Lymphocytes , Monocytes , Macrophages
Lymphocytes
Lymphocytes can occasionally be seen in a normal sediment. High counts have been reported in cases of acute allergic interstitial nephritis, rapidly evolutive glomerulonephritis, and graft rejection.
With bright field microscopy, the cell cannot be differentiated from the usual leukocytes. With the PAP stain, the cell is small, as a round nucleus with little cytoplasm.
Monocytes
In a study using monoclonal antibodies, a high number of urinary monocytes has been reported in cases of acute allergic interstitial nephritis and of rapidly evolutive glomerulonephritis. In necrosis, these were rare or absent.
Like the lymphocytes, monocytes cannot be identified with bright field microscopy. With the PAP stain, the cell is larger than a neutrophil and has a characteristic bean shaped nucleus.
Macrophages
The macrophage is, after the fibroblast, the most abundant cell in connective tissue. The activated macrophage is difficult to describe because it has a very variable aspect. This cell often presents itself with so many cytoplasmic inclusions that the cell's structures are completely masked. Inclusions are of several types, but the droplet is the most frequent. A classic easy to identify macrophage, is the giant cell that contains one or two smaller phagocyted cells in its cytoplasm. But this form is exceptional; the majority of the macrophages are of average size with a lot of inclusions. The macrophages are frequent in acute inflammations. The macrophage loaded with fat droplets is frequently found in many body fluids. These are usually related to a chronic inflammation process. In urine, when these droplets form a maltese cross when viewed between crossed polarized filters, the macrophages are then called oval fat bodies.
