CD4 and infection: Interestingly, before adaptive responses take place, innate lymphoid cells, which can also be divided into ILC1/ILC2/ILC3 subsets, may provide early protection and allow time for adaptive responses, whereas memory and/or memory-phenotype CD4 T cells, by possessing some similar features of ILCs (i.e., a completed differentiation process allowing a rapid response, capable of responding to inflammatory cytokines and tissue residency), may behave similarly as ILCs, to a certain extent, during a subsequent infection [252,253].