The glycocalyx of epidermal keratinocytes from psoriatic patients has been investigated by means of lectins. Striking changes were found in the levels of glucose and/or mannose (concanavalin A) and of N-acetylglucosamine and/or sialic acid (wheat germ agglutinin) on the surface of cells from the psoriatic lesion. Smaller but significant changes were seen in the clinically uninvolved epidermis of the patient. A marked increase in the affinity of the cell surface for Ulex europus agglutinin (fucose-specific) confirms our previous reports of structural alterations in fucose-containing oligosaccharides in psoriasis.

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A substantial proportion (20-50%) of radioactive sugar incorporated into glycoconjugates by normal human keratinocytes was soluble in chloroform-methanol; using (14C)-galactose as precursor about half of this fraction was neutral lipid. The incorporation of labelled sugars into the lipid fraction was consistently increased in keratinocytes derived from psoriatic lesions. The abnormality in fucose metabolism which we reported previously has been confirmed. In particular we have shown that the molecular weight of fucosylated glycopeptides appears to be abnormally high in the untreated psoriatic lesion, possibly reflecting an increased degree of branching. In psoriatic uninvolved epidermis and in treated psoriatic lesions the situation is reversed, the molecular weight being significantly lower than normal.

We report the uptake of four labelled sugars by keratinocytes isolated from normal epidermis, psoriatic 'uninvolved' skin and psoriatic lesions. Our findings include the following: (1) The rate of uptake of all sugars by the psoriatic lesion is increased. (2) This abnormally high uptake diminishes dramatically during 22 h incubation in vitro. (3) There is a striking abnormality in the metabolism of fucose by psoriatic keratinocytes; our data suggest an increased rate of incorporation of fucose into glycoconjugates.

We describe a flow cytometric technique for measuring the percentage of T6-positive cells in suspensions prepared by trypsinization of human epidermis. The value obtained for healthy controls (1.55 +/- 0.52%) corresponds to about 600 T6-positive cells per mm2 of skin surface, a figure in line with histological estimates. No significant change was found in the percentage of T6-positive cells in either the uninvolved or lesional epidermis of untreated psoriatic patients. PUVA treatment resulted in a significant reduction in T6-positive cells. A cyclic fluctuation in the numbers of T6-positive cells was shown to accompany methotrexate administration on a weekly divided dose schedule.