Overview
This lecture covers lymphocytes, focusing on their types, development, and roles in the immune response, as well as related concepts like stem cells, leukemia, and disease monitoring.
Lymphocyte Basics
- Lymphocytes are smaller than phagocytes and have large nuclei.
- Two main types: B lymphocytes (B cells) and T lymphocytes (T cells).
- B cells mature in the bone marrow; T cells mature in the thymus (not to be confused with the thyroid).
- Mature lymphocytes circulate between blood and lymph to encounter pathogens.
B Cells
- Each B cell produces one specific type of antibody, making them highly specialized.
- When exposed to a matching antigen, B cells clone themselves to increase antibody production.
- Some B cells become plasma cells, which secrete large quantities of antibodies quickly but die soon after.
- Other B cells become memory cells, which "remember" antigens for faster response upon re-exposure.
- Memory B cells enable rapid, symptom-free responses to previously encountered pathogens.
T Cells
- Two main types: Helper T cells and Killer (Cytotoxic) T cells.
- T cells have surface receptors (e.g., CD4) that recognize specific antigens.
- Helper T cells release cytokines to stimulate B cells and macrophages.
- Killer T cells detect and destroy infected body cells by attaching to them and releasing toxic substances.
- HIV targets and destroys Helper T cells, weakening immune response.
Immune Response Indicators
- Bacterial infections/inflammation increase neutrophil numbers, which die at infection sites and form pus.
- Viral infections or tuberculosis increase lymphocyte numbers.
- HIV infection is monitored by tracking T cell counts; lower counts indicate disease progression.
Stem Cells and Leukemia
- Blood cells originate from two stem cell types: myeloid (produces neutrophils, monocytes, platelets) and lymphoid (produces lymphocytes).
- Leukemia is cancer of stem cells, leading to rapid division without proper maturation, reducing normal blood cell counts.
- Leukemia affects the body's ability to produce red blood cells, platelets, and mature white blood cells.
Key Terms & Definitions
- Lymphocytes — White blood cells involved in immune responses (includes B and T cells).
- B Cell — Lymphocyte that produces antibodies specific to antigens.
- T Cell — Lymphocyte involved in cell-mediated immunity (includes Helper and Killer types).
- Antibody — Protein produced by B cells that binds to specific antigens.
- Plasma Cell — B cell derivative that secretes large amounts of antibodies.
- Memory Cell — B or T cell that retains antigen information for faster future response.
- Cytokine — Chemical signal released by Helper T cells to activate other immune cells.
- CD4 — Receptor on Helper T cells that HIV uses to invade.
- Leukemia — Cancer of blood-forming stem cells, disrupting normal blood cell production.
Action Items / Next Steps
- Research and summarize how B cells develop and mature.
- Review videos on phagocytosis and animal transport systems for full context.
- Read more about stem cells and leukemia.
- Prepare for next lecture on active vs passive immunity and immune response stages.