10. Clonal Expansion and Immunological Memory

Only a few hundred lymphocytes can recognise any one antigen. This episode shows how one of them becomes a clone of about a thousand effector cells in under a week, why most of that clone dies afterwards, and how the survivors, memory cells, make the second response faster, stronger and entirely antigen-specific. In this episode • The problem of numbers: a few hundred matching cells • Two stages: multiply first, specialise second • A naive lymphocyte stops migrating and becomes a lymphoblast • Clonal expansion: 2–4 divisions a day for 3–5 days, about a thousand cells • Effector cells: plasma cells, cytotoxic T cells, helper T cells • Why the first adaptive response takes about a week • Where effector cells go (and why they no longer recirculate) • Contraction, and memory cells • Primary and secondary antibody responses: lag phase, antigen A and antigen B • Why memory is antigen-specific; why we give boosters • Affinity maturation in germinal centres; memory T-cell thresholds • Chapter 1 in one view: innate vs adaptive, B and T cells, the repertoire, clonal selection Chapters 0:00 Welcome 0:22 The problem of numbers 0:57 Two stages: multiply, then specialise 1:16 A naive lymphocyte stops 1:36 The lymphoblast 2:02 Clonal expansion 2:35 Effector cells 2:57 About a week 3:19 Where effector cells go 4:01 Contraction and memory cells 4:27 Why memory is faster 4:43 The primary antibody response 5:24 The secondary response: antigens A and B 5:59 Antigen-specific memory and boosters 6:34 Affinity maturation and memory T cells 7:27 The big picture: innate vs adaptive 7:55 B cells and T cells 8:12 The repertoire and clonal selection 8:38 The whole journey 9:08 Going deeper, and links Next: the series goes deeper, one piece at a time. Everything we make is at rheumatologydigest.org WhatsApp channel (new material first): https://whatsapp.com/channel/0029Vb6P... Icons from Noun Project (CC BY 3.0): Human by Peleg Red; Spleen by Kono Maru; Heart by Cuputo; Lymph nodes by Laymik. For educational purposes only. Rheumatology Digest is made for students and clinicians; it is not medical advice. #immunology #immunologicalmemory #vaccines