Chapter 13: Failures Of The Body's Defenses Flashcards
Pathogens are under great pressure to evolve mechanism to ______, __________, ________, __________, etc. our immune system.
- evade
- overcome
- trick
- suppress
Sometime our own bodies fail us, due to __________ genetic or ____________ stresses to the immune system that give the pathogen an upper hand.
- inherited
- environmental
Evasion and subversion of the immune system by pathogens
- we have complex responses to pathogens that involve many cellular/molecular interactions between the bug and our immune system
- pathogens can target any of these stages of interaction for its own benefit
Genetic Variation within some species of pathogens prevents effective long-term immunity
- protective immunity towards Streptococcus pneumoniae is serotype-specific
- there are about 90 strains of this bug
- they are called serotypes because antibodies are used to differentiate them
Mutation and recombination allow influenza virus to escape from immunity
- evolution of new influenza variants by antigenic drift
- they escape immunological memory
Antigenic Drift
- causes relatively mild and limited disease epidemic due to point mutation in the gene (hemaglutinin) of the influenza virus
- less worse
Antigenic shift
- can cause pandemics
- virus is structurally quite different from its predecessor and can infect almost everyone
- human influenza virus recombines with another virus on a third host
Trypanosomes use _________ rearrangement to change their surface antigens
- causative agent of sleeping sickness rearranges its surface glycoprotein antigens (VSG)
- antigenic variation by African trypanosomes allows them to escape from adaptive immunity
Herpes viruses persist in human hosts by hiding from the immune response
- herpes simplex virus can become dormant in sensory neurons
- when conditions are right, they come out from the latent state from the trigeminal ganglion via the axon and infect epithelial cells of the lips = cold sore blister
Mycobacterium tuberculosis
- prevents fusion of lysosome with the phagosome
- escapes destruction by the macrophages and can hide in the macrophages
Treponema pallidum
- causative agent of syphilis
- evades specific antibody by coating itself with human proteins
Viruses are great burglars
- in their environment some stole receptors, etc. to neutralize the ligand and intracellular pathways
Bacterial super-antigens stimulate a massive but ineffective T-cell response
- staphylococcal enterotoxins and toxic shock syndrome toxins produced by staphylococcus aureus bacteria can induce a massive T cells proliferation and differentiation up to 20% and eventually apoptosis
Immune responses can contribute to disease
- some pathologies of infection is directly due to the powerful response of the immune system to the infection
- all pathology is due to the immune system when it comes to kids being infected with the Respiratory Syncytial Virus
- alveoli fuse together and kids can’t breathe properly
- increase of mucous production, increased th2 response, recruitment of damaging eosinophils to the area
Bacterial superantigens stimulate a massive but ineffective ______ T cell response
- CD4
Inherited immunodeficiency in genes which reveal themselves by enhanced susceptibility to infection or autoimmunity is…
- primary immunodeficiency disease
________________ __________________ diseases are sue to environmental factor such as immunosuppressive drugs that adversely impact the immune system
- secondary immunodeficiency
Primary Immunodeficiency Diseases
- reveal how the human immune system works
- the mechanisms of immunity and how genes effect the immunity
Inherited immunodeficiency diseases are caused by dominant, recessive or x-linked genes defects
- all primary immunodeficiency diseases can be classified as either dominant, recessive or X-linked
Dominant Defective
- allele show abnormal properties in kids by interfering with activities of the normal allele
Recessive Allele
- function is only elicited when both parents give an abnormal allele to a child
X-linked Diseases
- caused by recessive defects in genes on the x-chromosomes
- males will definitely get the abnormal defect
- females will get the defective phenotype only if both X chromosomes are defective
Recessive and dominant mutations in the interferon-gamma receptor cause diseases of differing severity
- IFN-gamma is a major cytokine that activates macrophages to produce TNFalpha
- is made by NK cells during innate immunity
- is made by th1 CD4 cells and CD8 T cells during adaptive immunity
- IFN-gamma bind to two receptors called IFNgammaR1 and IFNgammaR2 on monocytes
Antibody deficiency leads to an inability to clear extracellular bacteria
- staphylococcus aureus, streptococcus pyogenes, haemophilus influenzae, and streptococcus pneumoniae cannot be recognized by macrophages and neutrophils and thus cleared by antibodies
X-linked agammaglobulinemia (XLA)
- defective protein tyrosine kinase that is involved in growth and differentiation of the pre-B cells
- males will lack mature B cells (no antibodies)
Diminished production of antibodies also results from inherited defects in ______ cell help
- T
- defects in complement components impair antibody responses and cause the accumulation of immune complexes
- the effector functions by antibodies to clear pathogens and antigens are all facilitated by complement activation
Defects in phagocytosis results in enhanced susceptibility to bacterial infection
- phagocytosis by macrophages and neutrophils is the principal method which the immune system removes and destroys bacteria and other microorganisms
- any defect can have profound effect in clearing the infection
Defects in T-cell function result in severe combined immune deficiencies (SCIDs)
- whereas B cells contribute only to the antibody response, T cells function in all aspects of adaptive immunity
- T-cell deficient patients will have a broader ranger of susceptibility to infections than those with B-cell defiencies
Severe combined immune deficiency (SCID)
- people who make neither T cell dependent antibody response nor cell-mediated immune responses have SCID
Transplantation of hematopoietic stem cells
- is used to correct genetic defects of the immune system (bone marrow)
- success of bone marrow transplant is directly correlated with the degree of HLA matching between patient and donor
Graft vs. host disease (GVHD)
- when the mature T cells of donor attacks tissue of recipient
- the donor and recipient must share at least one HLA class 1 allotype and one class 2 allotype in order for the reconstitute T cells to respond to antigens presented by the APC
Human Immunodeficiency Virus (HIV)
- retrovirus that causes slowly progressing disease
- infects CD4 T cells, macrophages and dendritic cells
- gp120 of HIV tightly binds to CD4 molecules for infection of immune cell
Reverse Transcriptase copies the ____ genome into dsDNA that integrates as provirus into the host cell chromosome
- RNA
Acquired Immune Deficiency Syndrome (AIDS)
- Seraconversion is when a patient have detectable level of antibodies against HIV in their serum
- initially HIV level in blood drops due to antibodies
- after infection with HIV there is a gradual extinction of CD4 T cells
- T cell count below 200 cells/ul the patient is said to have AIDS
HIV infection leads to opportunistic infections
- HIV escapes the immune response and develops resistance to antiviral drugs by rapid mutation
