MCAT Biological and Biochemical Foundations of Living Systems Flashcards: 3b Lymphatic Immune Systems

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This deck focuses on 3b Lymphatic Immune Systems, giving you a quick way to review the definitions, rules, and examples that matter most for MCAT Biological and Biochemical Foundations of Living Systems.

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Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: 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 2: 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 3: 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 4: 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 5: Which T cell subtype primarily coordinates immune responses via cytokines?

Answer: CD$4^+$ helper T cells. Interact with MHC II on APCs to secrete cytokines that direct other immune cells' functions.

Flashcard 6: 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 7: 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 8: 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 9: 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 10: 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 11: 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 12: 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 13: 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 14: 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 15: What is the key difference between MHC class I and MHC class II antigen presentation?

Answer: MHC I: endogenous to CD$8^+$; MHC II: exogenous to CD$4^+$. MHC I displays intracellular peptides to cytotoxic T cells; MHC II presents extracellular peptides to helpers.

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: Which T cell subtype directly kills infected cells via perforin and granzymes?

Answer: CD$8^+$ cytotoxic T cells. Recognize MHC I-antigen complexes and eliminate compromised cells to contain infections.

Flashcard 18: 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 19: 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 20: 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 21: 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 22: 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 23: 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 24: 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.