Immuno 1
A 32-year-old woman presents with recurrent sinopulmonary infections and a decreased antibody response to vaccines. Flow cytometry shows normal numbers of B cells, but an absence of CD40L expression on T cells. What is the most likely diagnosis?
A) Hyper IgM syndrome
B) Common variable immunodeficiency (CVID)
C) DiGeorge syndrome
D) Chronic granulomatous disease
A - Hyper IgM syndrome
A 45-year-old man is diagnosed with sepsis caused by a Gram-negative bacterial infection. His lab results show increased levels of IL-1, TNF-α, and IL-6. Which of the following is most likely to occur as a result of the actions of these cytokines?
A) Fever, increased vascular permeability, and leukocyte recruitment
B) Inhibition of B-cell activation
C) Suppression of neutrophil activity
D) Activation of the classical complement pathway
A - Fever, increased vascular permeability, and leukocyte recruitment
A 16-year-old with asthma is exposed to cat dander and develops wheezing and dyspnea. Which immune mechanism is most likely involved?
A) IgE-mediated mast cell degranulation
B) Antibody-dependent cytotoxicity
C) Immune complex deposition
D) T-cell–mediated cytotoxicity
A) IgE-mediated mast cell degranulation
A patient with lupus nephritis has diffuse proliferative glomerulonephritis on renal biopsy. What is the underlying mechanism?
A) Cytotoxic T-cell infiltration
B) Immune complex deposition in glomeruli
C) Anti-GBM antibody formation
D) IgA immune complex deposition
B) Immune complex deposition in glomeruli
A 40-year-old woman presents with bilateral joint stiffness worse in the morning, lasting over an hour. Labs show positive RF and anti-CCP antibodies. Which of the following is the primary immunologic process underlying this condition?
A) Neutrophil activation within joints
B) Immune complex deposition in small vessels
C) Cytotoxic T-cell–mediated synovial destruction
D) CD4+ T-cell–driven synovial inflammation and pannus formation
D) CD4+ T-cell–driven synovial inflammation and pannus formation
A 50-year-old man with a history of chronic sinusitis presents with progressive joint pain and swelling. His white blood cell count is normal, but his lymph node biopsy reveals an absence of germinal centers. Which of the following cells is most likely absent or dysfunctional?
A) T helper cells
B) Follicular dendritic cells
C) Plasma cells
D) Naive B cells
B - Follicular dendritic cells
A 65-year-old man is diagnosed with chronic granulomatous disease after recurrent bacterial and fungal infections. His neutrophils fail to produce reactive oxygen species during the respiratory burst. Which enzyme is most likely deficient in his condition?
A) NADPH oxidase
B) Myeloperoxidase
C) Lysozyme
D) Phospholipase A2
A - NADPH oxidase
A patient with hemolytic anemia due to penicillin exposure is experiencing which type of hypersensitivity reaction?
A) Type I
B) Type II
C) Type III
D) Type IV
B) Type II
A postmenopausal woman presents with vertebral compression fractures. Which lab findings are most likely?
A) Normal Ca²⁺, PO₄³⁻, and PTH
B) Low Ca²⁺, high PTH
C) High PO₄³⁻, low PTH
D) Elevated alkaline phosphatase
A) Normal Ca²⁺, PO₄³⁻, and PTH
A 35-year-old woman with systemic lupus erythematosus presents with confusion and right-sided weakness. MRI shows small cortical infarcts. Labs reveal prolonged PTT and a positive VDRL. What is the most likely underlying mechanism of her symptoms?
A) Immune complex deposition in cerebral vessels
B) Platelet consumption secondary to vasculitis
C) Cross-reacting antibodies targeting CNS neurons
D) Antiphospholipid antibodies causing hypercoagulability
D) Antiphospholipid antibodies causing hypercoagulability
A patient is found to have an absence of circulating dendritic cells. Which of the following consequences is most likely to result from this deficiency?
A) Impaired antigen presentation to T-cells
B) Decreased activation of B-cells
C) Reduced macrophage phagocytosis
D) Absent inflammatory response to pathogens
A) Impaired antigen presentation to T-cells
A 9-year-old boy with recurrent upper respiratory tract infections has low immunoglobulin levels. Flow cytometry reveals normal numbers of B cells, but these cells are unable to undergo class switching. Which of the following is most likely defective in this patient?
A) CD40L
B) MHC class II molecules
C) IL-12 receptor
D) LFA-1 integrin
A - CD40L
A bone marrow transplant recipient develops maculopapular rash, diarrhea, and jaundice. Biopsy shows lymphocytic infiltration. Which immune cells are causing this reaction?
A) Host B-cells
B) Donor T-cells
C) Host NK cells
D) Donor macrophages
B) Donor T-cells
A 6-year-old presents with bowed legs, frontal bossing, and a rachitic rosary. Labs show low vitamin D. What is the pathogenesis?
A) Increased osteoclast activity
B) Defective bone mineralization
C) Excess PTH production
D) Collagen type I defect
B) Defective bone mineralization
A 2-year-old boy has had multiple severe bacterial infections, including pneumonia and abscesses with catalase-positive organisms (e.g., S. aureus, Serratia). A dihydrorhodamine (DHR) test reveals absent oxidative burst in neutrophils.
