Loss of core 2 O-glycan expression by neoplastic CD7⁺ T cells. (A) HUT78, MyLa2059, and HH cell lines derived from patients with SS were analyzed for expression of CD7, CD43, and CD45, the major glycoprotein receptors for galectin-1, and for reactivity with 1D4 mAb that recognizes core 2 O-glycans on human CD43. CEM T-acute lymphoblastic leukemia cells were used as a positive control. (B) Representative patch stage MF lesion with neoplastic Sézary T cells infiltrating the dermis and epidermis. (Bi) Immunohistochemistry with anti-CD7 demonstrates atypical expression of CD7 by Sézary cells seen singly in the dermis (bottom left) and in characteristic microabscesses in the epidermis (center). (Bii) Tumor cells in a microabscess demonstrate cell surface reactivity with anti-CD7 (arrowheads). (Biii) Immunohistochemistry with 1D4 shows that both 1D4⁺ cells (arrowhead) and 1D4^– cells (arrow) are present in a microabscess. (Biv) Characteristic Sézary cells with large, highly convoluted nuclei demonstrate lack of 1D4 reactivity at the cell surface (arrow). Original magnification × 200 (Bi), × 400 (Bii-iii) and × 1000 (Biv).