IMMUNOLOGY

Detailed explanation-1: -Helper T cells (CD4+) cells provide cues in the form of soluble mediators and receptor–ligand interactions to cells of both the innate and the adaptive immune systems that trigger and modulate their effector function.

Detailed explanation-2: -As key orchestrators and mediators of immunity, CD4 T cells are central to the vast majority of adaptive immune responses. Generated following an immune response, memory CD4 T cells retain pertinent information about their activation environment enabling them to make rapid effector responses upon reactivation.

Detailed explanation-3: -Activated dendritic cells secrete cytokines that influence both innate and adaptive immune responses, making these cells essential gatekeepers that determine whether and how the immune system responds to the presence of infectious agents.