Final answer:
The TH1 cells are essential in the immunity by activating macrophages through cytokine secretion and ligand binding, which is needed to prevent damage from macrophages to healthy tissues. Their response is typically against intracellular pathogens, and proper regulation of their activity is crucial to avoid unnecessary tissue oxidation and damage.
Step-by-step explanation:
The TH1 cells play a critical role in the immune system by secreting cytokines to activate macrophages and cytotoxic T cells, thus supporting the response against intracellular pathogens like Mycobacterium tuberculosis. The macrophages can lead to tissue damage if they are overactivated, which is why they need to be regulated. The activation involves binding to a certain ligand, whose absence ensures that active macrophages will be turned off to prevent unnecessary tissue damage by oxidative mechanisms and radical release.
T cell activation is a crucial part of the immune response. After pathogens are phagocytized by macrophages, part of the pathogen is presented on the macrophage surface by Major Histocompatibility Complex (MHC) molecules, turning them into antigen-presenting cells. The presented antigens are recognized by T cells, which includes the Helper T cells (TH cells), and in the case of the TH1 response, helps to stimulate the macrophages and improve their ability to destroy the pathogen.
Additionally, during the TH1 response, cytokines secreted by TH1 cells feedback to macrophages and stimulate their digestive capabilities, enabling them to destroy invading bacteria. This regulatory mechanism is essential to manage the innate immune response and prevent it from causing collateral damage to the host's own tissues.