Excessive costimulation of CD3-dependent lymphocyte response by extracellular matrix proteins in severe widespread psoriasis.

Costimulation of anti-CD3-triggered proliferative T-cell responses by type I and type IV collagen and fibronectin was studied in 25 patients with psoriasis and 12 healthy subjects. The stimulation index of anti-CD3-mediated responses in the presence of type I collagen was about half that in the controls. Although the CD3-dependent proliferative response of psoriatic lymphocytes in patients with active widespread plaque psoriasis was reduced by about 50%, costimulatory responses induced by type IV collagen and fibronectin were found to be enhanced in relation to the controls. The degree of costimulation by type IV collagen and fibronectin was related to disease severity. The highest values of the stimulation index were found in patients with a PASI greater than 24, skin involvement of more than 40% of body surface area, and a duration of psoriatic lesions of more than 3 months. The results indicated that in active widespread plaque psoriasis subpopulations of T cells bearing receptors for some extracellular matrix proteins were increased in the peripheral blood. A factor responsible for this phenomenon may be trafficking of T cells through the basement membrane zone of psoriatic lesions, which presumably causes modification of T cell immunological responsiveness after recirculation.