Mononuclear Cells

MONONUCLEAR CELLS (literally meaning 'single-nucleated'), round cells of lymphoid character with a round or oval nucleus and clearly defined contours of protoplasm, devoid of specific granulation. The designation M. does not, therefore, predetermine either the genesis or the character of the cell, since lymphoid cells can be not only blood lymphocytes (small, medium, and large), but also lymphocytes of histogenous origin, as well as monocytes, lymphoblasts, myeloblasts, and plasma cells. Sometimes mononuclear infiltrates are spoken of, meaning those round-cell infiltrates which consist mainly of medium and large wide-protoplasmic lymphoid or plasma cells. M. are opposed to polynuclears, i.e., multi-nucleated, namely blood leukocytes. Such an opposition should be considered incorrect, since in essence all white blood corpuscles are M., and the morphological distinction between them does not lie in the plane of quantitative changes of nuclei, but in the plane of qualitative changes of their in the sense of segmentation and polymorphism.