Chapter 20 Flashcards
Immunodeficiency diseases are caused by?
congenital or acquired defects in lymphocytes, phagocytes,
and other mediators of adaptive and innate immunity. These diseases are associated with an increased
susceptibility to infection, the nature and severity
of which depend largely on which component of
the immune system is abnormal and the extent of
the abnormality
Disorders of innate immunity include defects
in what?
microbial killing by phagocytes (e.g., CGD
or Chédiak-Higashi syndrome), leukocyte migration and adhesion (e.g., leukocyte adhesion deficiency), TLR signaling, and complement
Severe combined immunodeficiencies include
defects in what?
lymphocyte development that affect
both T and B cells and are caused by defective
cytokine signaling, abnormal purine metabolism,
defective V(D)J recombination, and mutations
that affect T cell maturation
Antibody immunodeficiencies include diseases
caused by what?
defective B cell maturation or activation
and defects in T cell–B cell collaboration (X-linked
hyper-IgM syndrome).
T cell immunodeficiencies include diseases in
which the expression of MHC molecules is what?
defective, T cell signaling disorders, and rare diseases
involving CTL and NK cell functions
Treatment of congenital immunodeficiencies
involves what?
transfusions of antibodies, bone marrow
or stem cell transplantation, or enzyme replacement. Gene therapy may offer improved treatments in the future
Acquired immunodeficiencies are caused by what?
infections, malnutrition, disseminated cancer, and
immunosuppressive therapy for transplant rejection or autoimmune diseases
AIDS is a severe immunodeficiency caused by
infection with HIV. This RNA virus infects what?
CD4+
T
lymphocytes, macrophages, and dendritic cells and
causes progressive dysfunction of the immune
system. Most of the immunodeficiency in AIDS
can be attributed to the depletion of CD4+
T cells
HIV enters cells by binding to both the CD4 molecule and a coreceptor of the chemokine receptor
family. Once it is inside the cell, the viral genome is what?
reverse-transcribed into DNA and incorporated
into the cellular genome. Viral gene transcription
and viral reproduction are stimulated by signals
that normally activate the host cell. Production of
virus is accompanied by death of infected cells
The acute phase of HIV infection is characterized by what?
death of memory CD4+
T cells in mucosal tissues
and dissemination of the virus to lymph nodes. In
the subsequent latent phase, there is low-level
virus replication in lymphoid tissues and slow, progressive loss of T cells
Persistent activation of T
cells promotes their death, leading to rapid loss and what else?
immune deficiency in the chronic phase of the
infection.
CD4+
T cell depletion in HIV-infected individuals
is due to what?
direct cytopathic effects of the virus, toxic
effects of viral products such as shed gp120, and
indirect effects such as activation-induced cell
death or CTL killing of infected CD4+
cells
Several reservoirs of HIV exist in infected individuals, including who?
short-lived activated CD4+
T cells,
longer-lived macrophages, and very long-lived,
latently infected memory T cells
HIV-induced depletion of CD4+
T cells results in
increased what?
susceptibility to infection by a number
of opportunistic microorganisms. In addition, HIVinfected patients have an increased incidence of
tumors, particularly Kaposi’s sarcoma and EBVassociated B cell lymphomas, and encephalopathy
HIV has a high mutation rate, which allows the
virus to evade host immune responses and become
resistant to drug therapies. Genetic variability also
poses a problem for what?
the design of an effective
vaccine against HIV. HIV infection can be treated
by a combination of inhibitors of viral enzymes.
