Ultrastructural morphometric analysis of nuclear contour irregularity in normal cord and adult blood: correlation with distinct lymphocyte subpopulations.

Cord blood lymphocytes obtained from ten healthy newborns and peripheral blood obtained from ten healthy adults were compared by using ultrastructural morphometric methods. Cord blood lymphocytes could be distinguished from adult lymphocytes on the basis of nuclear contour irregularity (form factor) and perimeter (P less than .001). The mean nuclear form factor (FF) value of the cord lymphocytes, as a group, was 0.603 +/- 0.034; the mean nuclear FF value of adult lymphocytes was 0.755 +/- 0.032. Lymphocyte subpopulations were quantitated by flow cytometric and immunofluorescence techniques and correlated with nuclear contour irregularity (mean FF values) by using linear regression analysis. Overall, the correlations between nuclear contour irregularity and the proportions of distinct lymphocyte subpopulations were opposite for cord and adult blood. Increased nuclear contour irregularity was associated with increased proportions of immature lymphocytes (non-T, non-B lymphocyte population) in the neonate and with increased proportions of T cells in the adult. Of the T cells, increased nuclear contour irregularity showed a better correlation with increased proportions of T helper cells compared with T suppressor cells. A plot of the distribution of FF values indicated two populations of lymphocytes having convoluted and nonconvoluted nuclei, respectively. No true Sézary cells could be identified in cord blood with ultrastructural morphometric criteria, despite the abundance of cerebriform mononuclear cells identified by visual inspection. The lymphocyte with the most irregular nuclear contour was found in an adult and had an FF value of 0.132 (13% of a circle). The contribution of this study to the diagnosis of cutaneous T cell lymphomas and the Sézary syndrome is discussed.