front 1 Where do lymphocytes go after leaving the bone marrow or thymus? | back 1 They circulate through blood to lymph to secondary lymphoid tissues (lymph nodes, spleen, mucosal tissues) to search for antigen |
front 2 How do lymphocytes (especially T cells) travel through the body? | back 2 Blood → enter lymph nodes via HEVs → scan for antigen → exit via efferent lymphatics → return to blood via thoracic duct |
front 3 What is lymphocyte recirculation? | back 3 Continuous movement of lymphocytes through blood, lymph nodes, lymph, and back to blood |
front 4 What is the general time course of the T cell response? | back 4 0–6 hr antigen capture → 6–24 hr APC migration → 1–2 days T cell activation → 2–4 days proliferation → 4–7 days effector cells exit |
front 5 How does antigen travel to lymph nodes? | back 5 Free antigen via lymph or dendritic cells carrying antigen |
front 6 Which method is most important for T cell activation? | back 6 Dendritic cells carrying antigen |
front 7 How do lymphocytes enter lymph nodes? | back 7 Through HEVs via rolling, activation, adhesion, and diapedesis |
front 8 Where are T cells located in the lymph node? | back 8 Paracortex |
front 9 Where are B cells located in the lymph node? | back 9 Follicles (cortex) |
front 10 Where do APCs go in the lymph node? | back 10 Paracortex (T cell zone) |
front 11 What is the fibroblastic reticular cell (FRC) network? | back 11 Structural scaffold that guides T cells and dendritic cells and distributes chemokines |
front 12 What is S1P? | back 12 Lipid signaling molecule high in blood and lymph |
front 13 What is S1PR1? | back 13 Receptor for S1P on lymphocytes |
front 14 What is the function of S1P | back 14 S1PR1? / Controls lymphocyte exit from lymph nodes |
front 15 How does S1P signaling work? | back 15 Cells follow S1P gradient (low in node → high in blood) to exit |
front 16 What are the 3 signals required for T cell activation? | back 16 Signal 1 (antigen), Signal 2 (costimulation), Signal 3 (cytokines) |
front 17 What molecules are involved in signal 1? | back 17 TCR, MHC, CD4 or CD8, CD3 |
front 18 What molecules are involved in signal 2? | back 18 CD28 (T cell) and B7/CD80/CD86 (APC) |
front 19 What happens if signal 1 occurs without signal 2? | back 19 Anergy or apoptosis (peripheral tolerance) |
front 20 What molecules are involved in signal 3? | back 20 Cytokines (IL-12, IL-4, TGF-β, IL-6) |
front 21 What is paracrine signaling in T cell activation? | back 21 Cytokines from nearby APCs influence T cell differentiation |
front 22 What is autocrine signaling in T cell activation? | back 22 T cells produce IL-2 to stimulate their own proliferation |
front 23 What is IL-2’s role? | back 23 Drives T cell proliferation (clonal expansion) |
front 24 What is the role of PAMP | back 24 PRR interactions? / Determines cytokines released → determines helper T cell type |
front 25 What is the cSMAC? | back 25 Central region of immunological synapse with TCR and signaling molecules |
front 26 What is the pSMAC? | back 26 Peripheral ring with adhesion molecules for stability |
front 27 What is the function of CD3? | back 27 Transmits TCR signal inside the cell |
front 28 What is the function of CD4? | back 28 Binds MHC II and strengthens signaling |
front 29 What is the function of CD8? | back 29 Binds MHC I and supports cytotoxic activation |
front 30 What is the function of CD28? | back 30 Provides costimulatory signal for activation |
front 31 What is the function of CD40? | back 31 Activates APCs and helps B cells via CD40L interaction |
front 32 What is the role of ITAMs? | back 32 Become phosphorylated and initiate signaling cascade |
front 33 What is the role of LCK? | back 33 Tyrosine kinase that phosphorylates ITAMs and starts signaling |
front 34 What are the outcomes of CD3 signaling? | back 34 Cytokine production, proliferation, differentiation |
front 35 What transcription factors are activated? | back 35 NFAT, NF-κB, AP-1 |
front 36 What is CTLA-4? | back 36 Inhibitory receptor that blocks T cell activation |
front 37 How does CTLA-4 work? | back 37 Competes with CD28 for B7 and shuts down activation |
front 38 What is a checkpoint inhibitor? | back 38 Drug that blocks inhibitory signals (CTLA-4, PD-1) |
front 39 What is the effect of checkpoint inhibitors? | back 39 Enhances T cell response against cancer |
front 40 What side effects occur with checkpoint inhibitors? | back 40 Autoimmune-like effects (rash, colitis, hepatitis, etc.) |
front 41 What are intracellular signaling events of T cell polarization? | back 41 Cytokines → JAK-STAT → transcription factors → differentiation |
front 42 What do Th1 cells do? | back 42 Activate macrophages and fight intracellular pathogens |
front 43 What diseases are associated with Th1? | back 43 Autoimmunity and chronic inflammation |
front 44 What do Th2 cells do? | back 44 Activate eosinophils, promote IgE, fight parasites |
front 45 What diseases are associated with Th2? | back 45 Allergies and asthma |
front 46 What do Th17 cells do? | back 46 Recruit neutrophils, fight extracellular bacteria/fungi |
front 47 What diseases are associated with Th17? | back 47 Autoimmune and inflammatory disorders |
front 48 What do Treg cells do? | back 48 Suppress immune responses and maintain tolerance |
front 49 What happens if Tregs are too low or too high? | back 49 Low → autoimmunity, High → cancer immune suppression |
front 50 What is a Treg? | back 50 CD4+ T cell that suppresses immune responses |
front 51 What is the difference between central and peripheral Tregs? | back 51 Central = thymus-derived, Peripheral = induced in tissues |
front 52 What is the phenotype of Tregs? | back 52 CD4+, CD25+, FOXP3+, CTLA-4 |
front 53 How do Tregs suppress immune responses? | back 53 IL-10, TGF-β, consume IL-2, inhibit APCs, suppress T cells |
front 54 What defines a helper T cell subset? | back 54 Polarizing cytokines, master transcription factor, effector cytokines |
front 55 What is T cell polarization? | back 55 Naïve T cell differentiates into specific helper subtype |
front 56 What is reciprocal inhibition? | back 56 Helper T cell subsets suppress each other |
front 57 What is T cell plasticity? | back 57 Ability of T cells to change phenotype |
front 58 How do plasticity and reciprocal inhibition coexist? | back 58 Early flexibility, later commitment |
front 59 What cells do helper T cells help? | back 59 Macrophages, B cells, CD8 T cells, other immune cells |
front 60 How do T cells activate macrophages? | back 60 IFNγ secretion and CD40–CD40L interaction |
front 61 What is the role of MHC class II? | back 61 Presents antigen to CD4 T cells |
front 62 What is the role of IFNγ? | back 62 Activates macrophages and enhances killing |
front 63 What is the role of CD40 | back 63 CD40L? / Strengthens macrophage activation |
front 64 What happens when macrophages are activated? | back 64 Increased killing, ROS production, cytokine release, better antigen presentation |
front 65 What is macrophage polarization? | back 65 Differentiation into M1 or M2 states |
front 66 What do M1 macrophages do? | back 66 Inflammation and pathogen killing |
front 67 What do M2 macrophages do? | back 67 Tissue repair and anti-inflammatory functions |
front 68 How do T cells influence macrophage polarization? | back 68 Th1 → M1, Th2 → M2 |
front 69 What is the relationship between T cells and macrophages? | back 69 Feedback loop where macrophages activate T cells and T cells activate macrophages |