1. A “variant” of a pathogen is defined as:
A. A completely new species
B. A pathogen with genetic
differences but still the same species
C. A pathogen defined
solely by antigenic differences detected by antibodies
D. A new
strain formed by recombination
B. A pathogen with genetic differences but still the same species
2. A serotype is classified based on:
A. Genetic sequence only
B. Unique clinical symptoms
C.
Antigenic differences recognized by antibodies
D. Host range
C. Antigenic differences recognized by antibodies
3. Original antigenic sin refers to:
A. A pathogen’s first infection being the most severe
B. The
immune system using memory responses to the first encountered version
of a pathogen
C. Immune evasion through gene conversion
D.
T-cell exhaustion
B. The immune system using memory responses to the first encountered version of a pathogen
4. Antigenic drift in influenza involves:
A. Gene reassortment
B. Large genetic shifts
C. Point
mutations in HA and NA
D. Mutations only in the M2 protein
C. Point mutations in HA and NA
5. Antigenic shift leads to:
A. Seasonal influenza
B. Yearly vaccine updates
C.
Formation of completely new influenza subtypes
D. Mild
respiratory infections only
C. Formation of completely new influenza subtypes
6. Trypanosomes evade immunity through:
A. Antigenic shift
B. Cytokine storms
C. Gene conversion
of VSG genes
D. Destruction of CD4 cells
C. Gene conversion of VSG genes
7. Superantigens cause immune evasion by:
A. Blocking TCR signaling
B. Destroying B cells
C.
Non-specific activation of large numbers of T cells
D. Hiding
inside macrophages
C. Non-specific activation of large numbers of T cells
8. Which primary immunodeficiency is caused by a BTK mutation?
A. SCID
B. Hyper IgM syndrome
C. X-linked
agammaglobulinemia
D. CVID
C. X-linked agammaglobulinemia
9. Leukocyte Adhesion Deficiency (LAD) is caused by:
A. ADA deficiency
B. CD18 deficiency
C. TAP
mutation
D. FOXP3 mutation
B. CD18 deficiency
10. Which deficiency predisposes to recurrent Neisseria infections?
A. C1 deficiency
B. C3 deficiency
C. C5–C9
deficiency
D. DAF deficiency
C. C5–C9 deficiency
11. HIV gp120 binds to _____ following CD4 attachment:
A. CXCL10
B. IFN-γ
C. CCR5 or CXCR4
D. MHC I
C. CCR5 or CXCR4
12. Which HIV gene encodes reverse transcriptase, integrase, and protease?
A. gag
B. env
C. pol
D. nef
C. pol
Variant
Organism with genetic differences from original.
Strain
Genetically distinct isolate with unique biological properties.
Serotype
Variant distinguished by antigenic differences detected by antibodies
Describe original antigenic sin
The immune system preferentially uses memory responses from its first exposure to a pathogen even if a new variant is different, leading to suboptimal immunity.
antigenic drift
Small point mutations → seasonal flu.
antigenic shift.
Major reassortment events → new subtypes → pandemics.
What is gene conversion and why is it important for immunity?
Switching expressed gene with a silent copy to change surface antigens → immune evasion (e.g., Trypanosome VSG switching).
what are warning signs of primary immunodeficiency?
Recurrent infections, failure to thrive, chronic diarrhea, needing prolonged antibiotics, opportunistic infections, family history
Name structural components of HIV involved in host cell entry.
- gp120: binds CD4 + CCR5/CXCR4
- gp41: mediates membrane fusion
Describe the phases of HIV infection.
- Acute: High viral load, flu-like
- Latency: Gradual CD4 decline
- AIDS: CD4 < 200 or AIDS-defining illness
1. A 2-month-old presents with chronic diarrhea, failure to thrive, and recurrent viral and fungal infections. Labs show profound T- and B-cell deficiency. What is the most likely diagnosis?
SCID
2. A child has delayed umbilical cord separation and recurrent skin infections with no pus formation. Neutrophil counts are high in blood but absent at infection sites. What defect is most likely?
CD18 deficiency → Leukocyte Adhesion Deficiency
3. A patient gets recurrent Staphylococcus aureus and Aspergillus infections. Neutrophils fail the NBT test. Diagnosis?
Chronic Granulomatous Disease (NADPH oxidase defect)
4. A young boy has extremely low IgG, IgA, and IgE but very high IgM. What immunodeficiency is suspected?
Hyper IgM Syndrome (CD40L deficiency)
5. A teenager presents with recurrent respiratory infections, low IgG and low IgA/IgM. Diagnosis?
CVID
6. A patient develops Kaposi sarcoma, oral thrush, and Pneumocystis pneumonia. CD4 count is 150. What stage of HIV infection is this?
