The Relative Proportion of Different Types of Cells in Blood and Lymphoid Organs of Normal Rats

Abstract

Lymphoid cells, especially the small ones, fixed and stained by the ordinary methods, do not show sufficient morphological differences to be classified according to their relative maturity as is possible with the granular leucocytes. Difference of opinion thus exists over the developmental potency of the small blood lymphoid cells, and the exact stage of development of the small tissue lymphoid cells is not definitely determined. No further progress in our knowledge of these cells is likely to be made by the old methods of fixation and staining for study. Stained with neutral red and janus green supravitally, however, the lymphoid cells present some very important morphological features which may be used as a basis for their finer differentiation. These features are: (1) the degree of opacity of the cytoplasm, (2) the number and size of mitochondria, and (3) the number of neutral red bodies. We have been able to divide the lymphoid cells, irrespective of their sizes, into 3 types, namely: lymphoblasts, intermediate forms, and lymphocytes. The lymphoblasts have opaque cytoplasm, abundant, coarse mitochondria but no, or very few, neutral red bodies. The lymphocytes have clear cytoplasm, fine, scanty mitochondria, but numerous neutral red bodies. The intermediate forms, as their name implies, are morphologically intermediate between the lymphoblasts and lymphocytes, and are therefore presumably older than the lymphoblasts but younger than the lymphocytes. This classification is used in the present supravital study of the lymphoid cells of the blood, spleen and lymph nodes of a large number of normal rats. The relative proportion of cells is fairly constant in all the animals studied. In Tables I and II the average values of the counts on the blood of 20, and those on the lymphoid organs of 7 animals are presented.