How to is a cell dectected as a infected cell-by virus By the White cells ?

Can you please explain your question a little more. I have no idea what you are trying to ask

I'm assuming you're asking: when a cell is infected by a virus, how is it that the body knows that it's infected and to mount an immune response?

If so, it's a somewhat complicated answer, but the simple answer is with the white blood cells.

When a cell is infected by a virus, the cell will recognize that there is foreign proteins and DNA in the cell. When this happens, the cell will display fragments of the foreign protein via molecules called MHC, who are moved to the cell surface when paired with proteins. T cells (a type of white blood cell) have receptors that recognize MHC molecules on cells. When a T cell recognizes a cell that is displaying MHC and foreign molecules, the T cell will destroy the cell.