A macrophage or monocyte might present digested bits of a microbe or summon B cells to the site of an infection, but it’s the antibody-secreting B cell that binds some part of the microbe. The cell that carries a receptor which binds the microbe is activated to clonally expand and begins to secrete the antibody into the blood. Finally, that B cell changes its internal landscape and becomes part of the memory B cell compartment, thereby retaining the memory of the original inoculum.
