The major internal protein, p27, of a retrovirus-like particle is expressed in blood lymphocytes from psoriatic patients.

Retrovirus-like particles were isolated from the urine of a patient with psoriasis. The major internal protein, p27, in these particles was isolated by immunosorbent chromatography and gel filtration on a Sephacryl S-300 column in 6 M guanidine hydrochloride. The protein was purified to homogeneity as judged by SDS-PAGE. A hyperimmune serum with specificity for p27 was obtained by vaccination of a rabbit with purified p27 antigen. This antiserum was used to examine blood lymphocytes for the expression of p27 antigen by indirect immunofluorescence. Between 0.1 and 1 per cent of the lymphocytes obtained from patients with psoriasis showed a bright cytoplasmatic (and membrane) fluorescence while no p27 positive cells could be detected in the preparations from the healthy controls (frequency less than 0.01 per cent). Among the p27 positive psoriatic cells were lymphocytes with markers for T cells, B cells and NK cells.