Before revision:  While the clonal selection of the T helper (Th) cells is the simple and established mechanism for learning a better recognition of new pathogens, the question  still remains unexplored is how the Th cells can learn to eliminate them by activating or deactivating appropriate immune cells after recognition .
After revision:  While the clonal selection of the T helper (Th) cells is the simple and established mechanism for learning a better recognition of new pathogens, the question that still remains unexplored is how the Th cells can learn to eliminate them by activating or deactivating appropriate immune cells after recognition .