Adaptive Immunology and Lymphocyte Function Exam: Thymocyte Development, Thymic Selection (Positive & Negative), TCR Gene Rearrangement, DN & DP Thymocytes, cTEC and mTEC Function, AIRE-Mediated Central Tolerance, Lineage Commitment Models (Kinetic, Stoch

Adaptive Immunology and Lymphocyte Function Exam: Thymocyte Development, Thymic Selection (Positive & Negative), TCR Gene Rearrangement, DN & DP Thymocytes, cTEC and mTEC Function, AIRE-Mediated Central Tolerance, Lineage Commitment Models (Kinetic, Stochastic, Instructive), Recent Thymic Emigrants, FOXO1 Regulation, T Cell Activation Signals (TCR, CD28, CTLA4, PD1, ICOS, Signal 3 Cytokines), Immunological Synapse (cSMAC/pSMAC), Cytotoxic and Regulatory T Cells (CTL, Treg, NKT, γδ T cells), B Cell Development, Germinal Center Dynamics (Dark Zone, Light Zone, SHM, CSR, Affinity Maturation), Memory B and T Cells, Plasma Cells, B-1 and Marginal Zone B Cells, TI/TD Antigens, Chemokine Signaling (CCR7, CXCR5, CCL19/21, CXCL13), CD40/CD40L Co-Stimulation, BCR Clustering and Lipid Rafts, Immunoglobulin Classes (IgM, IgG, IgA, IgD, IgE), Apoptotic Pathways (FASL/FAS, Perforin-Granzyme), and BAFF-Mediated B Cell Survival Exam Questions Verified and Provided with Complete A+ Graded Rationales Latest Updated 2026 Thymocytes Immature T cells in thymus Thymus settling progenators (TSP) Thymocyte precursors Multipotent, even after arriving in thymus retain ability to become B,NK, DC, or others Thymus Location of T-cell maturation Organ in chest that shrinks and slows down after puberty Notch Receptor essential in commiting stem cells to the T-cell lineage Notch 1 An overexpression of a constitutively active form in HSCs would favor production of T cells over B cells in BM Double negative thymocytes No CD4 or CD8 Double positive thymocytes Immature T cells in the thymus that are characterized by expression of both the CD4 and the CD8 co-receptor proteins. They represent the majority (about 80%) of thymocytes. Thymic cortex location of T cell positive selection (lymphocyte maturation) Thymic selection Positive and negative selection in the thymus Corticomedulary junction Part of thymus where cortex and medulla meet T cell precursors arrive here from bone marrow, travel to cortex, then medulla if they survive + selection TCR gene rearrangement Occurs in the cortex of thymus at DN3 stage DN1 The first in the four stages in the development of the most immature (CD4-CD8- or double negative) thymocytes. DN1 cells express CD44 but not CD25 and are the progenitors that come from the bone marrow and have the potential to give rise to multiple lymphoid and myeloid cell lineages. DN2 The second in the four stages in the development of the most immature (CD4-CD8- or double negative) thymocytes. Commitment to the T cell lineage and rearrangement of the first TCR receptor genes occur among DN2 cells, which express both CD44 and CD25. T cell development phase I Takes place in thymus Generation of an antigen receptor due to V(D)J gene rearrangement T cell development phase II Takes place in thymus Refinement of Ag receptor repetoire by Positive/negative selection and lineage commitment Positive selection Selection for T-cells that recognize MHC bound antigens Occurs in thymic cortex End result: MHC restriction cTEC Stromal cells of epithelial origin that populate the cortex of the thymus and mediate positive selection of thymocytes. Death by neglect Apoptosis