All flashcards
Flashcard 1: Which organ is the primary site of T cell maturation?
Answer: Thymus. Provides a specialized environment for T lymphocyte development and selection to ensure self-tolerance.
Flashcard 2: Which organ is the primary site of B cell maturation in humans?
Answer: Bone marrow. Serves as the hematopoietic site where B lymphocytes undergo maturation and antigen-independent differentiation.
Flashcard 3: Which T cell subtype primarily coordinates immune responses via cytokines?
Answer: CD4+ helper T cells. Interact with MHC II on APCs to secrete cytokines that direct other immune cells' functions.
Flashcard 4: What is the primary role of regulatory T cells (Treg) in immune function?
Answer: Suppress immune responses and maintain self-tolerance. Produce inhibitory cytokines like IL-10 to prevent autoimmunity and excessive inflammation.
Flashcard 5: What is the key structural feature that ensures one-way flow in lymphatic vessels?
Answer: One-way valves (with skeletal muscle and pressure aid). Prevents backflow and promotes unidirectional movement toward the heart, aided by external compression.
Flashcard 6: What is the function of lymph nodes in the immune response?
Answer: Filter lymph and provide sites for immune cell activation. Trap pathogens and antigens in lymph, facilitating lymphocyte interaction and adaptive immune initiation.
Flashcard 7: What is the function of the spleen in immunity and blood maintenance?
Answer: Filters blood; removes old RBCs; mounts immune responses to blood antigens. Acts as a blood filter in the white pulp for immune surveillance and red pulp for erythrocyte recycling.
Flashcard 8: What is the role of lacteals in the lymphatic system?
Answer: Absorb dietary lipids as chyle from intestinal villi. Specialized lymphatic capillaries in the small intestine transport emulsified fats bypassed by blood capillaries.
Flashcard 9: What is the function of the right lymphatic duct?
Answer: Drains right head/arm and right thorax into right subclavian vein. Collects lymph from the right upper quadrant to return it to venous circulation at the brachiocephalic vein junction.
Flashcard 10: Which antibody class is first produced in a primary immune response?
Answer: IgM. Appears earliest due to its pentameric structure enabling strong initial agglutination before class switching.
Flashcard 11: What is the function of plasma cells in humoral immunity?
Answer: Secrete large amounts of antigen-specific antibodies. Arise from activated B cells to produce high-affinity antibodies for humoral defense.
Flashcard 12: What is the function of the thoracic duct?
Answer: Drains most of the body into the left subclavian vein. Serves as the main lymphatic drainage pathway, emptying into the venous system to maintain overall fluid balance.
Flashcard 13: What is the defining feature of innate immunity compared with adaptive immunity?
Answer: Innate is rapid and nonspecific; adaptive is specific with memory. Innate provides immediate defense against broad pathogens, while adaptive develops targeted responses over time.
Flashcard 14: Which immune cells are professional antigen-presenting cells (APCs) in MCAT context?
Answer: Dendritic cells, macrophages, and B cells. Express high levels of MHC II and costimulatory molecules to effectively activate naive T cells.
Flashcard 15: What is the primary immune function of neutrophils?
Answer: Phagocytose and kill bacteria; first responders in acute inflammation. Dominate early inflammatory responses by engulfing microbes and releasing antimicrobial enzymes.
Flashcard 16: What is the primary immune function of eosinophils?
Answer: Defense against helminths; contribute to allergy/asthma. Release granule contents to combat large parasites and modulate type I hypersensitivity reactions.
Flashcard 17: What is clonal selection in adaptive immunity?
Answer: Antigen activates specific lymphocyte clones to proliferate and differentiate. Ensures efficient adaptive responses by expanding only lymphocytes with matching antigen receptors.
Flashcard 18: What is lymph, in terms of its origin and composition?
Answer: Interstitial fluid collected into lymphatic vessels. Forms from plasma filtrate that escapes capillaries, containing water, proteins, and lipids but fewer cells than blood.
Flashcard 19: What is the primary function of the lymphatic system in fluid balance?
Answer: Returns interstitial fluid (lymph) to the bloodstream. Maintains fluid homeostasis by recycling excess fluid and proteins from tissues back to circulation, preventing edema.
Flashcard 20: What is the primary immune function of basophils (and related mast cells)?
Answer: Release histamine and heparin; mediate allergic inflammation. Initiate immediate hypersensitivity by degranulating in response to allergens or IgE crosslinking.
Flashcard 21: What is the primary immune function of macrophages?
Answer: Phagocytosis and antigen presentation; cytokine secretion. Bridge innate and adaptive immunity by processing antigens and activating T cells in tissues.
Flashcard 22: What is the primary immune function of natural killer (NK) cells?
Answer: Kill virus-infected and tumor cells without prior sensitization. Provide innate surveillance by inducing apoptosis in stressed cells via perforin and granzymes.
Flashcard 23: What is the key difference between MHC class I and MHC class II antigen presentation?
Answer: MHC I: endogenous to CD8+; MHC II: exogenous to CD4+. MHC I displays intracellular peptides to cytotoxic T cells; MHC II presents extracellular peptides to helpers.
Flashcard 24: Which T cell subtype directly kills infected cells via perforin and granzymes?
Answer: CD8+ cytotoxic T cells. Recognize MHC I-antigen complexes and eliminate compromised cells to contain infections.