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A patient presents with chronic mucocutaneous candidiasis. Genetic testing reveals a defect affecting the development and function of T helper 17 (Th17) cells. Which cytokine is MOST likely directly impacted by this genetic defect?
IL-4
IFN-ฮณ
IL-10
IL-17
A novel immunodeficiency is characterized by recurrent bacterial infections, particularly with encapsulated bacteria. Serum analysis reveals normal levels of IgG, IgM, and IgA, but significantly reduced levels of complement component C3. Which pathway of complement activation is MOST likely primarily affected?
Classical pathway
Lectin pathway
Alternative pathway
Terminal pathway
Which of the following accurately describes the role of HLA-E in immune regulation?
Presents antigens to CD8+ T cells
Activates NK cell activity
Stimulates antibody production by B cells
Inhibits NK cell activity
A mutation in the gene encoding the autoimmune regulator (AIRE) protein is MOST likely to result in which immunological consequence?
Increased susceptibility to bacterial infections
Impaired isotype switching in B cells
Defective T cell development in the thymus
Development of autoimmunity against tissue-specific antigens
A research study investigates the immune response to a novel viral pathogen. It is observed that neutralizing antibodies are generated within the first week of infection, but cytotoxic T cell responses are delayed, appearing only after two weeks. Which of the following is the MOST likely explanation for this observation?
The virus infects and depletes T cells initially.
The virus evades MHC class I presentation, delaying CTL responses.
Antibody responses are T-independent while robust CTL responses require T cell help.
The virus replicates primarily in B cells, promoting antibody production.
Individuals with defects in the C1 inhibitor protein are prone to hereditary angioedema. Which of the following BEST describes the underlying mechanism of this condition?
Defective phagocytosis by neutrophils and macrophages
Impaired antibody production by B cells
Overproduction of histamine by mast cells
Unregulated activation of the complement system leading to increased bradykinin production
A patient presents with recurrent opportunistic infections, persistent lymphadenopathy, and a drastically reduced CD4+ T-cell count. Which of the following stages of HIV infection does this MOST accurately represent?
Acute HIV infection
Clinical latency
AIDS
Seroconversion
Which of the following is NOT a typical opportunistic infection seen in AIDS patients?
Pneumocystis pneumonia (PCP)
Kaposi's sarcoma
Toxoplasmosis
Influenza
A patient with advanced HIV infection develops a rapidly progressing brain lesion caused by a eukaryotic parasite. Which of the following is the MOST likely causative agent?
Mycobacterium tuberculosis
Candida albicans
Toxoplasma gondii
Cryptococcus neoformans
Which of the following immunological markers is the MOST reliable indicator for the progression from HIV infection to AIDS?
Presence of HIV antibodies
Viral load above 10,000 copies/mL
CD4+ T-cell count below 200 cells/mmยณ
Decreased levels of immunoglobulins
