Nurse cell

Human physiology
Nurse cells are specialized macrophages residing in the bone marrow, that assist in the development of red blood cells. They absorb the nuclei of immature red blood cells and may provide growth factors to help the red blood cells mature. In the bone marrow, immature red blood cells (erythroblasts) can be seen grouped in a cluster around a nurse cell.

Microbiology
Nurse cell is a term used to describe an infected cell in the disease trichinosis. A trichinella larva enters a cell and develops there, probably as a way of concealing itself from the immune system. The parasite has evolved a way of stimulating blood vessel development around the cell, in order to receive the nutrients it needs. In trichinosis, nurse cells are invariably skeletal muscle cells; this are the only type of cell that can support the parasite.

Nurse cells in respect to drosophilla:

These polytenic germline contribute to the development of the drosophilla oocyte, producing about 250-500 nuclei each 15 of them in each oocyte create 5000 nuclei in total. They dump their cytoplasm containing the nuclei into the oocyte via ring channels.