Th1 Cells

Summary

T-Helper Type 1 (Th1) cells are a subset of effector helper T-cells that coordinate attacks against intracellular pathogens. Th1 cell differentiation is stimulated by interleukin-12 (IL-12), a cytokine produced by macrophages. Once Th1 cells are formed, they secrete two products: interleukin-2 (IL-2) and interferon-gamma (IFN-gamma). IL-2 stimulates Killer T-cells and NK cells, which go on to directly kill infected cells. However, IL-2 also works in an autocrine fashion to stimulate proliferation of Helper T-Cells, which eventually increases the number of Th1 cells, amplifying the immune response. On the other hand, IFN-gamma activates macrophages. These activated macrophages increase their antigen presenting roles and release of IL-12, which goes back to stimulate Th1 cells. This feedback loop between macrophages and Th1 ensures a robust immune response against intracellular pathogens.

Key Points

• T Helper Type 1 (Th1) Cell
  • Subset of effector (activated) Helper T-cells
  • Generally coordinate immune response against intracellular antigens
  • Induced by Interleukin-2 (IL-2), Interleukin-12 (IL-12)
    • IL-2 also produced by Th1, works in an autocrine fashion
    • IL-12 from macrophages binds to IL-12R to induce differentiation of Th1 cells; defective signalling in IL-12R Deficiency
    • All Th-cell types are cross-inhibitory, so Th1 differentiation is inhibited by IL-4 and IL-10 (cytokines mediating Th2 line)
  • Secretes Interferon gamma (IFN-gamma), and IL-2
    • IL-2 stimulates Killer T-cells and NK cells
    • IFN-gamma activates Macrophages to kill microbes
      • Macrophages also involved in granuloma formation, so Th1 signalling is involved in pathophysiology of granulomas