Cerebriform (Sézary like) mononuclear cells in healthy individuals: a morphologically distinct population of T cells. Relationship with mycosis fungoides and Sézary's syndrome.

The ultrastructural and surface marker characteristics of lymphocytes in human cord blood and peripheral blood of healthy donors were studied with respect to the presence of cerebriform mononuclear cells similar to those occurring in the dermal infiltrate of patients with mycosis fungoides (mycosis cells), and the skin infiltrate and peripheral blood of patients with Sézary's syndrome (Sézary cells). Cerebriform monuclear (Sézary-like) cells are characterized by a high nucleus-cytoplasm ratio, deep and narrow nuclear identations, condensed chromatin at the nuclear membrane and cytoplasm poor in organelles. Of the lymphoid cells in human cord blood and peripheral blood of healthy donors 6.7 and 8.7% respectively proved to be cerebriform mononuclear cells. Since these cells invariably form E-rosettes they are part of the T-cell population in healthy individuals. The finding of similar cells in the skin infiltrate of patch test areas of patients allergic to rubber, formalin and peruvian balsam--an expression of cellular immunity mediated by T-cells--suggests that these cells are reactive T cells. Not all (up to 85%) of the cerebriform mononuclear cells in patients with mycosis fungoides and Sézary's syndrome have T-cell membrane characteristics as shown by E-rosette formation. This suggests the presence of two populations of cerebriform mononuclear cells in mycosis fungoides and Sézary's syndrome. The relationship of cerebriform T cells as seen in healthy individuals with cerebriform or atypical mononuclear cells occurring in the Sézary syndrome and mycosis fungoides is discussed.