Ch. 21 Book Questions Immunodeficiencies Flashcards
RAG-1 gene deficiency is a cause of which of the following immunodeficiency diseases?
a. X-linked Hyper IgM syndrome
b. Severe combined immunodeficiency (SCID)
c. X-linked agammaglobulinemia (XLA)
d. Chronic granulomatous disease (CGD)
e. Leukocyte adhesion deficiency (LAD)
b. Severe combined immunodeficiency (SCID)
RAG-1 and RAG-2 form the V-D-J recombinase that is required for antigen receptor expression and B and T cell development, and deficiency in either RAG protein results in a complete absence of adaptive immunity, i.e. SCID. There are many other causes of SCID, some of which have less complete loss of either T cell or B cell mediated immunity. The X-linked Hyper IgM syndrome is caused by CD40 ligand deficiency; X-linked agammaglobulinemia is caused by Brutons’s PTK deficiency; Chronic granulomatous disease is caused by deficiencies in components of phagocyte oxidase; Leukocyte adhesion deficiencies are caused by lack of leukocyte integrins or ability to synthesize selectin ligands.
A lymph node biopsy from a young boy with X-linked agammaglobulinemia is expected to show which of the following histologic features?
a. Marked perivascular lymphocytic infiltrate
b. Abundant polymorphonuclear inflammation
c. Reduced follicles and germinal centers
d. Nearly absent parafollicular cortical regions
e. Enlarged follicles
c. Reduced follicles and germinal centers
X-linked agammaglobulinemia, or Bruton’s agammaglobulinemia, is an immunodeficiency disease characterized by a block in early B cell maturation and absence of serum Ig. As in other B cell deficiencies, morphology of lymphoid tissues is most remarkable for absent or reduced follicles and germinal centers (i.e., the B cell zones). In contrast, T cell deficiencies usually do not affect follicle size, but follicles will lack germinal centers (because of defective T cell help) and there may be reduced parafollicular cortical regions (i.e., the T cell zones).
Which of the following is the most common known primary immunodeficiency, with a prevalence of 1 in 700 white individuals?
a. X-linked agammaglobulinemia
b. Selective IgA deficiency
c. Common variable immunodeficiency
d. Chronic granulomatous disease
e. Chédiak-Higashi syndrome
b. Selective IgA deficiency
Selective IgA deficiency is the most common (known) primary immunodeficiency and is believed to affect approximately 1 in 700 white individuals. Most cases occur sporadically. Whereas many patients show no clinical symptoms, others experience occasional respiratory infections and diarrhea. In rare cases, patients present with severe, recurrent infections that lead to permanent intestinal and airway damage, with other associated autoimmune disorders.
Which of the following patients is particularly susceptible to infection with Streptococcus pneumoniae, an encapsulated bacterium?
a. A 23-year-old man with malaise, rash, and diffuse lymphadenopathy one week after infection with human immunodeficiency virus
b. A 54-year-old woman receiving local corticosteroid injections for knee pain
c. A 35-year-old man with Hodgkin’s disease and a deficient delayed-type hypersensitivity (DTH) response to Candida antigen
d. A 6-year-old boy with sickle cell anemia who had a splenectomy
e. A 77-year-old woman on chronic renal dialysis and a strict low-protein diet
d. A 6-year-old boy with sickle cell anemia who had a splenectomy
A patient who has undergone splenectomy, or surgical removal of the spleen, is particularly susceptible to infection with encapsulated bacteria such as Streptococcus pneumoniae. This occurs because the spleen is a major site for the phagocytic clearance of opsonized blood-borne microbes and for production of antibodies specific for T cell–independent polysaccharide antigens found in bacterial capsules.
Human immunodeficiency virus (HIV) is NOT a:
a. Herpesvirus
b. RNA virus
c. Enveloped virus
d. Retrovirus
e. Lentivirus
a. Herpesvirus
Human immunodeficiency virus (HIV) is a member of the Lentivirus family of retroviruses. Retroviruses are all enveloped RNA viruses. Herpesviruses are a family of DNA viruses, many of which cause human diseases, including Epstein-Barr virus, cytomegalovirus, herpes simplex virus, and varicella.
All of the following have a direct role in mediating human immunodeficiency virus (HIV) entry into susceptible cells EXCEPT:
a. CD4
b. MHC class I
c. CCR5
d. CXCR4
e. Env
b. MHC class I
Human immunodeficiency virus (HIV) entry into host cells occurs when gp120, a glycoprotein expressed on the HIV envelope, binds to CD4 expressed on host T cells. This induces a conformational change in gp120, promoting its binding to a chemokine coreceptor, such as CCR5 or CXCR4, on host cells. A conformational change in gp41, another glycoprotein expressed on the HIV envelope, exposes a fusion peptide, which inserts into the T cell membrane, allowing fusion of viral and cell membranes and subsequent infection of the host cell. Thus, CD4, CCR5, and CXCR4 are host proteins that are directly involved in mediating HIV entry into susceptible T cells, macrophages, and dendritic cells. Env, the HIV envelope glycoprotein that includes gp120 and gp41, is also directly involved in mediating HIV entry into host cells. In contrast, MHC class I molecules do not have a direct role in this process.
Which is the most reliable indicator for increasing risk of opportunistic infections and other AIDS related disorders in HIV infected individuals?
a. Anti-HIV p24 titers
b. Blood viral load
c. Body weight
d. Blood CD4+ T cell count
e. Blood CD8+ T cell count
d. Blood CD4+ T cell count
The progression to AIDS in patients with HIV infection is best followed by the CD4+ T cell count, and counts less than 200 indicate great risk for opportunistic infections, Kapsosi sarcoma, and lymphomas. Viral load may be high early after infection, and than stay low for many years, becoming high again at the time CD4+ counts drop below 200. CD8+ T cell counts may become low late in disease. Anti-HIV antibodies are detected early and stay high.
