T-helper Responses

Macrophage phagocytose toxins, bacteria, or viral particles.The particles are broken down to the level of peptides. The peptides are then "presented" on the cell's (not all cell, only special cells like macrophage) surface by MHC class II molecules to T-cells. Those T-cells that have a specific T-cell receptor, that can recognize the peptide presented in the groove of the MHC class II molecule, will become activated. The activated cell will replicate (clonal expansion) and its desendents will mature to for T-helper cells that will secrete either Th1 or Th2 (T-helper1, T-helper2) cytokines.

The Th1 cytokines promote an inflammatory response such as is needed to fight intracellular parasites like tuberculosis, legionella, and leishmania.

The Th2 cytokines help promote B-cells and the humoral response which produces antibodies.

 

Cytotoxic T-cell response

Cytotoxic T-cells are activated in response to MHC class I molecules (found on all cells). Cytotoxic T-cells kill other cells. They make special molecules that make holes in the targeted cells and kill them.