T Helper Lymphocytes are a type of white blood cell.
The term 'helper' implies their role in assisting other cells in the immune system.
Activation of T Helper Cells
T Helper cells start off dormant (inactive).
Activation occurs through interaction with macrophages.
Macrophages are phagocytes that engulf, ingest, and digest pathogens and present antigens on their cell surface.
Antigen Presentation and Clonal Selection
Pathogens are engulfed by macrophages, which then present antigens to T Helper cells.
T Helper cells with complementary receptors bind to antigens, a process called clonal selection.
Activation leads to clonal expansion via mitosis resulting in memory T-helper lymphocytes and activated T-helper lymphocytes.
Role of Activated T Helper Cells
Release cytokines, a type of signaling molecule.
Cytokines stimulate:
B Lymphocytes: Appropriate B cells are stimulated to undergo clonal expansion to produce memory B cells and plasma cells, which secrete antibodies.
T Killer Lymphocytes: Only appropriate T Killer cells are activated to destroy infected cells.
Macrophages: Increase phagocytosis rate.
Importance of Cytokines
They are crucial for cell signaling in the immune response.
Coordinate activities across different immune cells, effectively acting as the "immune system coordinator."
T Helper Cells and the Immune System
T Helper cells can stimulate many immune cells simultaneously.
Without T Helper cells, immune coordination is compromised.
HIV/AIDS and T Helper Cells
HIV targets and destroys T Helper lymphocytes.
Destruction of T Helper cells impairs cytokine production.
This leads to a weakened immune response, resulting in AIDS.
Despite the presence of B lymphocytes, T Killer lymphocytes, and macrophages, the immune response slows down due to lack of coordination.
Conclusion
T Helper lymphocytes are critical for immune system functioning.
They ensure efficient and coordinated immune responses through cytokine production. Without them, as seen in HIV/AIDS, the immune system is severely impaired.