What is the difference between primary cell culture and cell line?

Primary cell culture is the culture of cells directly isolated from parental tissue of interest; whereas cell line is the culture of cells originated from a primary cell culture, which is generally used to expand cell population and prolong life span. These two processed differ in a few aspects.

• Resemblance to parental tissue: Cells in primary culture closely resemble the parental tissue, while cells in a cell line might have mutations or genetic alterations during sub-culturing.
• Process of obtaining cells: In primary cell culture, cells are isolated from tissues, which usually go through phases of rinsing, dissection, mechanical or enzymatic disaggregation, and separation. In contrast, obtaining cells for a cell line is much more straightforward, which are directly transferred from the primary cell culture. If the primary cell is an adherent type, a detaching step is required.
• Life span: Primary cell cultures have finite life spans because the growth of cells exhausts substrate and nutrients, during which toxic metabolites are also accumulated, leading to the death of cells. However, cell lines have prolonged lifespan. Periodic sub-culturing can even produce immortal cells through transformation or genetic alteration of primary cells.
• Risk of contamination: Primary cell cultures are more difficult to take care of, which has a higher risk of contamination than the cell line.