What is the most likely diagnosis?
A) Chediak-Higashi syndrome
B) Chronic granulomatous disease
C) Leukocyte adhesion deficiency
D) Job syndrome
B) Chronic granulomatous disease
A 35-year-old male with a history of chronic infection presents with swollen, tender lymph nodes. Flow cytometry reveals an increase in CD19+ B-cells but a significant decrease in CD3+ T-cells. Which of the following conditions is most likely responsible for this pattern?
A) Severe combined immunodeficiency (SCID)
B) DiGeorge syndrome
C) X-linked agammaglobulinemia
D) Common variable immunodeficiency (CVID)
B) DiGeorge syndrome
A 60-year-old man with a history of autoimmune disease presents with recurrent infections. His lab results show a decrease in both IgG and IgA antibodies. Which of the following best describes the mechanism by which antibodies can enhance immune responses?
A) Opsonization
B) Phagocytosis by eosinophils
C) Activation of the alternative complement pathway
D) Direct killing of pathogens via apoptosis
A - Opsonization
A patient has dry eyes, dry mouth, and positive anti-Ro (SSA) antibodies. Which complication is most concerning?
A) Coronary artery disease
B) B-cell lymphoma
C) Interstitial nephritis
D) Reactive arthritis
B) B-cell lymphoma
A 30-year-old man has dense, brittle bones and recurrent cranial nerve compression. Labs show low calcium and anemia. What is the most likely cause?
A) Increased osteoclast activity
B) Impaired osteoclast function
C) Excess bone resorption
D) Abnormal fibroblast proliferation
B) Impaired osteoclast function
A 3-month-old infant presents with oral thrush, chronic diarrhea, and failure to thrive. There are no palpable lymph nodes. Lab testing shows undetectable T cells, undetectable B cells, and low NK cells. The patient lives in a sterile bubble environment and is awaiting bone marrow transplant.
Which of the following genetic defects is most likely responsible?
A) CD40L deficiency
B) Mutation in recombination activating genes (RAG1/2)
C) BTK gene mutation
D) Defective IL-2 receptor gamma chain (IL2RG)
D) Defective IL-2 receptor gamma chain (IL2RG)
A 40-year-old woman develops a systemic infection and is found to have a marked increase in serum levels of C-reactive protein (CRP). Which of the following is most likely responsible for the elevation of CRP?
A) Activation of the classical complement pathway
B) Stimulation of macrophages to release IL-6
C) Decreased secretion of TNF-alpha
D) Deficiency of mannose-binding lectin
B) Stimulation of macrophages to release IL-6
A 15-year-old boy presents with an autoimmune disorder. Laboratory tests show that his T cells do not respond to foreign antigens, and antigen presentation is severely impaired. Which of the following is most likely to be involved in the antigen presentation defect?
A) TAP transporter
B) IL-6
C) TLR3
D) CD19
A - TAP transporter
A 45-year-old with morning stiffness and bilateral wrist pain has joint erosion on X-ray and positive anti-CCP antibodies. What is the key cytokine driving this disease?
A) IL-2
B) IL-10
C) TNF-alpha
D) IFN-gamma
C) TNF-alpha
A 42-year-old woman presents with 3 months of worsening shortness of breath and mild nonproductive cough, along with progressive fatigue and difficulty rising from a seated position. She denies smoking or prior lung disease. Exam reveals bilateral inspiratory crackles at the lung bases, mild symmetric proximal muscle weakness, and erythematous, scaly papules on her hands, especially over the knuckles.
Lab results:
CK: 850 U/L (↑)
ANA: Positive
Anti–Jo-1 antibody: Positive
ESR: Elevated
Chest X-ray: Bibasilar reticular opacities
High-resolution chest CT: Ground-glass opacities with early fibrosis
Which of the following best explains the underlying pathogenesis of her pulmonary findings?
A) Antibody-mediated complement activation causing dermal capillary necrosis
B) T-cell–mediated destruction of motor end plates leading to fibrosis
C) Immune complex deposition in alveolar capillaries
D) Autoantibody-induced macrophage activation causing alveolar damage
E) Autoimmune inflammation of alveolar walls associated with antisynthetase antibodies
E) Autoimmune inflammation of alveolar walls associated with antisynthetase antibodies
A 58-year-old man with a history of hypertension and atherosclerosis presents to the emergency department with sudden-onset severe abdominal pain out of proportion to physical exam findings. His abdomen is soft but mildly distended with minimal tenderness. Labs reveal leukocytosis and elevated lactate. A CT angiogram shows occlusion of the superior mesenteric artery and patchy segments of bowel wall thickening. He is taken to surgery, where segments of dusky, hemorrhagic small intestine are resected.
Histopathology of the affected bowel reveals loss of nuclei, ghost-like outlines of enterocytes, and eosinophilic cytoplasm, with neutrophilic infiltration and preservation of tissue architecture.
Which of the following best describes the predominant type of necrosis observed in this patient?
A) Liquefactive necrosis
B) Caseous necrosis
C) Coagulative necrosis
D) Fat necrosis
E) Fibrinoid necrosis
C) Coagulative necrosis