AIDS
7. An HIV patient begins ART with a drug that prevents viral genome insertion into host DNA. Which drug class is this?
Integrase inhibitors
8. A farmer bitten by a tsetse fly develops waves of fever every few weeks. Parasite shows different surface proteins at each visit. What mechanism allows this?
Gene conversion of VSGs (Trypanosomes)
1. Which BEST describes antigenic shift in influenza?
A. Gradual accumulation of point mutations
B. Reassortment of
segmented viral genomes
C. Switching of silent gene copies
D. Mutation caused by selective antibody pressure
B. Reassortment of segmented viral genomes
2. A patient infected with influenza A produces a poor response to a newly circulating variant because their immune system relies on memory B cells from their childhood infection. This is an example of:
A. Antigenic drift
B. Antigenic interference
C. Original
antigenic sin
D. Immune tolerance
C. Original antigenic sin
3. Trypanosome antigenic variation occurs through:
A. Antigenic drift in the VSG gene
B. Antigenic shift between
co-infecting parasites
C. Gene conversion events from a library
of silent VSG genes
D. Mutations induced by host enzymes
C. Gene conversion events from a library of silent VSG genes
Which statement about superantigens is TRUE?
A. They bind the peptide-binding groove of MHC II
B. They bind
outside the antigen-binding site and activate many T cells
C.
They induce class switching in B cells
D. They promote tolerance
by inhibiting cytokines
B. They bind outside the antigen-binding site and activate many T cells
5. A pathogen that establishes lifelong latency and reactivates under stress is most likely a:
A. Retrovirus
B. Coronavirus
C. Herpesvirus
D. Picornavirus
C. Herpesvirus
6. A deficiency in the IL-2Rγ chain most strongly affects:
A. Neutrophil migration
B. B-cell maturation
C. T and NK
cell development
D. Complement activation
C. T and NK cell development
7. A newborn with SCID is found to have normal B cell numbers but no functional T cells. Which cause is most likely?
A. ADA deficiency
B. CD40L mutation
C. IL-2Rγ chain
deficiency
D. BTK mutation
C. IL-2Rγ chain deficiency
8. TAP mutations lead to:
A. Loss of CD4 T cells
B. Loss of CD8 T cells due to poor MHC
I presentation
C. Hyper IgM phenotype
D. High IgE and cold abscesses
B. Loss of CD8 T cells due to poor MHC I presentation
9. Which immunodeficiency presents with recurrent catalase-positive infections and granuloma formation?
A. CVID
B. Chronic Granulomatous Disease
C. Hyper IgE
Syndrome
D. Leukocyte Adhesion Deficiency
B. Chronic Granulomatous Disease
C. Hyper IgE Syndrome
10. Hyper IgE syndrome (STAT3 mutation) is characterized by all of the following EXCEPT:
A. High IgE
B. Cold abscesses
C. Eczema
D. Absent
B cells
D. Absent B cells
11. Which disease is characterized by low IgG and low IgA/IgM with recurrent respiratory infections?
A. SCID
B. XLA
C. CVID
D. Hyper IgM
C. CVID
12. In HIV infection, gp41 specifically functions to:
A. Bind CCR5/CXCR4
B. Bind CD4
C. Mediate fusion of the
viral envelope with the host membrane
D. Integrate viral DNA
C. Mediate fusion of the viral envelope with the host membrane
13. The HIV structural protein p24 is part of the:
A. Envelope
B. RNA genome
C. Capsid
D. Polymerase complex
C. Capsid
14. Which gene encodes HIV’s major structural proteins like p24?
A. pol
B. env
C. gag
D. nef
C. gag
15. A patient with HIV has a CD4 count of 180 and develops Pneumocystis pneumonia. This indicates:
A. Acute HIV
B. Clinical latency
C. AIDS
D. Seroconversion
C. AIDS
16. What is the MOST common reason HIV vaccine development is difficult?
A. HIV is a DNA virus
B. HIV has very stable epitopes
C.
HIV mutates rapidly and targets immune cells
D. HIV is non-enveloped
C. HIV mutates rapidly and targets immune cells
17. Which ART class prevents cleavage of viral polyproteins into functional enzymes?
A. Protease inhibitors
B. Integrase inhibitors
C. Fusion
inhibitors
D. CCR5 antagonists
A. Protease inhibitors
18. A mutation in FOXP3 results in:
A. Hyper IgM syndrome
B. APECED
C. IPEX
D. LAD
C. IPEX
19. Which immunodeficiency results in no B cells and therefore no immunoglobulin production?
A. XLA
B. Hyper IgE Syndrome
C. CVID
D. Complement
C5–C9 deficiency
A. XLA
20. Which immunodeficiency is most strongly associated with recurrent Neisseria infections?
A. C1 deficiency
B. C3 deficiency
C. C5–C9
deficiency
D. Properdin deficiency
C. C5–C9 deficiency