* White blood cells (WBCs): All types of white blood cells, including neutrophils, lymphocytes, monocytes, eosinophils, and basophils, have a nucleus.

* Red blood cells (RBCs): In mammals, mature red blood cells lose their nucleus during development. However, in other vertebrates, like birds and amphibians, red blood cells retain their nucleus.

So, in summary, all white blood cells have a nucleus, and mature red blood cells in mammals do not, while red blood cells in other vertebrates do.