors
examples of secondary immunodeficiency are chronic disease, immunosuppressive drugs, HIV, toxins T/F
true
what is a dominant immunodeficiency?
you only one dominant allele for deficiency
what is a recessive immunodeficiency?
you need to have two recessive alleles for deficiency
X-linked disorders: X-linked agammaglobulinemia
- Bruton’s tyrosine kinase (BTK) necessary for B-cell signaling
- BTK on X chromosome
- BTK males and homozygous females do not develop B cells
- BTK heterozygous females are carriers(lower B cell response)
Classes of primary immunodeficiency
- humoral (60%) impaired B cells
- cellular (10%) impaired T cells
- combined (20%) both B and T cell problems
- Phagocytic cells (10%)
- Complement (<2%)
HIV leads to AIDS
secondary immunodeficiency
highly mutable
blood and sexual fluid transmission
**TARGETS CD4 T cells
Selective IgA deficiency is the most common type of what primary immunodeficiency
humoral immunity
DiGeorge syndrome, ZAP-70 deficiency, X-linked lymphoproliferative syndrome, chronic mucocutaneous candidasis are what type of primary immunodeficiency?
cellular immunity
Chronic ganulomatous disease, Leukocyte adhesion deficiency and Chediak-Higashi syndrome are what type of primary immunodeficiency?
phagocytic cells
